Kinetics of surfactant-mediated epitaxy of III-V semiconductors

NASA Astrophysics Data System (ADS)

Grandjean, N.; Massies, J.

1996-05-01

Surfactant-mediated epitaxy (SME) of III-V semiconductors is studied in the case of the GaAs(001) growth using Te as surfactant. To account for the strong surface segregation of Te, a phenomenological exchange mechanism is used. This process explains the reduction of the surface diffusion length evidenced by scanning tunneling microscopy (STM). However, this kinetics effect is observed only for restricted growth conditions: the As surface coverage should be sufficient to allow the exchange process. STM results as well as Monte Carlo simulations clearly show that the group-V element surface coverage plays a key role in the kinetics of SME of III-V semiconductors.

Methods for improved growth of group III nitride semiconductor compounds

DOEpatents

Melnik, Yuriy; Chen, Lu; Kojiri, Hidehiro

2015-03-17

Methods are disclosed for growing group III-nitride semiconductor compounds with advanced buffer layer technique. In an embodiment, a method includes providing a suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. The method includes forming an AlN buffer layer by flowing an ammonia gas into a growth zone of the processing chamber, flowing an aluminum halide containing precursor to the growth zone and at the same time flowing additional hydrogen halide or halogen gas into the growth zone of the processing chamber. The additional hydrogen halide or halogen gas that is flowed into the growth zone during buffer layer deposition suppresses homogeneous AlN particle formation. The hydrogen halide or halogen gas may continue flowing for a time period while the flow of the aluminum halide containing precursor is turned off.

Electronic Materials and Processing: Proceedings of the First Electronic Materials and Processing Congress Held in Conjunction with the 1988 World Materials Congress, Chicago, Illinois, USA, 24-30 September 1988

DTIC Science & Technology

1988-01-01

usually be traced to a combination of new semiconductors one on top of the other, then concepts, materials, and device principles, the process is called...example, growth techniques. New combinations of compound semiconductors such as GaAs have an materials called heterostructures can be made intrinsically...of combinations of metals, have direct energy band gaps that facilitate semiconductor, and insulators. Quantum the efficient recombination of

Shuttle Mission STS-50: Orbital Processing of High-Quality CdTe Compound Semiconductors Experiment: Final Flight Sample Characterization Report

NASA Technical Reports Server (NTRS)

Larson, David J.; Casagrande, Luis G.; DiMarzio, Don; Alexander, J. Iwan D.; Carlson, Fred; Lee, Taipo; Dudley, Michael; Raghathamachar, Balaji

1998-01-01

The Orbital Processing of High-Quality Doped and Alloyed CdTe Compound Semiconductors program was initiated to investigate, quantitatively, the influences of gravitationally dependent phenomena on the growth and quality of bulk compound semiconductors. The objective was to improve crystal quality (both structural and compositional) and to better understand and control the variables within the crystal growth production process. The empirical effort entailed the development of a terrestrial (one-g) experiment baseline for quantitative comparison with microgravity (mu-g) results. This effort was supported by the development of high-fidelity process models of heat transfer, fluid flow and solute redistribution, and thermo-mechanical stress occurring in the furnace, safety cartridge, ampoule, and crystal throughout the melting, seeding, crystal growth, and post-solidification processing. In addition, the sensitivity of the orbital experiments was analyzed with respect to the residual microgravity (mu-g) environment, both steady state and g-jitter. CdZnTe crystals were grown in one-g and in mu-g. Crystals processed terrestrially were grown at the NASA Ground Control Experiments Laboratory (GCEL) and at Grumman Aerospace Corporation (now Northrop Grumman Corporation). Two mu-g crystals were grown in the Crystal Growth Furnace (CGF) during the First United States Microgravity Laboratory Mission (USML-1), STS-50, June 24 - July 9, 1992.

Method for the growth of large low-defect single crystals

NASA Technical Reports Server (NTRS)

Powell, J. Anthony (Inventor); Neudeck, Philip G. (Inventor); Trunek, Andrew J. (Inventor); Spry, David J. (Inventor)

2008-01-01

A method and the benefits resulting from the product thereof are disclosed for the growth of large, low-defect single-crystals of tetrahedrally-bonded crystal materials. The process utilizes a uniquely designed crystal shape whereby the direction of rapid growth is parallel to a preferred crystal direction. By establishing several regions of growth, a large single crystal that is largely defect-free can be grown at high growth rates. This process is particularly suitable for producing products for wide-bandgap semiconductors, such as SiC, GaN, AlN, and diamond. Large low-defect single crystals of these semiconductors enable greatly enhanced performance and reliability for applications involving high power, high voltage, and/or high temperature operating conditions.

Low temperature junction growth using hot-wire chemical vapor deposition

DOEpatents

Wang, Qi; Page, Matthew; Iwaniczko, Eugene; Wang, Tihu; Yan, Yanfa

2014-02-04

A system and a process for forming a semi-conductor device, and solar cells (10) formed thereby. The process includes preparing a substrate (12) for deposition of a junction layer (14); forming the junction layer (14) on the substrate (12) using hot wire chemical vapor deposition; and, finishing the semi-conductor device.

Photoassisted physical vapor epitaxial growth of semiconductors: a review of light-induced modifications to growth processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alberi, Kirstin; Scarpulla, Michael A.

Herein, we review the remarkable range of modifications to materials properties associated with photoexcitation of the growth surface during physical vapor epitaxy of semiconductors. We concentrate on mechanisms producing measureable, utilizable changes in crystalline perfection, phase, composition, doping, and defect distribution. We outline the relevant physics of different mechanisms, concentrating on those yielding effects orthogonal to the primary growth variables of temperature and atomic or molecular fluxes and document the phenomenological effects reported. Based on experimental observations from a range of semiconductor systems and growth conditions, the primary effects include enhanced anion desorption, molecular dissociation, increased doping efficiency, modification tomore » defect populations and improvements to the crystalline quality of epilayers grown at low temperatures. Future research directions and technological applications are also discussed.« less

Photoassisted physical vapor epitaxial growth of semiconductors: a review of light-induced modifications to growth processes

DOE PAGES

Alberi, Kirstin; Scarpulla, Michael A.

2017-11-22

Herein, we review the remarkable range of modifications to materials properties associated with photoexcitation of the growth surface during physical vapor epitaxy of semiconductors. We concentrate on mechanisms producing measureable, utilizable changes in crystalline perfection, phase, composition, doping, and defect distribution. We outline the relevant physics of different mechanisms, concentrating on those yielding effects orthogonal to the primary growth variables of temperature and atomic or molecular fluxes and document the phenomenological effects reported. Based on experimental observations from a range of semiconductor systems and growth conditions, the primary effects include enhanced anion desorption, molecular dissociation, increased doping efficiency, modification tomore » defect populations and improvements to the crystalline quality of epilayers grown at low temperatures. Future research directions and technological applications are also discussed.« less

Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Brebrick, Robert F.; Volz, Martin P.; Burger, Arnold; Dudley, Michael; Matyi, Richard J.; Ramachandran, Narayanan; Sha, Yi-Gao; Volz, Martin P.; Shih, Hung-Dah

2001-01-01

Crystal growth by vapor transport has several distinct advantages over melt growth techniques. Among various potential benefits from material processing in reduced gravity the followings two are considered to be related to crystal growth by vapor transport: (1) elimination of the crystal weight and its influence on the defect formation and (2) reduction of natural buoyancy-driven convective flows arising from thermally and/ or solutally induced density gradient in fluids. The previous results on vapor crystal growth of semiconductors showed the improvements in surface morphology, crystalline quality, electrical properties and dopant distribution of the crystals grown in reduced gravity as compared to the crystals grown on Earth. But the mechanisms, which are responsible for the improvements and cause the gravitational effects on the complicated and coupled processes of vapor mass transport and growth kinetics, are not well understood.

Method of Promoting Single Crystal Growth During Melt Growth of Semiconductors

NASA Technical Reports Server (NTRS)

Su, Ching-Hua (Inventor)

2013-01-01

The method of the invention promotes single crystal growth during fabrication of melt growth semiconductors. A growth ampoule and its tip have a semiconductor source material placed therein. The growth ampoule is placed in a first thermal environment that raises the temperature of the semiconductor source material to its liquidus temperature. The growth ampoule is then transitioned to a second thermal environment that causes the semiconductor source material in the growth ampoule's tip to attain a temperature that is below the semiconductor source material's solidus temperature. The growth ampoule so-transitioned is then mechanically perturbed to induce single crystal growth at the growth ampoule's tip.

Space processing of crystalline materials: A study of known methods of electrical characterization of semiconductors: Bibliography

NASA Technical Reports Server (NTRS)

Castle, J. G.

1976-01-01

A selective bibliography is given on electrical characterization techniques for semiconductors. Emphasis is placed on noncontacting techniques for the standard electrical parameters for monitoring crystal growth in space, preferably in real time with high resolution.

Growth of Bulk Wide Bandgap Semiconductor Crystals and Their Potential Applications

NASA Technical Reports Server (NTRS)

Chen, Kuo-Tong; Shi, Detang; Morgan, S. H.; Collins, W. Eugene; Burger, Arnold

1997-01-01

Developments in bulk crystal growth research for electro-optical devices in the Center for Photonic Materials and Devices since its establishment have been reviewed. Purification processes and single crystal growth systems employing physical vapor transport and Bridgman methods were assembled and used to produce high purity and superior quality wide bandgap materials such as heavy metal halides and II-VI compound semiconductors. Comprehensive material characterization techniques have been employed to reveal the optical, electrical and thermodynamic properties of crystals, and the results were used to establish improved material processing procedures. Postgrowth treatments such as passivation, oxidation, chemical etching and metal contacting during the X-ray and gamma-ray device fabrication process have also been investigated and low noise threshold with improved energy resolution has been achieved.

Ground-based research of crystal growth of II-VI compound semiconductors by physical vapor transport

NASA Technical Reports Server (NTRS)

Volz, M. P.; Gillies, D. C.; Szofran, F. R.; Lehoczky, S. L.; Su, Ching-Hua; Sha, Yi-Gao; Zhou, W.; Dudley, M.; Liu, Hao-Chieh; Brebrick, R. F.;

Suppressing molecular vibrations in organic semiconductors by inducing strain

PubMed Central

Kubo, Takayoshi; Häusermann, Roger; Tsurumi, Junto; Soeda, Junshi; Okada, Yugo; Yamashita, Yu; Akamatsu, Norihisa; Shishido, Atsushi; Mitsui, Chikahiko; Okamoto, Toshihiro; Yanagisawa, Susumu; Matsui, Hiroyuki; Takeya, Jun

2016-01-01

Organic molecular semiconductors are solution processable, enabling the growth of large-area single-crystal semiconductors. Improving the performance of organic semiconductor devices by increasing the charge mobility is an ongoing quest, which calls for novel molecular and material design, and improved processing conditions. Here we show a method to increase the charge mobility in organic single-crystal field-effect transistors, by taking advantage of the inherent softness of organic semiconductors. We compress the crystal lattice uniaxially by bending the flexible devices, leading to an improved charge transport. The mobility increases from 9.7 to 16.5 cm2 V−1 s−1 by 70% under 3% strain. In-depth analysis indicates that compressing the crystal structure directly restricts the vibration of the molecules, thus suppresses dynamic disorder, a unique mechanism in organic semiconductors. Since strain can be easily induced during the fabrication process, we expect our method to be exploited to build high-performance organic devices. PMID:27040501

Suppressing molecular vibrations in organic semiconductors by inducing strain.

PubMed

Kubo, Takayoshi; Häusermann, Roger; Tsurumi, Junto; Soeda, Junshi; Okada, Yugo; Yamashita, Yu; Akamatsu, Norihisa; Shishido, Atsushi; Mitsui, Chikahiko; Okamoto, Toshihiro; Yanagisawa, Susumu; Matsui, Hiroyuki; Takeya, Jun

2016-04-04

Organic molecular semiconductors are solution processable, enabling the growth of large-area single-crystal semiconductors. Improving the performance of organic semiconductor devices by increasing the charge mobility is an ongoing quest, which calls for novel molecular and material design, and improved processing conditions. Here we show a method to increase the charge mobility in organic single-crystal field-effect transistors, by taking advantage of the inherent softness of organic semiconductors. We compress the crystal lattice uniaxially by bending the flexible devices, leading to an improved charge transport. The mobility increases from 9.7 to 16.5 cm(2) V(-1) s(-1) by 70% under 3% strain. In-depth analysis indicates that compressing the crystal structure directly restricts the vibration of the molecules, thus suppresses dynamic disorder, a unique mechanism in organic semiconductors. Since strain can be easily induced during the fabrication process, we expect our method to be exploited to build high-performance organic devices.

Method for reducing or eliminating interface defects in mismatched semiconductor epilayers

DOEpatents

Fitzgerald, Jr., Eugene A.; Ast, Dieter G.

1992-01-01

The present invention and process relates to crystal lattice mismatched semiconductor composite having a first semiconductor layer and a second semiconductor growth layer deposited thereon to form an interface wherein the growth layer can be deposited at thicknesses in excess of the critical thickness, even up to about 10.times. critical thickness. Such composite has an interface which is substantially free of interface defects. For example, the size of the growth areas in a mismatched In.sub.0.05 Ga.sub.0.95 As/(001)GaAs interface was controlled by fabricating 2-.mu.m high pillars of various lateral geometries and lateral dimensions before the epitaxial deposition of 3500.ANG. of In.sub.0.05 Ga.sub.0.95 As. The linear dislocation density at the interface was reduced from >5000 dislocations/cm to about zero for 25-.mu.m lateral dimensions and to less than 800 dislocations/cm for lateral dimensions as large as 100 .mu.m. The fabricated pillars control the lateral dimensions of the growth layer and block the glide of misfit dislocations with the resultant decrease in dislocation density.

Method for reducing or eliminating interface defects in mismatched semiconductor eiplayers

DOEpatents

Fitzgerald, Jr., Eugene A.; Ast, Dieter G.

1991-01-01

The present invention and process relates to crystal lattice mismatched semiconductor composite having a first semiconductor layer and a second semiconductor growth layer deposited thereon to form an interface wherein the growth layer can be deposited at thicknesses in excess of the critical thickness, even up to about 10x critical thickness. Such composite has an interface which is substantially free of interface defects. For example, the size of the growth areas in a mismatched In.sub.0.05 Ga.sub.0.95 As/(001)GaAs interface was controlled by fabricating 2-.mu.m high pillars of various lateral geometries and lateral dimensions before the epitaxial deposition of 3500.ANG. of In.sub.0.05 Ga.sub.0.95 As. The linear dislocation density at the interface was reduced from >5000 dislocations/cm to about zero for 25-.mu.m lateral dimensions and to less than 800 dislocations/cm for lateral dimensions as large as 100 .mu.m. The fabricated pillars control the lateral dimensions of the growth layer and block the glide of misfit dislocations with the resultant decrease in dislocation density.

Method for reducing or eliminating interface defects in mismatched semiconductor epilayers

DOEpatents

Fitzgerald, E.A. Jr.; Ast, D.G.

1992-10-20

The present invention and process relates to crystal lattice mismatched semiconductor composite having a first semiconductor layer and a second semiconductor growth layer deposited thereon to form an interface wherein the growth layer can be deposited at thicknesses in excess of the critical thickness, even up to about 10[times] critical thickness. Such composite has an interface which is substantially free of interface defects. For example, the size of the growth areas in a mismatched In[sub 0.05]Ga[sub 0.95]As/(001)GaAs interface was controlled by fabricating 2-[mu]m high pillars of various lateral geometries and lateral dimensions before the epitaxial deposition of 3500 [angstrom] of In[sub 0.05]Ga[sub 0.95]As. The linear dislocation density at the interface was reduced from >5000 dislocations/cm to about zero for 25-[mu]m lateral dimensions and to less than 800 dislocations/cm for lateral dimensions as large as 100 [mu]m. The fabricated pillars control the lateral dimensions of the growth layer and block the glide of misfit dislocations with the resultant decrease in dislocation density. 7 figs.

Heat flow control and segregation in directional solidification: Development of an experimental and theoretical basis for Bridgman-type growth experiments in a microgravity environment

NASA Technical Reports Server (NTRS)

Witt, A. F.

1986-01-01

Within the framework of the proposed research, emphasis was placed on application of magnetic fields to semiconductor growth systems. It was found that magnetic fields up to 3 kGauss do not affect the growth behavior nor the macro-segregation behavior in the system Ge(Ga). Applied fields are found to significantlty alter the radial dopant distribution, which is attributed to alterations in the spatial orientation of convective cells. Increasing the magnetic field to 30 kGauss is found to have a fundamental effect on dopant segregation. Emphasis is also placed on the potential of KC-135 flights for preliminary studies on the effects of reduced gravity environments on the wetting behavior of semiconductor systems in growth configuration. The limited number of experiments conducted does not allow any conclusions on the merits of KC-135 flights for semiconductor processing research.

Models of Mass Transport During Microgravity Crystal Growth of Alloyed Semiconductors in a Magnetic Field

NASA Technical Reports Server (NTRS)

Ma, Nancy

2003-01-01

Alloyed semiconductor crystals, such as germanium-silicon (GeSi) and various II-VI alloyed crystals, are extremely important for optoelectronic devices. Currently, high-quality crystals of GeSi and of II-VI alloys can be grown by epitaxial processes, but the time required to grow a certain amount of single crystal is roughly 1,000 times longer than the time required for Bridgman growth from a melt. Recent rapid advances in optoelectronics have led to a great demand for more and larger crystals with fewer dislocations and other microdefects and with more uniform and controllable compositions. Currently, alloyed crystals grown by bulk methods have unacceptable levels of segregation in the composition of the crystal. Alloyed crystals are being grown by the Bridgman process in space in order to develop successful bulk-growth methods, with the hope that the technology will be equally successful on earth. Unfortunately some crystals grown in space still have unacceptable segregation, for example, due to residual accelerations. The application of a weak magnetic field during crystal growth in space may eliminate the undesirable segregation. Understanding and improving the bulk growth of alloyed semiconductors in microgravity is critically important. The purpose of this grant to to develop models of the unsteady species transport during the bulk growth of alloyed semiconductor crystals in the presence of a magnetic field in microgravity. The research supports experiments being conducted in the High Magnetic Field Solidification Facility at Marshall Space Flight Center (MSFC) and future experiments on the International Space Station.

Space processing of crystalline materials: A study of known methods of electrical characterization of semiconductors

NASA Technical Reports Server (NTRS)

Castle, J. G.

1976-01-01

A literature survey is presented covering nondestructive methods of electrical characterization of semiconductors. A synopsis of each technique deals with the applicability of the techniques to various device parameters and to potential in-flight use before, during, and after growth experiments on space flights. It is concluded that the very recent surge in the commercial production of large scale integrated circuitry and other semiconductor arrays requiring uniformity on the scale of a few microns, involves nondestructive test procedures which could well be useful to NASA for in-flight use in space processing.

Growth and Characterization of Epitaxial Piezoelectric and Semiconductor Films.

DTIC Science & Technology

1980-07-01

quality epitaxial films at low growth rates. This process is limited to films up to a few microns thickness. The aluminum chloride/ ammonia CVD process has... scrubber through a rotary Vacuum pump maintaining Reactions.-DEZ is an electron deficient compound a pressure of about 400 Torr inside the reaction chain

Temperature Dependence of Density, Viscosity and Electrical Conductivity for Hg-Based II-VI Semiconductor Melts

NASA Technical Reports Server (NTRS)

Li, C.; Ban, H.; Lin, B.; Scripa, R. N.; Su, C.-H.; Lehoczky, S. L.

2004-01-01

The relaxation phenomenon of semiconductor melts, or the change of melt structure with time, impacts the crystal growth process and the eventual quality of the crystal. The thermophysical properties of the melt are good indicators of such changes in melt structure. Also, thermophysical properties are essential to the accurate predication of the crystal growth process by computational modeling. Currently, the temperature dependent thermophysical property data for the Hg-based II-VI semiconductor melts are scarce. This paper reports the results on the temperature dependence of melt density, viscosity and electrical conductivity of Hg-based II-VI compounds. The melt density was measured using a pycnometric method, and the viscosity and electrical conductivity were measured by a transient torque method. Results were compared with available published data and showed good agreement. The implication of the structural changes at different temperature ranges was also studied and discussed.

Coincident site lattice-matched growth of semiconductors on substrates using compliant buffer layers

DOEpatents

Norman, Andrew

2016-08-23

A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a silicon substrate using a compliant buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The compliant buffer material and semiconductor materials may be deposited using coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The coincident site lattice matching epitaxial process, as well as the use of a ductile buffer material, reduce the internal stresses and associated crystal defects within the deposited semiconductor materials fabricated using the disclosed method. As a result, the semiconductor devices provided herein possess enhanced performance characteristics due to a relatively low density of crystal defects.

Organic Single-Crystal Semiconductor Films on a Millimeter Domain Scale.

PubMed

Kwon, Sooncheol; Kim, Jehan; Kim, Geunjin; Yu, Kilho; Jo, Yong-Ryun; Kim, Bong-Joong; Kim, Junghwan; Kang, Hongkyu; Park, Byoungwook; Lee, Kwanghee

2015-11-18

Nucleation and growth processes can be effectively controlled in organic semiconductor films through a new concept of template-mediated molecular crystal seeds during the phase transition; the effective control of these processes ensures millimeter-scale crystal domains, as well as the performance of the resulting organic films with intrinsic hole mobility of 18 cm(2) V(-1) s(-1). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microgravity

NASA Image and Video Library

1987-12-17

The MEPHISTO experiment is a cooperative American and French investigation of the fundamentals of crystal growth. MEPHISTO is a French-designed and built materials processing furnace. MEPHISTO experiments study solidation (also called freezing) during the growth cycle of liquid materials used for semiconductor crystals. Solidification is the process where materials change from liquid (melt) to solid. An example of the solidification process is water changing into ice.

Nanophase diagram of binary eutectic Au-Ge nanoalloys for vapor-liquid-solid semiconductor nanowires growth

NASA Astrophysics Data System (ADS)

Lu, Haiming; Meng, Xiangkang

2015-06-01

Although the vapor-liquid-solid growth of semiconductor nanowire is a non-equilibrium process, the equilibrium phase diagram of binary alloy provides important guidance on the growth conditions, such as the temperature and the equilibrium composition of the alloy. Given the small dimensions of the alloy seeds and the nanowires, the known phase diagram of bulk binary alloy cannot be expected to accurately predict the behavior of the nanowire growth. Here, we developed a unified model to describe the size- and dimensionality-dependent equilibrium phase diagram of Au-Ge binary eutectic nanoalloys based on the size-dependent cohesive energy model. It is found that the liquidus curves reduce and shift leftward with decreasing size and dimensionality. Moreover, the effects of size and dimensionality on the eutectic composition are small and negligible when both components in binary eutectic alloys have the same dimensionality. However, when two components have different dimensionality (e.g. Au nanoparticle-Ge nanowire usually used in the semiconductor nanowires growth), the eutectic composition reduces with decreasing size.

Large-area, laterally-grown epitaxial semiconductor layers

DOEpatents

Han, Jung; Song, Jie; Chen, Danti

2017-07-18

Structures and methods for confined lateral-guided growth of a large-area semiconductor layer on an insulating layer are described. The semiconductor layer may be formed by heteroepitaxial growth from a selective growth area in a vertically-confined, lateral-growth guiding structure. Lateral-growth guiding structures may be formed in arrays over a region of a substrate, so as to cover a majority of the substrate region with laterally-grown epitaxial semiconductor tiles. Quality regions of low-defect, stress-free GaN may be grown on silicon.

One-dimensional ZnO nanostructures.

PubMed

Jayadevan, K P; Tseng, T Y

2012-06-01

The wide-gap semiconductor ZnO with nanostructures such as nanoparticle, nanorod, nanowire, nanobelt, nanotube has high potential for a variety of applications. This article reviews the fundamentals of one-dimensional ZnO nanostructures, including processing, structure, property, application and their processing-microstructure-property correlation. Various fabrication methods of the ZnO nanostructures including vapor-liquid-solid process, vapor-solid growth, solution growth, solvothermal growth, template-assisted growth and self-assembly are introduced. The characterization and properties of the ZnO nanostructures are described. The possible applications of these nanostructures are also discussed.

GaN/NbN epitaxial semiconductor/superconductor heterostructures.

PubMed

Yan, Rusen; Khalsa, Guru; Vishwanath, Suresh; Han, Yimo; Wright, John; Rouvimov, Sergei; Katzer, D Scott; Nepal, Neeraj; Downey, Brian P; Muller, David A; Xing, Huili G; Meyer, David J; Jena, Debdeep

2018-03-07

Epitaxy is a process by which a thin layer of one crystal is deposited in an ordered fashion onto a substrate crystal. The direct epitaxial growth of semiconductor heterostructures on top of crystalline superconductors has proved challenging. Here, however, we report the successful use of molecular beam epitaxy to grow and integrate niobium nitride (NbN)-based superconductors with the wide-bandgap family of semiconductors-silicon carbide, gallium nitride (GaN) and aluminium gallium nitride (AlGaN). We apply molecular beam epitaxy to grow an AlGaN/GaN quantum-well heterostructure directly on top of an ultrathin crystalline NbN superconductor. The resulting high-mobility, two-dimensional electron gas in the semiconductor exhibits quantum oscillations, and thus enables a semiconductor transistor-an electronic gain element-to be grown and fabricated directly on a crystalline superconductor. Using the epitaxial superconductor as the source load of the transistor, we observe in the transistor output characteristics a negative differential resistance-a feature often used in amplifiers and oscillators. Our demonstration of the direct epitaxial growth of high-quality semiconductor heterostructures and devices on crystalline nitride superconductors opens up the possibility of combining the macroscopic quantum effects of superconductors with the electronic, photonic and piezoelectric properties of the group III/nitride semiconductor family.

Design of Ceramic Springs for Use in Semiconductor Crystal Growth in Microgravity

NASA Technical Reports Server (NTRS)

Kaforey, M. F.; Deeb, C. W.; Matthiesen, D. H.

1999-01-01

Segregation studies can be done in microgravity to reduce buoyancy driven convection and investigate diffusion-controlled growth during the growth of semiconductor crystals. During these experiments, it is necessary to prevent free surface formation in order to avoid surface tension driven convection (Marangoni convection). Semiconductor materials such as gallium arsenide and germanium shrink upon melting, so a spring is necessary to reduce the volume of the growth chamber and prevent the formation of a free surface when the sample melts. A spring used in this application must be able to withstand both the high temperature and the processing atmosphere. During the growth of gallium arsenide crystals during the GTE Labs/USAF/NASA GaAs GAS Program and during the CWRU GaAs programs aboard the First and Second United States microgravity Laboratories, springs made of pyrolytic boron nitride (PBN) leaves were used. The mechanical properties of these PBN springs have been investigated and springs having spring constants ranging from 0.25 N/mm to 25 N/mm were measured. With this improved understanding comes the ability to design springs for more general applications, and guidelines are given for optimizing the design of PBN springs for crystal growth applications.

Surface Preparation and Deposited Gate Oxides for Gallium Nitride Based Metal Oxide Semiconductor Devices

PubMed Central

Long, Rathnait D.; McIntyre, Paul C.

2012-01-01

The literature on polar Gallium Nitride (GaN) surfaces, surface treatments and gate dielectrics relevant to metal oxide semiconductor devices is reviewed. The significance of the GaN growth technique and growth parameters on the properties of GaN epilayers, the ability to modify GaN surface properties using in situ and ex situ processes and progress on the understanding and performance of GaN metal oxide semiconductor (MOS) devices are presented and discussed. Although a reasonably consistent picture is emerging from focused studies on issues covered in each of these topics, future research can achieve a better understanding of the critical oxide-semiconductor interface by probing the connections between these topics. The challenges in analyzing defect concentrations and energies in GaN MOS gate stacks are discussed. Promising gate dielectric deposition techniques such as atomic layer deposition, which is already accepted by the semiconductor industry for silicon CMOS device fabrication, coupled with more advanced physical and electrical characterization methods will likely accelerate the pace of learning required to develop future GaN-based MOS technology.

Ferrite film growth on semiconductor substrates towards microwave and millimeter wave integrated circuits

NASA Astrophysics Data System (ADS)

Chen, Z.; Harris, V. G.

2012-10-01

It is widely recognized that as electronic systems' operating frequency shifts to microwave and millimeter wave bands, the integration of ferrite passive devices with semiconductor solid state active devices holds significant advantages in improved miniaturization, bandwidth, speed, power and production costs, among others. Traditionally, ferrites have been employed in discrete bulk form, despite attempts to integrate ferrite as films within microwave integrated circuits. Technical barriers remain centric to the incompatibility between ferrite and semiconductor materials and their processing protocols. In this review, we present past and present efforts at ferrite integration with semiconductor platforms with the aim to identify the most promising paths to realizing the complete integration of on-chip ferrite and semiconductor devices, assemblies and systems.

Vapor-Liquid-Solid Etch of Semiconductor Surface Channels by Running Gold Nanodroplets.

PubMed

Nikoobakht, Babak; Herzing, Andrew; Muramoto, Shin; Tersoff, Jerry

2015-12-09

We show that Au nanoparticles spontaneously move across the (001) surface of InP, InAs, and GaP when heated in the presence of water vapor. As they move, the particles etch crystallographically aligned grooves into the surface. We show that this process is a negative analogue of the vapor-liquid-solid (VLS) growth of semiconductor nanowires: the semiconductor dissolves into the catalyst and reacts with water vapor at the catalyst surface to create volatile oxides, depleting the dissolved cations and anions and thus sustaining the dissolution process. This VLS etching process provides a new tool for directed assembly of structures with sublithographic dimensions, as small as a few nanometers in diameter. Au particles above 100 nm in size do not exhibit this process but remain stationary, with oxide accumulating around the particles.

Compound semi-conductors and controlled doping thereof

NASA Technical Reports Server (NTRS)

Larkin, David J. (Inventor); Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor); Matus, Lawrence G. (Inventor)

1998-01-01

A method of controlling the amount of impurity incorporation in a crystal grown by a chemical vapor deposition process. Conducted in a growth chamber, the method includes the controlling of the concentration of the crystal growing components in the growth chamber to affect the demand of particular growth sites within the growing crystal thereby controlling impurity incorporation into the growth sites.

Perspectives on integrated modeling of transport processes in semiconductor crystal growth

NASA Technical Reports Server (NTRS)

Brown, Robert A.

1992-01-01

The wide range of length and time scales involved in industrial scale solidification processes is demonstrated here by considering the Czochralski process for the growth of large diameter silicon crystals that become the substrate material for modern microelectronic devices. The scales range in time from microseconds to thousands of seconds and in space from microns to meters. The physics and chemistry needed to model processes on these different length scales are reviewed.

Controlled growth of semiconductor crystals

DOEpatents

Bourret-Courchesne, Edith D.

1992-01-01

A method for growth of III-V, II-VI and related semiconductor single crystals that suppresses random nucleation and sticking of the semiconductor melt at the crucible walls. Small pieces of an oxide of boron B.sub.x O.sub.y are dispersed throughout the comminuted solid semiconductor charge in the crucible, with the oxide of boron preferably having water content of at least 600 ppm. The crucible temperature is first raised to a temperature greater than the melt temperature T.sub.m1 of the oxide of boron (T.sub.m1 =723.degree. K. for boron oxide B.sub.2 O.sub.3), and the oxide of boron is allowed to melt and form a reasonably uniform liquid layer between the crucible walls and bottom surfaces and the still-solid semiconductor charge. The temperature is then raised to approximately the melt temperature T.sub.m2 of the semiconductor charge material, and crystal growth proceeds by a liquid encapsulated, vertical gradient freeze process. About half of the crystals grown have a dislocation density of less than 1000/cm.sup.2. If the oxide of boron has water content less than 600 ppm, the crucible material should include boron nitride, a layer of the inner surface of the crucible should be oxidized before the oxide of boron in the crucible charge is melted, and the sum of thicknesses of the solid boron oxide layer and liquid boron oxide layer should be at least 50 .mu.m.

Controlled growth of semiconductor crystals

DOEpatents

Bourret-Courchesne, E.D.

1992-07-21

A method is disclosed for growth of III-V, II-VI and related semiconductor single crystals that suppresses random nucleation and sticking of the semiconductor melt at the crucible walls. Small pieces of an oxide of boron B[sub x]O[sub y] are dispersed throughout the comminuted solid semiconductor charge in the crucible, with the oxide of boron preferably having water content of at least 600 ppm. The crucible temperature is first raised to a temperature greater than the melt temperature T[sub m1] of the oxide of boron (T[sub m1]=723 K for boron oxide B[sub 2]O[sub 3]), and the oxide of boron is allowed to melt and form a reasonably uniform liquid layer between the crucible walls and bottom surfaces and the still-solid semiconductor charge. The temperature is then raised to approximately the melt temperature T[sub m2] of the semiconductor charge material, and crystal growth proceeds by a liquid encapsulated, vertical gradient freeze process. About half of the crystals grown have a dislocation density of less than 1000/cm[sup 2]. If the oxide of boron has water content less than 600 ppm, the crucible material should include boron nitride, a layer of the inner surface of the crucible should be oxidized before the oxide of boron in the crucible charge is melted, and the sum of thicknesses of the solid boron oxide layer and liquid boron oxide layer should be at least 50 [mu]m. 7 figs.

Self-Aligned Growth of Organic Semiconductor Single Crystals by Electric Field.

PubMed

Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro

2016-01-19

We proposed a novel but facile method for growing organic semiconductor single-crystals via solvent vapor annealing (SVA) under electric field. In the conventional SVA growth process, nuclei of crystals appeared anywhere on the substrate and their crystallographic axes were randomly distributed. We applied electric field during the SVA growth of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) on the SiO2/Si substrate on which a pair of electrodes had been deposited beforehand. Real-time observation of the SVA process revealed that rodlike single crystals grew with their long axes parallel to the electric field and bridged the prepatterned electrodes. As a result, C8-BTBT crystals automatically formed a field effect transistor (FET) structure and the mobility reached 1.9 cm(2)/(V s). Electric-field-assisted SVA proved a promising method for constructing high-mobility single-crystal FETs at the desired position by a low-cost solution process.

Crystal growth of device quality GaAs in space

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Lagowski, J.

1986-01-01

It was established that the findings on elemental semiconductors Ge and Si regarding crystal growth, segregation, chemical composition, defect interactions, and materials properties-electronic properties relationships are not necessarily applicable to GaAs (and to other semiconductor compounds). In many instances totally unexpected relationships were found to prevail. It was further established that in compound semiconductors with a volatile constituent, control of stoichiometry is far more critical than any other crystal growth parameter. It was also shown that, due to suppression of nonstoichiometric fluctuations, the advantages of space for growth of semiconductor compounds extend far beyond those observed in elemental semiconductors. A novel configuration was discovered for partial confinement of GaAs melt in space which overcomes the two major problems associated with growth of semiconductors in total confinement. They are volume expansion during solidification and control of pressure of the volatile constituent. These problems are discussed in detail.

Novel growth techniques of group-IV based semiconductors on insulator for next-generation electronics

NASA Astrophysics Data System (ADS)

Miyao, Masanobu; Sadoh, Taizoh

2017-05-01

Recent progress in the crystal growth of group-IV-based semiconductor-on-insulators is reviewed from physical and technological viewpoints. Liquid-phase growth based on SiGe-mixing-triggered rapid-melting growth enables formation of hybrid (100) (110) (111)-orientation Ge-on-insulator (GOI) structures, which show defect-free GOI with very high carrier mobility (˜1040 cm2 V-1 s-1). Additionally, SiGe mixed-crystals with laterally uniform composition were obtained by eliminating segregation phenomena during the melt-back process. Low-temperature solid-phase growth has been explored by combining this process with ion-beam irradiation, additional doping of group-IV elements, metal induced lateral crystallization with/without electric field, and metal-induced layer exchange crystallization. These efforts have enabled crystal growth on insulators below 400 °C, achieving high carrier mobility (160-320 cm2 V-1 s-1). Moreover, orientation-controlled SiGe and Ge films on insulators have been obtained below the softening temperatures of conventional plastic films (˜300 °C). Detailed characterization provides an understanding of physical phenomena behind these crystal growth techniques. Applying these methods when fabricating next-generation electronics is also discussed.

Overview of Characterization Techniques for High Speed Crystal Growth

NASA Technical Reports Server (NTRS)

Ravi, K. V.

1984-01-01

Features of characterization requirements for crystals, devices and completed products are discussed. Key parameters of interest in semiconductor processing are presented. Characterization as it applies to process control, diagnostics and research needs is discussed with appropriate examples.

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

PubMed Central

Vollebregt, Sten; Ishihara, Ryoichi

2015-01-01

We demonstrate a method for the low temperature growth (350 °C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-κ dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used. PMID:26709530

Cantilever epitaxial process

DOEpatents

Ashby, Carol I.; Follstaedt, David M.; Mitchell, Christine C.; Han, Jung

2003-07-29

A process of growing a material on a substrate, particularly growing a Group II-VI or Group III-V material, by a vapor-phase growth technique where the growth process eliminates the need for utilization of a mask or removal of the substrate from the reactor at any time during the processing. A nucleation layer is first grown upon which a middle layer is grown to provide surfaces for subsequent lateral cantilever growth. The lateral growth rate is controlled by altering the reactor temperature, pressure, reactant concentrations or reactant flow rates. Semiconductor materials, such as GaN, can be produced with dislocation densities less than 10.sup.7 /cm.sup.2.

GaN/NbN epitaxial semiconductor/superconductor heterostructures

NASA Astrophysics Data System (ADS)

Yan, Rusen; Khalsa, Guru; Vishwanath, Suresh; Han, Yimo; Wright, John; Rouvimov, Sergei; Katzer, D. Scott; Nepal, Neeraj; Downey, Brian P.; Muller, David A.; Xing, Huili G.; Meyer, David J.; Jena, Debdeep

2018-03-01

Epitaxy is a process by which a thin layer of one crystal is deposited in an ordered fashion onto a substrate crystal. The direct epitaxial growth of semiconductor heterostructures on top of crystalline superconductors has proved challenging. Here, however, we report the successful use of molecular beam epitaxy to grow and integrate niobium nitride (NbN)-based superconductors with the wide-bandgap family of semiconductors—silicon carbide, gallium nitride (GaN) and aluminium gallium nitride (AlGaN). We apply molecular beam epitaxy to grow an AlGaN/GaN quantum-well heterostructure directly on top of an ultrathin crystalline NbN superconductor. The resulting high-mobility, two-dimensional electron gas in the semiconductor exhibits quantum oscillations, and thus enables a semiconductor transistor—an electronic gain element—to be grown and fabricated directly on a crystalline superconductor. Using the epitaxial superconductor as the source load of the transistor, we observe in the transistor output characteristics a negative differential resistance—a feature often used in amplifiers and oscillators. Our demonstration of the direct epitaxial growth of high-quality semiconductor heterostructures and devices on crystalline nitride superconductors opens up the possibility of combining the macroscopic quantum effects of superconductors with the electronic, photonic and piezoelectric properties of the group III/nitride semiconductor family.

Materials for the Study of Interesting Phenomena of Solidification on Earth and in Orbit (MEPHISTO)

NASA Technical Reports Server (NTRS)

1987-01-01

The MEPHISTO experiment is a cooperative American and French investigation of the fundamentals of crystal growth. MEPHISTO is a French-designed and built materials processing furnace. MEPHISTO experiments study solidation (also called freezing) during the growth cycle of liquid materials used for semiconductor crystals. Solidification is the process where materials change from liquid (melt) to solid. An example of the solidification process is water changing into ice.

Research progress of Ge on insulator grown by rapid melting growth

NASA Astrophysics Data System (ADS)

Liu, Zhi; Wen, Juanjuan; Li, Chuanbo; Xue, Chunlai; Cheng, Buwen

2018-06-01

Ge is an attractive material for Si-based microelectronics and photonics due to its high carries mobility, pseudo direct bandgap structure, and the compatibility with complementary metal oxide semiconductor (CMOS) processes. Based on Ge, Ge on insulator (GOI) not only has these advantages, but also provides strong electronic and optical confinement. Recently, a novel technique to fabricate GOI by rapid melting growth (RMG) has been described. Here, we introduce the RMG technique and review recent efforts and progress in RMG. Firstly, we will introduce process steps of RMG. We will then review the researches which focus on characterizations of the GOI including growth dimension, growth mechanism, growth orientation, concentration distribution, and strain status. Finally, GOI based applications including high performance metal–oxide–semiconductor field effect transistors (MOSFETs) and photodetectors will be discussed. These results show that RMG is a promising technique for growth of high quality GOIs with different characterizations. The GOI grown by RMG is a potential material for the next-generation of integrated circuits and optoelectronic circuits. Project supported in part by the National Key Research and Development Program of China (No. 2017YFA0206404) and the National Natural Science Foundation of China (Nos. 61435013, 61534005, 61534004, 61604146).

Organic semiconductor growth and morphology considerations for organic thin-film transistors.

PubMed

Virkar, Ajay A; Mannsfeld, Stefan; Bao, Zhenan; Stingelin, Natalie

2010-09-08

Analogous to conventional inorganic semiconductors, the performance of organic semiconductors is directly related to their molecular packing, crystallinity, growth mode, and purity. In order to achieve the best possible performance, it is critical to understand how organic semiconductors nucleate and grow. Clever use of surface and dielectric modification chemistry can allow one to control the growth and morphology, which greatly influence the electrical properties of the organic transistor. In this Review, the nucleation and growth of organic semiconductors on dielectric surfaces is addressed. The first part of the Review concentrates on small-molecule organic semiconductors. The role of deposition conditions on film formation is described. The modification of the dielectric interface using polymers or self-assembled mono-layers and their effect on organic-semiconductor growth and performance is also discussed. The goal of this Review is primarily to discuss the thin-film formation of organic semiconducting species. The patterning of single crystals is discussed, while their nucleation and growth has been described elsewhere (see the Review by Liu et. al).([¹]) The second part of the Review focuses on polymeric semiconductors. The dependence of physico-chemical properties, such as chain length (i.e., molecular weight) of the constituting macromolecule, and the influence of small molecular species on, e.g., melting temperature, as well as routes to induce order in such macromolecules, are described.

Atomic layer deposition: an enabling technology for the growth of functional nanoscale semiconductors

NASA Astrophysics Data System (ADS)

Biyikli, Necmi; Haider, Ali

2017-09-01

In this paper, we present the progress in the growth of nanoscale semiconductors grown via atomic layer deposition (ALD). After the adoption by semiconductor chip industry, ALD became a widespread tool to grow functional films and conformal ultra-thin coatings for various applications. Based on self-limiting and ligand-exchange-based surface reactions, ALD enabled the low-temperature growth of nanoscale dielectric, metal, and semiconductor materials. Being able to deposit wafer-scale uniform semiconductor films at relatively low-temperatures, with sub-monolayer thickness control and ultimate conformality, makes ALD attractive for semiconductor device applications. Towards this end, precursors and low-temperature growth recipes are developed to deposit crystalline thin films for compound and elemental semiconductors. Conventional thermal ALD as well as plasma-assisted and radical-enhanced techniques have been exploited to achieve device-compatible film quality. Metal-oxides, III-nitrides, sulfides, and selenides are among the most popular semiconductor material families studied via ALD technology. Besides thin films, ALD can grow nanostructured semiconductors as well using either template-assisted growth methods or bottom-up controlled nucleation mechanisms. Among the demonstrated semiconductor nanostructures are nanoparticles, nano/quantum-dots, nanowires, nanotubes, nanofibers, nanopillars, hollow and core-shell versions of the afore-mentioned nanostructures, and 2D materials including transition metal dichalcogenides and graphene. ALD-grown nanoscale semiconductor materials find applications in a vast amount of applications including functional coatings, catalysis and photocatalysis, renewable energy conversion and storage, chemical sensing, opto-electronics, and flexible electronics. In this review, we give an overview of the current state-of-the-art in ALD-based nanoscale semiconductor research including the already demonstrated and future applications.

Semiconductor grade, solar silicon purification project

NASA Technical Reports Server (NTRS)

Ingle, W. M.; Rosler, R. R.; Thompson, S. W.; Chaney, R. E.

1979-01-01

Experimental apparatus and procedures used in the development of a 3-step SiF2(x) polymer transport purification process are described. Both S.S.M.S. and E.S. analysis demonstrated that major purification had occured and some samples were indistinguishable from semiconductor grade silicon (except possibly for phosphorus). Recent electrical analysis via crystal growth reveals that the product contains compensated phosphorus and boron. The low projected product cost and short energy payback time suggest that the economics of this process will result in a cost less than the goal of $10/Kg(1975 dollars). The process appears to be readily scalable to a major silicon purification facility.

Processing materials in space - The history and the future

NASA Technical Reports Server (NTRS)

Chassay, Roger; Carswell, Bill

1987-01-01

The development of materials processing in space, and some of the Soyuz, Apollo, Skylab, and Shuttle orbital materials experiments are reviewed. Consideration is given to protein crystal growth, electrophoresis, low-gravity isoelectric focusing, phase partitioning, a monodisperse latex reactor, semiconductor crystal growth, solution crystal growth, the triglycine sulfate experiment, vapor crystal growth experiments, the mercuric iodide experiment, electronic and electrooptical materials, organic thin films and crystalline solids, deep undercooling of metals and alloys, magnetic materials, immiscible materials, metal solidification research, reluctant glass-forming materials, and containerless glass formation. The space processing apparatuses and ground facilities, for materials processing are described. Future facilities for commercial research, development, and manufacturing in space are proposed.

CaTiO.sub.3 Interfacial template structure on semiconductor-based material and the growth of electroceramic thin-films in the perovskite class

DOEpatents

McKee, Rodney Allen; Walker, Frederick Joseph

1998-01-01

A structure including a film of a desired perovskite oxide which overlies and is fully commensurate with the material surface of a semiconductor-based substrate and an associated process for constructing the structure involves the build up of an interfacial template film of perovskite between the material surface and the desired perovskite film. The lattice parameters of the material surface and the perovskite of the template film are taken into account so that during the growth of the perovskite template film upon the material surface, the orientation of the perovskite of the template is rotated 45.degree. with respect to the orientation of the underlying material surface and thereby effects a transition in the lattice structure from fcc (of the semiconductor-based material) to the simple cubic lattice structure of perovskite while the fully commensurate periodicity between the perovskite template film and the underlying material surface is maintained. The film-growth techniques of the invention can be used to fabricate solid state electrical components wherein a perovskite film is built up upon a semiconductor-based material and the perovskite film is adapted to exhibit ferroelectric, piezoelectric, pyroelectric, electro-optic or large dielectric properties during use of the component.

Direct growth of single-crystalline III–V semiconductors on amorphous substrates

DOE PAGES

Chen, Kevin; Kapadia, Rehan; Harker, Audrey; ...

2016-01-27

The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V’s on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V’s of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. Themore » patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO 2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. In conclusion, the work presents an important advance towards universal integration of III–V’s on application-specific substrates by direct growth.« less

Direct growth of single-crystalline III–V semiconductors on amorphous substrates

PubMed Central

Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager III, Joel W.; Chrzan, Daryl C.; Javey, Ali

2016-01-01

The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III–V's on application-specific substrates by direct growth. PMID:26813257

X-Ray Diffraction (XRD) Characterization Methods for Sigma=3 Twin Defects in Cubic Semiconductor (100) Wafers

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); Kim, Hyun Jung (Inventor); Skuza, Jonathan R. (Inventor); Lee, Kunik (Inventor); Choi, Sang Hyouk (Inventor); King, Glen C. (Inventor)

2017-01-01

An X-ray defraction (XRD) characterization method for sigma=3 twin defects in cubic semiconductor (100) wafers includes a concentration measurement method and a wafer mapping method for any cubic tetrahedral semiconductor wafers including GaAs (100) wafers and Si (100) wafers. The methods use the cubic semiconductor's (004) pole figure in order to detect sigma=3/{111} twin defects. The XRD methods are applicable to any (100) wafers of tetrahedral cubic semiconductors in the diamond structure (Si, Ge, C) and cubic zinc-blend structure (InP, InGaAs, CdTe, ZnSe, and so on) with various growth methods such as Liquid Encapsulated Czochralski (LEC) growth, Molecular Beam Epitaxy (MBE), Organometallic Vapor Phase Epitaxy (OMVPE), Czochralski growth and Metal Organic Chemical Vapor Deposition (MOCVD) growth.

X-ray Characterization and Defect Control of III-Nitrides

NASA Astrophysics Data System (ADS)

Tweedie, James

A process for controlling point defects in a semiconductor using excess charge carriers was developed in theory and practice. A theoretical framework based on first principles was developed to model the effect of excess charge carriers on the formation energy and concentration of charged point defects in a semiconductor. The framework was validated for the completely general case of a generic carrier source and a generic point defect in a generic semiconductor, and then refined for the more specific case of a generic carrier source applied during the growth of a doped semiconductor crystal. It was theoretically demonstrated that the process as defined will always reduce the degree of compensation in the semiconductor. The established theoretical framework was applied to the case of above-bandgap illumination on both the MOCVD growth and the post-growth annealing of Mg-doped GaN thin films. It was theoretically demonstrated that UV light will lower the concentration of compensating defects during growth and will facilitate complete activation of the Mg acceptor at lower annealing temperatures. Annealing experiments demonstrated that UV illumination of GaN:Mg thin films during annealing lowers the resistivity of the film at any given temperature below the 650 °C threshold at which complete activation is achieved without illumination. Broad spectrum analysis of the photoluminescence (PL) spectra together with a correlation between the acceptor-bound exciton transition and room temperature resistivity demonstrated that UV light only acts to enhance the activation Mg. Surface chemistry and interface chemistry of AlN and high Al mole fraction AlGaN films were studied using x-ray photoelectron spectroscopy (XPS). It was seen that surfaces readily form stable surface oxides. The Schottky barrier height (SBH) of various metals contacted to these surfaces was using XPS. Finally, an x-ray diffraction method (XRD) was developed to quantify strain and composition of alloy films in the context of a processing environment. Reciprocal space mapping revealed intensity limitations on the accuracy of the method. The method was used to demonstrate a bimodal strain distribution across the composition spectrum for 200 nm AlGaN thin films grown on GaN. A weak, linear strain dependence on composition was observed for Al mole fractions below 30%. Above this threshold the films were observed to be completely relaxed by cracking.

Technological and organizational diversity and technical advance in the early history of the American semiconductor industry

NASA Astrophysics Data System (ADS)

Cohen, W.; Holbrook, D.; Klepper, S.

1994-06-01

This study examines the early years of the semiconductor industry and focuses on the roles played by different size firms in technologically innovative processes. A large and diverse pool of firms participated in the growth of the industry. Three related technological areas were chosen for in-depth analysis: integrated circuits, materials technology, and device packaging. Large business producing vacuum tubes dominated the early production of semiconductor devices. As the market for new devices grew during the 1950's, new firms were founded and existing firms from other industries, e.g. aircraft builders and instrument makers, began to pursue semiconductor electronics. Small firms began to cater to the emerging industry by supplying materials and equipment. These firms contributed to the development of certain aspects of one thousand firms that were playing some part in the semiconductor industry.

Facet-Selective Epitaxy of Compound Semiconductors on Faceted Silicon Nanowires.

PubMed

Mankin, Max N; Day, Robert W; Gao, Ruixuan; No, You-Shin; Kim, Sun-Kyung; McClelland, Arthur A; Bell, David C; Park, Hong-Gyu; Lieber, Charles M

2015-07-08

Integration of compound semiconductors with silicon (Si) has been a long-standing goal for the semiconductor industry, as direct band gap compound semiconductors offer, for example, attractive photonic properties not possible with Si devices. However, mismatches in lattice constant, thermal expansion coefficient, and polarity between Si and compound semiconductors render growth of epitaxial heterostructures challenging. Nanowires (NWs) are a promising platform for the integration of Si and compound semiconductors since their limited surface area can alleviate such material mismatch issues. Here, we demonstrate facet-selective growth of cadmium sulfide (CdS) on Si NWs. Aberration-corrected transmission electron microscopy analysis shows that crystalline CdS is grown epitaxially on the {111} and {110} surface facets of the Si NWs but that the Si{113} facets remain bare. Further analysis of CdS on Si NWs grown at higher deposition rates to yield a conformal shell reveals a thin oxide layer on the Si{113} facet. This observation and control experiments suggest that facet-selective growth is enabled by the formation of an oxide, which prevents subsequent shell growth on the Si{113} NW facets. Further studies of facet-selective epitaxial growth of CdS shells on micro-to-mesoscale wires, which allows tuning of the lateral width of the compound semiconductor layer without lithographic patterning, and InP shell growth on Si NWs demonstrate the generality of our growth technique. In addition, photoluminescence imaging and spectroscopy show that the epitaxial shells display strong and clean band edge emission, confirming their high photonic quality, and thus suggesting that facet-selective epitaxy on NW substrates represents a promising route to integration of compound semiconductors on Si.

Liquid phase electroepitaxial bulk growth of binary and ternary alloy semiconductors under external magnetic field

NASA Astrophysics Data System (ADS)

Sheibani, Hamdi

2002-01-01

Liquid Phase Electroepitaxy (LPEE) and is a relatively new, promising technique for producing high quality, thick compound semiconductors and their alloys. The main objectives are to reduce the adverse effect of natural convection and to determine the optimum growth conditions for reproducible desired crystals for the optoelectronic and electronic device industry. Among the available techniques for suppressing the adverse effect of natural convection, the application of an external magnetic field seems the most feasible one. The research work in this dissertation consists of two parts. The first part is focused on the design and development of a state of the art LPEE facility with a novel crucible design, that can produce bulk crystals of quality higher than those achieved by the existing LPEE system. A growth procedure was developed to take advantage of this novel crucible design. The research of the growth of InGaAs single crystals presented in this thesis will be a basis for the future LPEE growth of other important material and is an ideal vehicle for the development of a ternary crystal growth process. The second part of the research program is the experimental study of the LPEE growth process of high quality bulk single crystals of binary/ternary semiconductors under applied magnetic field. The compositional uniformity of grown crystals was measured by Electron Probe Micro-analysis (EPMA) and X-ray microanalysis. The state-of-the-art LPEE system developed at University of Victoria, because of its novel design features, has achieved a growth rate of about 4.5 mm/day (with the application of an external fixed magnetic field of 4.5 KGauss and 3 A/cm2 electric current density), and a growth rate of about 11 mm/day (with 4.5 KGauss magnetic field and 7 A/cm2 electric current density). This achievement is simply a breakthrough in LPEE, making this growth technique absolutely a bulk growth technique and putting it in competition with other bulk growth techniques. The growth rates achieved can even be higher for higher electric current and magnetic field intensities. (Abstract shortened by UMI.)

Removal of GaAs growth substrates from II-VI semiconductor heterostructures

NASA Astrophysics Data System (ADS)

Bieker, S.; Hartmann, P. R.; Kießling, T.; Rüth, M.; Schumacher, C.; Gould, C.; Ossau, W.; Molenkamp, L. W.

2014-04-01

We report on a process that enables the removal of II-VI semiconductor epilayers from their GaAs growth substrate and their subsequent transfer to arbitrary host environments. The technique combines mechanical lapping and layer selective chemical wet etching and is generally applicable to any II-VI layer stack. We demonstrate the non-invasiveness of the method by transferring an all-II-VI magnetic resonant tunneling diode. High resolution x-ray diffraction proves that the crystal integrity of the heterostructure is preserved. Transport characterization confirms that the functionality of the device is maintained and even improved, which is ascribed to completely elastic strain relaxation of the tunnel barrier layer.

Economic analysis of crystal growth in space

NASA Technical Reports Server (NTRS)

Ulrich, D. R.; Chung, A. M.; Yan, C. S.; Mccreight, L. R.

1972-01-01

Many advanced electronic technologies and devices for the 1980's are based on sophisticated compound single crystals, i.e. ceramic oxides and compound semiconductors. Space processing of these electronic crystals with maximum perfection, purity, and size is suggested. No ecomonic or technical justification was found for the growth of silicon single crystals for solid state electronic devices in space.

Semiconductor Laser Joint Study Program with Rome Laboratory

DTIC Science & Technology

1994-09-01

VCSELs 3.3 Laser Wafer Growth by Molecular Beam Epitaxy 8 The VCSEL structures were grown by molecular beam ...cavity surface emittimg lasers ( VCSEL ), Optical 40 interconnects, Moelcular beam epitaxy It CECOOE 17. SECURfTY CLASWICATION SECURFlY CLASSIFICATION 1 Q...7 3.3 Laser Wafer Growth by Molecular Beam Epitax. ............ 8 3.4 VCSEL Fabrication Process ................................................

Growth dynamics of SiGe nanowires by the vapour-liquid-solid method and its impact on SiGe/Si axial heterojunction abruptness.

PubMed

Pura, J L; Periwal, P; Baron, T; Jiménez, J

2018-08-31

The vapour-liquid-solid (VLS) method is by far the most extended procedure for bottom-up nanowire growth. This method also allows for the manufacture of nanowire axial heterojunctions in a straightforward way. To do this, during the growth process, precursor gases are switched on/off to obtain the desired change in the nanowire composition. Using this technique, axially heterostructured nanowires can be grown, which are crucial for the fabrication of electronic and optoelectronic devices. SiGe/Si nanowires are compatible with complementary metal oxide semiconductor (CMOS) technology, which improves their versatility and the possibility of integration with current electronic technologies. Abrupt heterointerfaces are fundamental for the development and correct operation of electronic and optoelectronic devices. Unfortunately, the VLS growth of SiGe/Si heterojunctions does not provide abrupt transitions because of the high solubility of group IV semiconductors in Au, with the corresponding reservoir effect that precludes the growth of sharp interfaces. In this work, we studied the growth dynamics of SiGe/Si heterojunctions based on already developed models for VLS growth. A composition map of the Si-Ge-Au liquid alloy is proposed to better understand the impact of the growing conditions on the nanowire growth process and the heterojunction formation. The solution of our model provides heterojunction profiles that are in good agreement with the experimental measurements. Finally, an in-depth study of the composition map provides a practical approach to the drastic reduction of heterojunction abruptness by reducing the Si and Ge concentrations in the catalyst droplet. This converges with previous approaches, which use catalysts aiming to reduce the solubility of the atomic species. This analysis opens new paths to the reduction of heterojunction abruptness using Au catalysts, but the model can be naturally extended to other catalysts and semiconductors.

Effect of molecular asymmetry on the charge transport physics of high mobility n-type molecular semiconductors investigated by scanning Kelvin probe microscopy.

PubMed

Hu, Yuanyuan; Berdunov, Nikolai; Di, Chong-an; Nandhakumar, Iris; Zhang, Fengjiao; Gao, Xike; Zhu, Daoben; Sirringhaus, Henning

2014-07-22

We have investigated the influence of the symmetry of the side chain substituents in high-mobility, solution processable n-type molecular semiconductors on the performance of organic field-effect transistors (OFETs). We compare two molecules with the same conjugated core, but either symmetric or asymmetric side chain substituents, and investigate the transport properties and thin film growth mode using scanning Kelvin probe microscopy (SKPM) and atomic force microscopy (AFM). We find that asymmetric side chains can induce a favorable two-dimensional growth mode with a bilayer structure, which enables ultrathin films with a single bilayer to exhibit excellent transport properties, while the symmetric molecules adopt an unfavorable three-dimensional growth mode in which transport in the first monolayer at the interface is severely hindered by high-resistance grain boundaries.

Monolayer-Mediated Growth of Organic Semiconductor Films with Improved Device Performance.

PubMed

Huang, Lizhen; Hu, Xiaorong; Chi, Lifeng

2015-09-15

Increased interest in wearable and smart electronics is driving numerous research works on organic electronics. The control of film growth and patterning is of great importance when targeting high-performance organic semiconductor devices. In this Feature Article, we summarize our recent work focusing on the growth, crystallization, and device operation of organic semiconductors intermediated by ultrathin organic films (in most cases, only a monolayer). The site-selective growth, modified crystallization and morphology, and improved device performance of organic semiconductor films are demonstrated with the help of the inducing layers, including patterned and uniform Langmuir-Blodgett monolayers, crystalline ultrathin organic films, and self-assembled polymer brush films. The introduction of the inducing layers could dramatically change the diffusion of the organic semiconductors on the surface and the interactions between the active layer with the inducing layer, leading to improved aggregation/crystallization behavior and device performance.

Crystal Growth by Physical Vapor Transport: Experiments and Simulation Dynamics

NASA Technical Reports Server (NTRS)

Ramachandran, N.; Worlikar, A.; Su, Ching-Hua; Rose, M. Franklin (Technical Monitor)

2001-01-01

Crystal growth from the vapor phase has various advantages over melt growth. The main advantage is from a lower processing temperature, which makes the process more amenable in instances where the melting temperature of the crystal is high. Other benefits stem from the inherent purification mechanism in the process due to differences in the vapor pressures of the native elements and impurities, and the enhanced interfacial morphological stability during the growth process. Further, the implementation of PVT growth in closed ampoules affords experimental simplicity with minimal needs for complex process control, which makes it an ideal candidate for space investigations in systems where gravity tends to have undesirable effects on the growth process. Bulk growth of wide band gap II-VI semiconductors by PVT has been developed and refined over the past several years at NASA MSFC. A new modeling approach for PVT has also been recently formulated and its validation and testing is the main objective of this work.

Selective growth of n-type nanoparticles on p-type semiconductors for Z-scheme photocatalysis.

PubMed

Miyauchi, Masahiro; Nukui, Yuuya; Atarashi, Daiki; Sakai, Etsuo

2013-10-09

Nanoparticles of an n-type WO3 semiconductor were segregated on the surface of p-type CaFe2O4 particles by a heterogeneous nucleation process under controlled hydrothermal conditions. By use of this approach, WO3 nanoparticles were selectively deposited on the surface of CaFe2O4, resulting in a significant increase in the photocatalytic reaction rate of the WO3/CaFe2O4 composite for the decomposition of gaseous acetaldehyde under visible-light irradiation. The high visible-light activity of the WO3/CaFe2O4 composite was due to efficient charge recombination through the junctions that formed between the two semiconductors.

Advanced 3-V semiconductor technology assessment

NASA Technical Reports Server (NTRS)

Nowogrodzki, M.

1983-01-01

Components required for extensions of currently planned space communications systems are discussed for large antennas, crosslink systems, single sideband systems, Aerostat systems, and digital signal processing. Systems using advanced modulation concepts and new concepts in communications satellites are included. The current status and trends in materials technology are examined with emphasis on bulk growth of semi-insulating GaAs and InP, epitaxial growth, and ion implantation. Microwave solid state discrete active devices, multigigabit rate GaAs digital integrated circuits, microwave integrated circuits, and the exploratory development of GaInAs devices, heterojunction devices, and quasi-ballistic devices is considered. Competing technologies such as RF power generation, filter structures, and microwave circuit fabrication are discussed. The fundamental limits of semiconductor devices and problems in implementation are explored.

Growth and device processing of hexagonal boron nitride epilayers for thermal neutron and deep ultraviolet detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doan, T. C.; Li, J.; Lin, J. Y.

2016-07-15

Solid-state neutron detectors with high performance are highly sought after for the detection of fissile materials. However, direct-conversion neutron detectors based on semiconductors with a measureable efficiency have not been realized. We report here the first successful demonstration of a direct-conversion semiconductor neutron detector with an overall detection efficiency for thermal neutrons of 4% and a charge collection efficiency as high as 83%. The detector is based on a 2.7 μm thick {sup 10}B-enriched hexagonal boron nitride (h-BN) epitaxial layer. The results represent a significant step towards the realization of practical neutron detectors based on h-BN epilayers. Neutron detectors basedmore » on h-BN are expected to possess all the advantages of semiconductor devices including wafer-scale processing, compact size, light weight, and ability to integrate with other functional devices.« less

Crystal growth of device quality GaAs in space

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Lagowski, J.

1984-01-01

The crystal growth, device processing and device related properties and phenomena of GaAs are investigated. Our GaAs research evolves about these key thrust areas. The overall program combines: (1) studies of crystal growth on novel approaches to engineering of semiconductor materials (i.e., GaAs and related compounds); (2) investigation and correlation of materials properties and electronic characteristics on a macro- and microscale; (3) investigation of electronic properties and phenomena controlling device applications and device performance. The ground based program is developed which would insure successful experimentation with and eventually processing of GaAs in a near zero gravity environment.

Insights Into the Solution Crystallization of Oriented Alq3 and Znq2 Microprisms and Nanorods.

PubMed

Boulet, Joel; Mohammadpour, Arash; Shankar, Karthik

2015-09-01

Optimized solution-based methods to grow high quality micro- and nanocrystals of organic semi-conductors with defined size, shape and orientation are important to a variety of optoelectronic applications. In this context, we report the growth of single crystal micro- and nanostructures of the organic semiconductors Tris(8-hydroxyquinoline)aluminum (Alq3) and bis(8-hydroxyquinoline)zinc (Znq2) terminating in flat crystal planes using a combination of evaporative and antisolvent crystallization. By controlling substrate-specific nucleation and optimizing the conditions of growth, we generate vertically-oriented hexagonal prism arrays of Alq3, and vertical half-disks and sharp-edged rectangular prisms of Znq2. The effect of process variables such as ambient vapour pressure, choice of anti-solvent and temperature on the morphology and crystal habit of the nanostructures were studied and the results of varying them catalogued to gain a better understanding of the mechanism of growth.

Investigation of temperature and concentration oscillations in the directional solidification of Pb-Sn-Te

NASA Technical Reports Server (NTRS)

Anderson, T. J.; Narayanan, R.

1987-01-01

Directional solidification of the pseudobinary compound semiconductor material Pb sub 1-x Sn sub x Te by the Bridgman crystal growth process will be studied. Natural convection in the molten sample will be visualized with a novel electrochemical cell technique that employs the solid electrolyte material yttria-stabilized zirconia. Mass transfer by both diffusion and convection will be measured by detecting the motion of oxygen tracer in the liquid. Additional applications for electrochemical cells in semiconductor crystal growth are suggested. Unsteady convection in the melt will also be detected by the appearance of temperature oscillations. The purpose of this study is to experimentally characterize the overstable conditions for a Pb sub 1-x Sn sub x Te melt in the vertical Bridgman crystal growth technique and use a linear analysis to predict the onset of convection for this system.

Material growth and characterization for solid state devices

NASA Technical Reports Server (NTRS)

Collis, Ward J.; Abul-Fadl, Ali; Iyer, Shanthi

1988-01-01

During the period of this research grant, the process of liquid phase electroepitaxy (LPEE) was used to grow ternary and quaternary alloy III-V semiconductor thin films. Selective area growth of InGaAs was performed on InP substrates using a patterned sputtered quartz or spin-on glass layer. The etch back and growth characteristics with respect to substrate orientation were investigated. The etch back behavior is somewhat different from wet chemical etching with respect to the sidewall profiles which are observed. LPEE was also employed to grow epitaxial layers of InGaAsP alloys on InP substrates. The behavior of Mn as an acceptor dopant was investigated with low temperature Hall coefficient and photoluminescence measurements. A metal-organic vapor phase epitaxy system was partially complete within the grant period. This atmospheric pressure system will be used to deposit III-V compound and alloy semiconductor layers in future research efforts.

Astronaut Peggy Whitson Installs SUBSA Experiment

NASA Technical Reports Server (NTRS)

2002-01-01

Expedition Five flight engineer Peggy Whitson is shown installing the Solidification Using a Baffle in Sealed Ampoules (SUBSA) experiment in the Microgravity Science Glovebox (MSG) in the Destiny laboratory aboard the International Space Station (ISS). SUBSA examines the solidification of semiconductor crystals from a melted material. Semiconductor crystals are used for many products that touch our everyday lives. They are found in computer chips, integrated circuits, and a multitude of other electronic devices, such as sensors for medical imaging equipment and detectors of nuclear radiation. Materials scientists want to make better semiconductor crystals to be able to further reduce the size of high-tech devices. In the microgravity environment, convection and sedimentation are reduced, so fluids do not remove and deform. Thus, space laboratories provide an ideal environment of studying solidification from the melt. This investigation is expected to determine the mechanism causing fluid motion during production of semiconductors in space. It will provide insight into the role of the melt motion in production of semiconductor crystals, advancing our knowledge of the crystal growth process. This could lead to a reduction of defects in semiconductor crystals produced in space and on Earth.

International Space Station (ISS)

NASA Image and Video Library

2002-07-05

Expedition Five flight engineer Peggy Whitson is shown installing the Solidification Using a Baffle in Sealed Ampoules (SUBSA) experiment in the Microgravity Science Glovebox (MSG) in the Destiny laboratory aboard the International Space Station (ISS). SUBSA examines the solidification of semiconductor crystals from a melted material. Semiconductor crystals are used for many products that touch our everyday lives. They are found in computer chips, integrated circuits, and a multitude of other electronic devices, such as sensors for medical imaging equipment and detectors of nuclear radiation. Materials scientists want to make better semiconductor crystals to be able to further reduce the size of high-tech devices. In the microgravity environment, convection and sedimentation are reduced, so fluids do not remove and deform. Thus, space laboratories provide an ideal environment of studying solidification from the melt. This investigation is expected to determine the mechanism causing fluid motion during production of semiconductors in space. It will provide insight into the role of the melt motion in production of semiconductor crystals, advancing our knowledge of the crystal growth process. This could lead to a reduction of defects in semiconductor crystals produced in space and on Earth.

Simulations of Quantum Dot Growth on Semiconductor Surfaces: Morphological Design of Sensor Concepts

DTIC Science & Technology

2008-12-01

size equalization can be clearly illustrated during the growth process. In this work we develop a fast multiscale 3D kinetic Monte Carlo ( KMC ) QD...model will provide an attractive means for producing predictably ordered nanostructures. MODEL DESCRIPTION The 3D layer-by-layer KMC growth model...Voter, 2001) and KMC simulation experience (Pan et al., 2004; Pan et al., 2006; Meixner et al, 2003) in 2D, we therefore propose the following simple

Lattice-Matched Semiconductor Layers on Single Crystalline Sapphire Substrate

NASA Technical Reports Server (NTRS)

Choi, Sang; King, Glen; Park, Yeonjoon

2009-01-01

SiGe is an important semiconductor alloy for high-speed field effect transistors (FETs), high-temperature thermoelectric devices, photovoltaic solar cells, and photon detectors. The growth of SiGe layer is difficult because SiGe alloys have different lattice constants from those of the common Si wafers, which leads to a high density of defects, including dislocations, micro-twins, cracks, and delaminations. This innovation utilizes newly developed rhombohedral epitaxy of cubic semiconductors on trigonal substrates in order to solve the lattice mismatch problem of SiGe by using trigonal single crystals like sapphire (Al2O3) as substrate to give a unique growth-orientation to the SiGe layer, which is automatically controlled at the interface upon sapphire (0001). This technology is different from previous silicon on insulator (SOI) or SGOI (SiGe on insulator) technologies that use amorphous SiO2 as the growth plane. A cubic semiconductor crystal is a special case of a rhombohedron with the inter-planar angle, alpha = 90 deg. With a mathematical transformation, all rhombohedrons can be described by trigonal crystal lattice structures. Therefore, all cubic lattice constants and crystal planes (hkl) s can be transformed into those of trigonal crystal parameters. These unique alignments enable a new opportunity of perfect lattice matching conditions, which can eliminate misfit dislocations. Previously, these atomic alignments were thought to be impossible or very difficult. With the invention of a new x-ray diffraction measurement method here, growth of cubic semiconductors on trigonal crystals became possible. This epitaxy and lattice-matching condition can be applied not only to SiGe (111)/sapphire (0001) substrate relations, but also to other crystal structures and other materials, including similar crystal structures which have pointgroup rotational symmetries by 120 because the cubic (111) direction has 120 rotational symmetry. The use of slightly miscut (less than plus or minus 10 deg.) sapphire (0001) substrate can be used to improve epitaxial relationships better by providing attractive atomic steps in the epitaxial process.

Nanoscale-driven crystal growth of hexaferrite heterostructures for magnetoelectric tuning of microwave semiconductor integrated devices.

PubMed

Hu, Bolin; Chen, Zhaohui; Su, Zhijuan; Wang, Xian; Daigle, Andrew; Andalib, Parisa; Wolf, Jason; McHenry, Michael E; Chen, Yajie; Harris, Vincent G

2014-11-25

A nanoscale-driven crystal growth of magnetic hexaferrites was successfully demonstrated at low growth temperatures (25-40% lower than the temperatures required often for crystal growth). This outcome exhibits thermodynamic processes of crystal growth, allowing ease in fabrication of advanced multifunctional materials. Most importantly, the crystal growth technique is considered theoretically and experimentally to be universal and suitable for the growth of a wide range of diverse crystals. In the present experiment, the conical spin structure of Co2Y ferrite crystals was found to give rise to an intrinsic magnetoelectric effect. Our experiment reveals a remarkable increase in the conical phase transition temperature by ∼150 K for Co2Y ferrite, compared to 5-10 K of Zn2Y ferrites recently reported. The high quality Co2Y ferrite crystals, having low microwave loss and magnetoelectricity, were successfully grown on a wide bandgap semiconductor GaN. The demonstration of the nanostructure materials-based "system on a wafer" architecture is a critical milestone to next generation microwave integrated systems. It is also practical that future microwave integrated systems and their magnetic performances could be tuned by an electric field because of the magnetoelectricity of hexaferrites.

Survey Analysis of Materials Processing Experiments Aboard STS-47: Spacelab J

NASA Technical Reports Server (NTRS)

Sharpe, R. J.; Wright, M. D.

2009-01-01

This Technical Memorandum (TM) is a survey outline of materials processing experiments aboard Space Shuttle Mission STS-47: Spacelab J, a joint venture between NASA and the National Space Development Agency of Japan. The mission explored materials processing experiments including electronics and crystal growth materials, metals and alloys, glasses and ceramics, and fluids. Experiments covered include Growth of Silicone Spherical Crystals and Surface Oxidation, Growth Experiment of Narrow Band-Gap Semiconductor Lead-Tin-Tellurium Crystals in Space, Study on Solidification of Immiscible Alloys, Fabrication of Very-Low-Density, High-Stiffness Carbon Fiber/Aluminum Hybridized Composites, High Temperature Behavior of Glass, and Study of Bubble Behavior. The TM underscores the historical significance of these experiments in the context of materials processing in space.

Organizational Growth: Linking Founding Team, Strategy, Environment, and Growth among U.S. Semiconductor Ventures, 1978-1988.

ERIC Educational Resources Information Center

Eisenhardt, Kathleen M.; Schoonhoven, Claudia Bird

1990-01-01

Summarizes a study exploring organizational growth in technology-based ventures. Characteristics of the founding top-management team, strategy, and environment are matched to the sales growth of newly founded semiconductor firms. Results show that the effects of the founding team and environment grew instead of fading with time. Includes 54…

Thermal Diffusivity for III-VI Semiconductor Melts at Different Temperatures

NASA Technical Reports Server (NTRS)

Ban, H.; Li, C.; Lin, B.; Emoto, K.; Scripa, R. N.; Su, C.-H.; Lehoczky, S. L.

2004-01-01

The change of the thermal properties of semiconductor melts reflects the structural changes inside the melts, and a fundamental understanding of this structural transformation is essential for high quality semiconductor crystal growth process. This paper focused on the technical development and the measurement of thermal properties of III-VI semiconductor melts at high temperatures. Our previous work has improved the laser flash method for the specialized quartz sample cell. In this paper, we reported the results of our recent progress in further improvements of the measurement system by minimizing the free convection of the melt, adding a front IR detector, and placing the sample cell in a vacuum environment. The results for tellurium and selenium based compounds, some of which have never been reported in the literature, were obtained at different temperatures as a function of time. The data were compared with other measured thermophysical properties to shed light on the structural transformations of the melt.

Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Burger, Arnold; Dudley, Michael; Matyi, Richard J.; Ramachandran, Narayanan; Sha, Yi-Gao; Volz, Martin; Shih, Hung-Dah

1998-01-01

Interest in optical devices which can operate in the visible spectrum has motivated research interest in the II-VI wide band gap semiconductor materials. The recent challenge for semiconductor opto-electronics is the development of a laser which can operate at short visible wavelengths, In the past several years, major advances in thin film technology such as molecular beam epitaxy and metal organic chemical vapor deposition have demonstrated the applicability of II-VI materials to important devices such as light-emitting diodes, lasers, and ultraviolet detectors.The demonstration of its optical bistable properties in bulk and thin film forms also make ZnSe a possible candidate material for the building blocks of a digital optical computer. Despite this, developments in the crystal growth of bulk II-VI semiconductor materials has not advanced far enough to provide the low price, high quality substrates needed for the thin film growth technology. The electrical and optical properties of semiconductor materials depend on the native point defects, (the deviation from stoichiometry), and the impurity or dopant distribution. To date, the bulk growth of ZnSe substrates has been plagued with problems related to defects such as non-uniform distributions of native defects, impurities and dopants, lattice strain, dislocations, grain boundaries, and second phase inclusions which greatly effect the device performance. In the bulk crystal growth of some technologically important semiconductors, such as ZnTe, CdS, ZnSe and ZnS, vapor growth techniques have significant advantages over melt growth techniques due to the high melting points of these materials.

Silicon carbide, a semiconductor for space power electronics

NASA Technical Reports Server (NTRS)

Powell, J. Anthony; Matus, Lawrence G.

1991-01-01

After many years of promise as a high temperature semiconductor, silicon carbide (SiC) is finally emerging as a useful electronic material. Recent significant progress that has led to this emergence has been in the areas of crystal growth and device fabrication technology. High quality single-crystal SiC wafers, up to 25 mm in diameter, can now be produced routinely from boules grown by a high temperature (2700 K) sublimation process. Device fabrication processes, including chemical vapor deposition (CVD), in situ doping during CVD, reactive ion etching, oxidation, metallization, etc. have been used to fabricate p-n junction diodes and MOSFETs. The diode was operated to 870 K and the MOSFET to 770 K.

Electrochemical liquid-liquid-solid (ec-LLS) crystal growth: a low-temperature strategy for covalent semiconductor crystal growth.

PubMed

Fahrenkrug, Eli; Maldonado, Stephen

2015-07-21

This Account describes a new electrochemical synthetic strategy for direct growth of crystalline covalent group IV and III-V semiconductor materials at or near ambient temperature conditions. This strategy, which we call "electrochemical liquid-liquid-solid" (ec-LLS) crystal growth, marries the semiconductor solvation properties of liquid metal melts with the utility and simplicity of conventional electrodeposition. A low-temperature liquid metal (i.e., Hg, Ga, or alloy thereof) acts simultaneously as the source of electrons for the heterogeneous reduction of oxidized semiconductor precursors dissolved in an electrolyte as well as the solvent for dissolution of the zero-valent semiconductor. Supersaturation of the semiconductor in the liquid metal triggers eventual crystal nucleation and growth. In this way, the liquid electrolyte-liquid metal-solid crystal phase boundary strongly influences crystal growth. As a synthetic strategy, ec-LLS has several intrinsic features that are attractive for preparing covalent semiconductor crystals. First, ec-LLS does not require high temperatures, toxic precursors, or high-energy-density semiconductor reagents. This largely simplifies equipment complexity and expense. In practice, ec-LLS can be performed with only a beaker filled with electrolyte and an electrical circuit capable of supplying a defined current (e.g., a battery in series with a resistor). By this same token, ec-LLS is compatible with thermally and chemically sensitive substrates (e.g., plastics) that cannot be used as deposition substrates in conventional syntheses of covalent semiconductors. Second, ec-LLS affords control over a host of crystal shapes and sizes through simple changes in common experimental parameters. As described in detail herein, large and small semiconductor crystals can be grown both homogeneously within a liquid metal electrode and heterogeneously at the interface of a liquid metal electrode and a seed substrate, depending on the particular details chosen for ec-LLS. Third, the rate of introduction of zero-valent materials into the liquid metal is precisely gated with a high degree of resolution by the applied potential/current. The intent of this Account is to summarize the key elements of ec-LLS identified to date, first contextualizing this method with respect to other semiconductor crystal growth methods and then highlighting some unique capabilities of ec-LLS. Specifically, we detail ec-LLS as a platform to prepare Ge and Si crystals from bulk- (∼1 cm(3)), micro- (∼10(-10) cm(3)), and nano-sized (∼10(-16) cm(3)) liquid metal electrodes in common solvents at low temperature. In addition, we describe our successes in the preparation of more compositionally complex binary covalent III-V semiconductors.

High density group IV semiconductor nanowire arrays fabricated in nanoporous alumina templates

NASA Astrophysics Data System (ADS)

Redwing, Joan M.; Dilts, Sarah M.; Lew, Kok-Keong; Cranmer, Alexana E.; Mohney, Suzanne E.

2005-11-01

The fabrication of high density arrays of semiconductor nanowires is of interest for nanoscale electronics, chemical and biological sensing and energy conversion applications. We have investigated the synthesis, intentional doping and electrical characterization of Si and Ge nanowires grown by the vapor-liquid-solid (VLS) method in nanoporous alumina membranes. Nanoporous membranes provide a convenient platform for nanowire growth and processing, enabling control of wire diameter via pore size and the integration of contact metals for electrical testing. For VLS growth in nanoporous materials, reduced pressures and temperatures are required in order to promote the diffusion of reactants into the pore without premature decomposition on the membrane surface or pore walls. The effect of growth conditions on the growth rate of Si and Ge nanowires from SiH 4 and GeH 4 sources, respectively, was investigated and compared. In both cases, the measured activation energies for nanowire growth were substantially lower than activation energies typically reported for Si and Ge thin film deposition under similar growth conditions, suggesting that gold plays a catalytic role in the VLS growth process. Intentionally doped SiNW arrays were also prepared using trimethylboron (TMB) and phosphine (PH 3) as p-type and n-type dopant sources, respectively. Nanowire resistivities were calculated from plots of the array resistance as a function of nanowire length. A decrease in resistivity was observed for both n-type and p-type doped SiNW arrays compared to those grown without the addition of a dopant source.

Progress in silicon carbide semiconductor technology

NASA Technical Reports Server (NTRS)

Powell, J. A.; Neudeck, P. G.; Matus, L. G.; Petit, J. B.

1992-01-01

Silicon carbide semiconductor technology has been advancing rapidly over the last several years. Advances have been made in boule growth, thin film growth, and device fabrication. This paper wi11 review reasons for the renewed interest in SiC, and will review recent developments in both crystal growth and device fabrication.

Numerical simulations of epitaxial growth process in MOVPE reactor as a tool for design of modern semiconductors for high power electronics

NASA Astrophysics Data System (ADS)

Skibinski, Jakub; Caban, Piotr; Wejrzanowski, Tomasz; Kurzydlowski, Krzysztof J.

2014-10-01

In the present study numerical simulations of epitaxial growth of gallium nitride in Metal Organic Vapor Phase Epitaxy reactor AIX-200/4RF-S is addressed. Epitaxial growth means crystal growth that progresses while inheriting the laminar structure and the orientation of substrate crystals. One of the technological problems is to obtain homogeneous growth rate over the main deposit area. Since there are many agents influencing reaction on crystal area such as temperature, pressure, gas flow or reactor geometry, it is difficult to design optimal process. According to the fact that it's impossible to determine experimentally the exact distribution of heat and mass transfer inside the reactor during crystal growth, modeling is the only solution to understand the process precisely. Numerical simulations allow to understand the epitaxial process by calculation of heat and mass transfer distribution during growth of gallium nitride. Including chemical reactions in numerical model allows to calculate the growth rate of the substrate and estimate the optimal process conditions for obtaining the most homogeneous product.

Semiconductor crystal growth and segregation problems on earth and in space

NASA Technical Reports Server (NTRS)

Gatos, H. C.

1982-01-01

Semiconductor crystal growth and segregation problems are examined in the context of their relationship to material properties, and some of the problems are illustrated with specific experimental results. The compositional and structural defects encountered in semiconductors are largely associated with gravity-induced convective currents in the melt; additional problems are introduced by variations in stoichiometry. It is demonstrated that in near-zero gravity environment, crystal growth and segregation takes place under ideal steady-state conditions with minimum convective interference. A discussion of the advantages of zero-gravity crystal growth is followed by a summary of problems arising from the absence of gravitational forces.

Initial formation behaviour of polypyrrole on single crystal TiO2 through photo-electrochemical reaction.

PubMed

Kawakita, Jin; Weitzel, Matthias

2011-04-01

Hybrid materials of the organic and inorganic semiconductors have a potential to show the better performance in the charge separation at the junction upon the photovoltaic action by the presence of the space charge layer in the inorganic semiconductor. In this study, the photo-anodic polymerization was selected as a fabrication method for the hybrid materials composed of TiO2 and polypyrrole on the basis of some advantages of this method. For the process control of the photo-anodic polymerization, it is important to elucidate the formation and growth mechanisms of the organic polymer. In this study, a flat sheet of single-crystal TiO2 was used as a well-defined surface for preparation of the organic polymer of pyrrole. Photo-anodic polarization behaviour was clarified and polypyrrole was prepared on TiO2. The formation process, especially the initial step was revealed by observation of polypyrrole with atomic force microscope (AFM) and statistical interpretation of the morphology of polypyrrole in the nano-scopic level. The formation process of polypyrrole on the TiO2 surface was summarized; (1) adsorption of precursors, (2) localized formation and growth of polypyrrole under the photo-illumination, and (3) homogenous growth of polypyrrole with the external current application under the photo-illumination.

Program Solicitation Number 86.1, Small Business Innovation Research Program.

DTIC Science & Technology

1986-01-31

Temperature Heat Pipe Technology DESCRIPTION: Heat pipes have been shown to provide superior growth conditions for the growth of bulk semiconductor crystals... Heat pipes allow for the establishment of isothermal conditions over large areas. This thermal property controls the distribution of impurities, and...reliable high temperature heat pipes to operate at 1325 degrees C with inert overpressures of 60 atmospheres is required for the processing of III-V

Thermally controlled growth of surface nanostructures on ion-modified AIII-BV semiconductor crystals

NASA Astrophysics Data System (ADS)

Trynkiewicz, Elzbieta; Jany, Benedykt R.; Wrana, Dominik; Krok, Franciszek

2018-01-01

The primary motivation for our systematic study is to provide a comprehensive overview of the role of sample temperature on the pattern evolution of several AIII-BV semiconductor crystal (001) surfaces (i.e., InSb, InP, InAs, GaSb) in terms of their response to low-energy Ar+ ion irradiation conditions. The surface morphology and the chemical diversity of such ion-modified binary materials has been characterized by means of scanning electron microscopy (SEM). In general, all surface textures following ion irradiation exhibit transitional behavior from small islands, via vertically oriented 3D nanostructures, to smoothened surface when the sample temperature is increased. This result reinforces our conviction that the mass redistribution of adatoms along the surface plays a vital role during the formation and growth process of surface nanostructures. We would like to emphasize that this paper addresses in detail for the first time the topic of the growth kinetics of the nanostructures with regard to thermal surface diffusion, while simultaneously offering some possible approaches to supplementing previous studies and therein gaining a new insight into this complex issue. The experimental results are discussed with reference to models of the pillars growth, abutting on preferential sputtering, the self-sustained etch masking effect and the redeposition process recently proposed to elucidate the observed nanostructuring mechanism.

Molecular organic crystalline matrix for hybrid organic-inorganic (nano) composite materials

NASA Astrophysics Data System (ADS)

Stanculescu, A.; Tugulea, L.; Alexandru, H. V.; Stanculescu, F.; Socol, M.

2005-02-01

Metal-doped benzil crystals have been grown by thermal gradient solidification in a vertical transparent growth configuration to investigate the effect of metallic guest on the ordered organic host. We have identified the conditions for growing homogeneous, optically good crystals of benzil doped with sodium and silver, limiting the effect of supercooling, low thermal conductivity and anisotropy of the growth speed (temperature gradient at the liquid-solid interface: 10-25 °C, moving speed of the growth interface 2.0 mm/h). The nature and concentration of the dopant are parameters affecting, through the growth process, the crystalline perfection and the optical properties of the organic matrix. Bulk optical characterisation, by spectrophotometrical methods, has offered details on some intrinsic properties of the system metal particles/benzil crystalline matrix. Analytical processing of the experimental data emphasised that benzil is a wide optical band gap organic semiconductor Eg=2.65 eV. We also have investigated the effect of sodium and silver on the properties of benzil crystal as potential transparent semiconductor matrix for (nano)composite metal/molecular organic material. With the increase of sodium concentration from c=1 to 6 wt%, a small narrowing of the band gap has been remarked. The same behaviour has been found for benzil doped with silver (c=2 wt%) compared to pure benzil.

Partially confined configuration for the growth of semiconductor crystals from the melt in zero-gravity environment

NASA Technical Reports Server (NTRS)

Lagowski, J.; Gatos, H. C.; Dabkowski, F. P.

1985-01-01

A novel partially confined configuration is proposed for the crystal growth of semiconductors from the melt, including those with volatile constituents. A triangular prism is employed to contain the growth melt. Due to surface tension, the melt will acquire a cylindrical-like shape and thus contact the prism along three parallel lines. The three empty spaces between the cylindrical melt and the edges of the prism will accommodate the expansion of the solidifying semiconductor, and in the case of semiconductor compounds with a volatile constituent, will permit the presence of the desired vapor phase in contact with the melt for controlling the melt stoichiometry. Theoretical and experimental evidence in support of this new type of confinement is presented.

Growth of Compound Semiconductors in a Low Gravity Environment: Microgravity Growth of PbSnTe

NASA Technical Reports Server (NTRS)

Fripp, Archibald L.; Debnam, William J.; Rosch, William R.; Baker, N. R.; Narayanan, R.

1999-01-01

The growth of the alloy compound semiconductor lead tin telluride (PbSnTe) was chosen for a microgravity flight experiment in the Advanced Automated Directional Solidification Furnace (AADSF), on the United States Microgravity Payload-3 (USMP-3) and on USMP-4 Space Shuttle flights in February, 1996, and November, 1997. The objective of these experiments was to determine the effect of the reduction in convection, during the growth process, brought about by the microgravity environment. The properties of devices made from PbSnTe are dependent on the ratio of the elemental components in the starting crystal. Compositional uniformity in the crystal is only obtained if there is no significant mixing in the liquid during growth. Lead tin telluride is an alloy of PbTe and SnTe. The technological importance of PbSnTe lies in its band gap versus composition diagram which has a zero energy crossing at approximately 40% SnTe. This facilitates the construction of long wavelength (>6 micron) infrared detectors and lasers. Observations and experimental methods of crystal growth of PbSnTe on both Space Shuttle Flights are presented.

John Simon | NREL

Science.gov Websites

novel crystalline substrates for growth of III-V Nitride semiconductors for solid-state lighting applications. Since then he has been involved in various projects involving the growth of III-V semiconductor .; Romero, M.; and Lee, M.J. "Metamorphic GaAsP buffers for growth of wide-bandgap InGaP solar cells

Highly Crystalline C8-BTBT Thin-Film Transistors by Lateral Homo-Epitaxial Growth on Printed Templates.

PubMed

Janneck, Robby; Pilet, Nicolas; Bommanaboyena, Satya Prakash; Watts, Benjamin; Heremans, Paul; Genoe, Jan; Rolin, Cedric

2017-11-01

Highly crystalline thin films of organic semiconductors offer great potential for fundamental material studies as well as for realizing high-performance, low-cost flexible electronics. The fabrication of these films directly on inert substrates is typically done by meniscus-guided coating techniques. The resulting layers show morphological defects that hinder charge transport and induce large device-to-device variability. Here, a double-step method for organic semiconductor layers combining a solution-processed templating layer and a lateral homo-epitaxial growth by a thermal evaporation step is reported. The epitaxial regrowth repairs most of the morphological defects inherent to meniscus-guided coatings. The resulting film is highly crystalline and features a mobility increased by a factor of three and a relative spread in device characteristics improved by almost half an order of magnitude. This method is easily adaptable to other coating techniques and offers a route toward the fabrication of high-performance, large-area electronics based on highly crystalline thin films of organic semiconductors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gas-phase synthesis of semiconductor nanocrystals and its applications

NASA Astrophysics Data System (ADS)

Mandal, Rajib

Luminescent nanomaterials is a newly emerging field that provides challenges not only to fundamental research but also to innovative technology in several areas such as electronics, photonics, nanotechnology, display, lighting, biomedical engineering and environmental control. These nanomaterials come in various forms, shapes and comprises of semiconductors, metals, oxides, and inorganic and organic polymers. Most importantly, these luminescent nanomaterials can have different properties owing to their size as compared to their bulk counterparts. Here we describe the use of plasmas in synthesis, modification, and deposition of semiconductor nanomaterials for luminescence applications. Nanocrystalline silicon is widely known as an efficient and tunable optical emitter and is attracting great interest for applications in several areas. To date, however, luminescent silicon nanocrystals (NCs) have been used exclusively in traditional rigid devices. For the field to advance towards new and versatile applications for nanocrystal-based devices, there is a need to investigate whether these NCs can be used in flexible and stretchable devices. We show how the optical and structural/morphological properties of plasma-synthesized silicon nanocrystals (Si NCs) change when they are deposited on stretchable substrates made of polydimethylsiloxane (PDMS). Synthesis of these NCs was performed in a nonthermal, low-pressure gas phase plasma reactor. To our knowledge, this is the first demonstration of direct deposition of NCs onto stretchable substrates. Additionally, in order to prevent oxidation and enhance the luminescence properties, a silicon nitride shell was grown around Si NCs. We have demonstrated surface nitridation of Si NCs in a single step process using non?thermal plasma in several schemes including a novel dual-plasma synthesis/shell growth process. These coated NCs exhibit SiNx shells with composition depending on process parameters. While measurements including photoluminescence (PL), surface analysis, and defect identification indicate the shell is protective against oxidation compared to Si NCs without any shell growth. Gallium Nitride (GaN) is one of the most well-known semiconductor material and the industry standard for fabricating LEDs. The problem is that epitaxial growth of high-quality GaN requires costly substrates (e.g. sapphire), high temperatures, and long processing times. Synthesizing freestanding NCs of GaN, on the other hand, could enable these novel device morphologies, as the NCs could be incorporated into devices without the requirements imposed by epitaxial GaN growth. Synthesis of GaN NCs was performed using a fully gas-phase process. Different sizes of crystalline GaN nanoparticles were produced indicating versatility of this gas-phase process. Elemental analysis using X-ray photoelectron spectroscopy (XPS) indicated a possible nitrogen deficiency in the NCs; addition of secondary plasma for surface treatment indicates improving stoichiometric ratio and points towards a unique method for creating high-quality GaN NCs with ultimate alloying and doping for full-spectrum luminescence.

Graphene growth process modeling: a physical-statistical approach

NASA Astrophysics Data System (ADS)

Wu, Jian; Huang, Qiang

2014-09-01

As a zero-band semiconductor, graphene is an attractive material for a wide variety of applications such as optoelectronics. Among various techniques developed for graphene synthesis, chemical vapor deposition on copper foils shows high potential for producing few-layer and large-area graphene. Since fabrication of high-quality graphene sheets requires the understanding of growth mechanisms, and methods of characterization and control of grain size of graphene flakes, analytical modeling of graphene growth process is therefore essential for controlled fabrication. The graphene growth process starts with randomly nucleated islands that gradually develop into complex shapes, grow in size, and eventually connect together to cover the copper foil. To model this complex process, we develop a physical-statistical approach under the assumption of self-similarity during graphene growth. The growth kinetics is uncovered by separating island shapes from area growth rate. We propose to characterize the area growth velocity using a confined exponential model, which not only has clear physical explanation, but also fits the real data well. For the shape modeling, we develop a parametric shape model which can be well explained by the angular-dependent growth rate. This work can provide useful information for the control and optimization of graphene growth process on Cu foil.

MOVPE Growth of LWIR AlInAs/GaInAs/InP Quantum Cascade Lasers: Impact of Growth and Material Quality on Laser Performance

DTIC Science & Technology

2017-02-01

MOVPE Growth of LWIR AlInAs/GaInAs/InP Quantum Cascade Lasers: Impact of Growth and Material Quality on Laser Performance (Invited paper) Christine A...epitaxial layers in quantum cascade lasers (QCLs) has a primary impact on QCL operation, and establishing correlations between epitaxial growth and materials...QCLs emitting in this range. Index terms – Quantum cascade lasers, semiconductor growth, semiconductor epitaxial layers, infrared emitters. I

Preface of 16th International conference on Defects, Recognition, Imaging and Physics in Semiconductors

NASA Astrophysics Data System (ADS)

Yang, Deren; Xu, Ke

2016-11-01

The 16th International conference on Defects-Recognition, Imaging and Physics in Semiconductors (DRIP-XVI) was held at the Worldhotel Grand Dushulake in Suzhou, China from 6th to 10th September 2015, around the 30th anniversary of the first DRIP conference. It was hosted by the Suzhou Institute of Nano-tech and Nano-bionics (SINANO), Chinese Academy of Sciences. On this occasion, about one hundred participants from nineteen countries attended the event. And a wide range of subjects were addressed during the conference: physics of point and extended defects in semiconductors: origin, electrical, optical and magnetic properties of defects; diagnostics techniques of crystal growth and processing of semiconductor materials (in-situ and process control); device imaging and mapping to evaluate performance and reliability; defect analysis in degraded optoelectronic and electronic devices; imaging techniques and instruments (proximity probe, x-ray, electron beam, non-contact electrical, optical and thermal imaging techniques, etc.); new frontiers of atomic-scale-defect assessment (STM, AFM, SNOM, ballistic electron energy microscopy, TEM, etc.); new approaches for multi-physic-parameter characterization with Nano-scale space resolution. Within these subjects, there were 58 talks, of which 18 invited, and 50 posters.

Suppression of compensating native defect formation during semiconductor processing via excess carriers

NASA Astrophysics Data System (ADS)

Alberi, K.; Scarpulla, M. A.

2016-06-01

In many semiconductors, compensating defects set doping limits, decrease carrier mobility, and reduce minority carrier lifetime thus limiting their utility in devices. Native defects are often responsible. Suppressing the concentrations of compensating defects during processing close to thermal equilibrium is difficult because formation enthalpies are lowered as the Fermi level moves towards the majority band edge. Excess carriers, introduced for example by photogeneration, modify the formation enthalpy of semiconductor defects and thus can be harnessed during crystal growth or annealing to suppress defect populations. Herein we develop a rigorous and general model for defect formation in the presence of steady-state excess carrier concentrations by combining the standard quasi-chemical formalism with a detailed-balance description that is applicable for any defect state in the bandgap. Considering the quasi-Fermi levels as chemical potentials, we demonstrate that increasing the minority carrier concentration increases the formation enthalpy for typical compensating centers, thus suppressing their formation. This effect is illustrated for the specific example of GaSb. While our treatment is generalized for excess carrier injection or generation in semiconductors by any means, we provide a set of guidelines for applying the concept in photoassisted physical vapor deposition.

Suppression of compensating native defect formation during semiconductor processing via excess carriers

DOE PAGES

Alberi, Kirstin; Scarpulla, M. A.

2016-06-21

In many semiconductors, compensating defects set doping limits, decrease carrier mobility, and reduce minority carrier lifetime thus limiting their utility in devices. Native defects are often responsible. Suppressing the concentrations of compensating defects during processing close to thermal equilibrium is difficult because formation enthalpies are lowered as the Fermi level moves towards the majority band edge. Excess carriers, introduced for example by photogeneration, modify the formation enthalpy of semiconductor defects and thus can be harnessed during crystal growth or annealing to suppress defect populations. Herein we develop a rigorous and general model for defect formation in the presence of steady-statemore » excess carrier concentrations by combining the standard quasi-chemical formalism with a detailed-balance description that is applicable for any defect state in the bandgap. Considering the quasi-Fermi levels as chemical potentials, we demonstrate that increasing the minority carrier concentration increases the formation enthalpy for typical compensating centers, thus suppressing their formation. Furthermore, this effect is illustrated for the specific example of GaSb. While our treatment is generalized for excess carrier injection or generation in semiconductors by any means, we provide a set of guidelines for applying the concept in photoassisted physical vapor deposition.« less

Direct Growth of Graphene on Silicon by Metal-Free Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Tai, Lixuan; Zhu, Daming; Liu, Xing; Yang, Tieying; Wang, Lei; Wang, Rui; Jiang, Sheng; Chen, Zhenhua; Xu, Zhongmin; Li, Xiaolong

2018-06-01

The metal-free synthesis of graphene on single-crystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth of graphene directly on an upside-down placed, single-crystal silicon substrate using metal-free, ambient-pressure chemical vapor deposition. By controlling the growth temperature, in-plane propagation, edge-propagation, and core-propagation, the process of graphene growth on silicon can be identified. This process produces atomically flat monolayer or bilayer graphene domains, concave bilayer graphene domains, and bulging few-layer graphene domains. This work would be a significant step toward the synthesis of large-area and layer-controlled, high-quality graphene on single-crystal silicon substrates. [Figure not available: see fulltext.

Epitaxial thin film growth in outer space

NASA Technical Reports Server (NTRS)

Ignatiev, Alex; Chu, C. W.

1988-01-01

A new concept for materials processing in space exploits the ultravacuum component of space for thin-film epitaxial growth. The unique LEO space environment is expected to yield 10-ftorr or better pressures, semiinfinite pumping speeds, and large ultravacuum volume (about 100 cu m) without walls. These space ultravacuum properties promise major improvement in the quality, unique nature, and throughput of epitaxially grown materials, including semiconductors, magnetic materials, and thin-film high-temperature superconductors.

Structure of CdTe nanoparticles in glass

NASA Astrophysics Data System (ADS)

Hayes, T. M.; Nagpal, Swati; Persans, P. D.

2000-03-01

Optical long-pass wavelength filters are generally made by growing small crystallites of appropriate semiconductors in a transparent glass matrix. Depending on the semiconductor, these systems are candidates for interesting and important nonlinear optical switching applications. The structure of these nanocrystals has been shown to be a valuable indicator of the chemical and thermodynamic processes during crystallite growth and dissolution. We have used x-ray absorption spectroscopy to study the structure of the crystallites produced during heat treatment of filter glasses containing Cd and Te and producing optical absorption edges at the band gap of bulk CdTe. The results will be discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Choong Koo; Park, Hyo Jeong; Kim, In Chool

Reserve margins of Korea Electric Power Corporation (KEPCO) was 12% in 1993, however it was reduced to less than 3% in the summer of 1994 due to increase of electric power consumption caused by life style change based on economic growth. Therefore stable supply of electric power to industrial plant was threatened during last summer`s peak. The process of semiconductor manufacturing is very precious and full processing time reaches several months. Furthermore interruption of power supply to the process causes abortion of every product in the process. Therefore, power failure of less than one (1) second, may result in enormousmore » loss of capital. In order to protect disaster caused by power shortage during summer peaks. Samsung Electronics Co., Ltd (SEC) planned to construct LNG combined cycle power plant for the Klheung semiconductor plant which is the world`s leading maker of dynamic random access memory (DRAM) chips.« less

The materials processing research base of the Materials Processing Center

NASA Technical Reports Server (NTRS)

Latanision, R. M.

1986-01-01

An annual report of the research activities of the Materials Processing Center of the Massachusetts Institute of Technology is given. Research on dielectrophoresis in the microgravity environment, phase separation kinetics in immiscible liquids, transport properties of droplet clusters in gravity-free fields, probes and monitors for the study of solidification of molten semiconductors, fluid mechanics and mass transfer in melt crystal growth, and heat flow control and segregation in directional solidification are discussed.

Interfacial oxide re-growth in thin film metal oxide III-V semiconductor systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDonnell, S.; Dong, H.; Hawkins, J. M.

2012-04-02

The Al{sub 2}O{sub 3}/GaAs and HfO{sub 2}/GaAs interfaces after atomic layer deposition are studied using in situ monochromatic x-ray photoelectron spectroscopy. Samples are deliberately exposed to atmospheric conditions and interfacial oxide re-growth is observed. The extent of this re-growth is found to depend on the dielectric material and the exposure temperature. Comparisons with previous studies show that ex situ characterization can result in misleading conclusions about the interface reactions occurring during the metal oxide deposition process.

Landau quantization effects on hole-acoustic instability in semiconductor plasmas

NASA Astrophysics Data System (ADS)

Sumera, P.; Rasheed, A.; Jamil, M.; Siddique, M.; Areeb, F.

2017-12-01

The growth rate of the hole acoustic waves (HAWs) exciting in magnetized semiconductor quantum plasma pumped by the electron beam has been investigated. The instability of the waves contains quantum effects including the exchange and correlation potential, Bohm potential, Fermi-degenerate pressure, and the magnetic quantization of semiconductor plasma species. The effects of various plasma parameters, which include relative concentration of plasma particles, beam electron temperature, beam speed, plasma temperature (temperature of electrons/holes), and Landau electron orbital magnetic quantization parameter η, on the growth rate of HAWs, have been discussed. The numerical study of our model of acoustic waves has been applied, as an example, to the GaAs semiconductor exposed to electron beam in the magnetic field environment. An increment in either the concentration of the semiconductor electrons or the speed of beam electrons, in the presence of magnetic quantization of fermion orbital motion, enhances remarkably the growth rate of the HAWs. Although the growth rate of the waves reduces with a rise in the thermal temperature of plasma species, at a particular temperature, we receive a higher instability due to the contribution of magnetic quantization of fermions to it.

Synthesis and characterization of metal oxide semiconductors by a facile co-electroplating-annealing method and formation of ZnO/CuO pn heterojunctions with rectifying behavior

NASA Astrophysics Data System (ADS)

Turkdogan, Sunay; Kilic, Bayram

2018-01-01

We have developed a unique growth method and demonstrated the growth of CuO and ZnO semiconductor materials and the fabrication of their pn heterojunctions in ambient atmosphere. The pn heterojunctions were constructed using inherently p-type CuO and inherently n-type ZnO materials. Both p- and n-type semiconductors and pn heterojunctions were prepared using a simple but versatile growth method that relies on the transformation of electroplated Cu and Zn metals into CuO and ZnO semiconductors, respectively and is capable of a large-scale production desired in most of the applications. The structural, chemical, optical and electrical properties of the materials and junctions were investigated using various characterization methods and the results show that our growth method, materials and devices are quite promising to be utilized for various applications including but not limited to solar cells, gas/humidity sensors and photodetectors.

Growth of Wide Band Gap II-VI Compound Semiconductors by Physical Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Sha, Yi-Gao

1995-01-01

The studies on the crystal growth and characterization of II-VI wide band gap compound semiconductors, such as ZnTe, CdS, ZnSe and ZnS, have been conducted over the past three decades. The research was not quite as extensive as that on Si, III-V, or even narrow band gap II-VI semiconductors because of the high melting temperatures as well as the specialized applications associated with these wide band gap semiconductors. In the past several years, major advances in the thin film technology such as Molecular Beam Epitaxy (MBE) and Metal Organic Chemical Vapor Deposition (MOCVD) have demonstrated the applications of these materials for the important devices such as light-emitting diode, laser and ultraviolet detectors and the tunability of energy band gap by employing ternary or even quaternary systems of these compounds. At the same time, the development in the crystal growth of bulk materials has not advanced far enough to provide low price, high quality substrates needed for the thin film growth technology.

Thermophysical Property Measurements of Molten Semiconductors in 1-g and Reduced-g Condition

NASA Technical Reports Server (NTRS)

Rhim, Won-Kyu

1999-01-01

Understanding and controlling the formation kinetics of varieties of crystal imperfections such as point defects, non uniform distribution of doping atoms, and impurity atoms in growing crystals are very important. Theoretical (numerical) modeling of the crystal growth process is an essential step to achieving these objectives. In order to obtain reliable modeling results, input parameters, i.e. various thermophysical parameters, must be accurate. The importance of accurate thermophysical properties of semiconductors in crystal growth cannot be overly emphasized. The total hemispherical emissivity, for instance, has a dramatic impact on the thermal environment. It determines the radiative emission from the surface of the melt which determines to a large extent the profile of the solidified crystal. In order to understand the convection and the turbulence in a melt, viscosity becomes an important parameter. The liquid surface tension determines the shape of the liquid-atmosphere interface near the solid-liquid-atmosphere triple point. Currently used values for these parameters are rather inaccurate, and this program intends to provide more reliable measurements of these thermophysical properties. Thus, the objective of this program is in the accurate measurements of various thermophysical properties which can be reliably used in the modeling of various crystal growth processes. In this program, thermophysical properties of molten semiconductors, such as Si, Ge, Si-Ge, and InSb will be measured as a function of temperature using the High Temperature Electrostatic Levitator at JPL. Each material will be doped by different kinds of impurities at various doping levels. Thermophysical properties which will be measured include: density, thermal expansion coefficient, surface tension, viscosity, specific heat, hemispherical total emissivity, and perhaps electrical and thermal conductivities. Many molten semiconductors are chemically reactive with crucibles. As a result, these dispersed impurities in the melts tend to substantially modify the properties of pure semiconductors. Sample levitation done in a vacuum clearly helps maintain the sample purity. However, in the 1-g environment, all gravity caused effects such as convection, sedimentation and buoyancy are still present in the sample. In addition, large forces needed to levitate a sample in the presence of the gravity can cause additional flows in the melt. The use of the High Temperature Electrostatic Levitator (HTESL) for the present research is a recent development and little is known about the flows induced by the electrostatic forces. In this ground base program, we will define the limits of HTESL technology as various thermophysical properties of molten semiconductors are measured.

Research study on materials processing in space, experiment M512

NASA Technical Reports Server (NTRS)

Rubenstein, M.; Hopkins, R. H.; Kim, H. B.

1973-01-01

Gallium arsenide, a commercially valuable semiconductor, has been prepared from the melt (M.P. 1237C), by vapor growth, and by growth from metallic solutions. It has been established that growth from metallic solution can produce material with high, and perhaps with the highest possible, chemical homogeneity and crystalline perfection. Growth of GaAs from metallic solution can be performed at relatively low temperatures (about 600C) and is relatively insensitive to temperature fluctuations. However, this type of crystal growth is subject to the decided disadvantage that density induced convection currents may produce variations in rates of growth at a growing surface. This problem would be minimized under reduced gravity conditions.

Evolution of corundum-structured III-oxide semiconductors: Growth, properties, and devices

NASA Astrophysics Data System (ADS)

Fujita, Shizuo; Oda, Masaya; Kaneko, Kentaro; Hitora, Toshimi

2016-12-01

The recent progress and development of corundum-structured III-oxide semiconductors are reviewed. They allow bandgap engineering from 3.7 to ∼9 eV and function engineering, leading to highly durable electronic devices and deep ultraviolet optical devices as well as multifunctional devices. Mist chemical vapor deposition can be a simple and safe growth technology and is advantageous for reducing energy and cost for the growth. This is favorable for the wide commercial use of devices at low cost. The III-oxide semiconductors are promising candidates for new devices contributing to sustainable social, economic, and technological development for the future.

Process for the controlled growth of single-crystal films of silicon carbide polytypes on silicon carbide wafers

NASA Technical Reports Server (NTRS)

Powell, J. Anthony (Inventor)

1991-01-01

This invention is a method for the controlled growth of single-crystal semiconductor device quality films of SiC polytypes on vicinal (0001) SiC wafers with low tilt angles. Both homoepitaxial and heteroepitaxial SiC films can be produced on the same wafer. In particular, 3C-SiC and 6H-SiC films can be produced within selected areas of the same 6H-SiC wafer.

Process for the controlled growth of single-crystal films of silicon carbide polytypes on silicon carbide wafers

NASA Technical Reports Server (NTRS)

Larkin, David J. (Inventor); Powell, J. Anthony (Inventor)

1992-01-01

A method for the controlled growth of single-crystal semiconductor-device-quality films of SiC polytypes on vicinal (0001) SiC wafers with low tilt angles is presented. Both homoepitaxial and heteroepitaxial SiC films can be produced on the same wafer. In particular, 3C-SiC and 6H-SiC films can be produced within selected areas of the same 6H-SiC wafer.

Process for selectively patterning epitaxial film growth on a semiconductor substrate

DOEpatents

Sheldon, P.; Hayes, R.E.

1984-12-04

Disclosed is a process for selectively patterning epitaxial film growth on a semiconductor substrate. The process includes forming a masking member on the surface of the substrate, the masking member having at least two layers including a first layer disposed on the substrate and the second layer covering the first layer. A window is then opened in a selected portion of the second layer by removing that portion to expose the first layer thereunder. The first layer is then subjected to an etchant introduced through the window to dissolve the first layer a sufficient amount to expose the substrate surface directly beneath the window, the first layer being adapted to preferentially dissolve at a substantially greater rate than the second layer so as to create an overhanging ledge portion with the second layer by undercutting the edges thereof adjacent the window. The epitaxial film is then deposited on the exposed substrate surface directly beneath the window. Finally, an etchant is introduced through the window to dissolve the remainder of the first layer so as to lift-off the second layer and materials deposited thereon to fully expose the balance of the substrate surface.

Process for selectively patterning epitaxial film growth on a semiconductor substrate

DOEpatents

Sheldon, Peter; Hayes, Russell E.

1986-01-01

A process is disclosed for selectively patterning epitaxial film growth on a semiconductor substrate. The process includes forming a masking member on the surface of the substrate, the masking member having at least two layers including a first layer disposed on the substrate and the second layer covering the first layer. A window is then opened in a selected portion of the second layer by removing that portion to expose the first layer thereunder. The first layer is then subjected to an etchant introduced through the window to dissolve a sufficient amount of the first layer to expose the substrate surface directly beneath the window, the first layer being adapted to preferentially dissolve at a substantially greater rate than the second layer so as to create an overhanging ledge portion with the second layer by undercutting the edges thereof adjacent to the window. The epitaxial film is then deposited on the exposed substrate surface directly beneath the window. Finally, an etchant is introduced through the window to dissolve the remainder of the first layer so as to lift-off the second layer and materials deposited thereon to fully expose the balance of the substrate surface.

Trap densities and transport properties of pentacene metal-oxide-semiconductor transistors. I. Analytical modeling of time-dependent characteristics

NASA Astrophysics Data System (ADS)

Basile, A. F.; Cramer, T.; Kyndiah, A.; Biscarini, F.; Fraboni, B.

2014-06-01

Metal-oxide-semiconductor (MOS) transistors fabricated with pentacene thin films were characterized by temperature-dependent current-voltage (I-V) characteristics, time-dependent current measurements, and admittance spectroscopy. The channel mobility shows almost linear variation with temperature, suggesting that only shallow traps are present in the semiconductor and at the oxide/semiconductor interface. The admittance spectra feature a broad peak, which can be modeled as the sum of a continuous distribution of relaxation times. The activation energy of this peak is comparable to the polaron binding energy in pentacene. The absence of trap signals in the admittance spectra confirmed that both the semiconductor and the oxide/semiconductor interface have negligible density of deep traps, likely owing to the passivation of SiO2 before pentacene growth. Nevertheless, current instabilities were observed in time-dependent current measurements following the application of gate-voltage pulses. The corresponding activation energy matches the energy of a hole trap in SiO2. We show that hole trapping in the oxide can explain both the temperature and the time dependences of the current instabilities observed in pentacene MOS transistors. The combination of these experimental techniques allows us to derive a comprehensive model for charge transport in hybrid architectures where trapping processes occur at various time and length scales.

Visualization of TlBr ionic transport mechanism by the Accelerated Device Degradation technique

NASA Astrophysics Data System (ADS)

Datta, Amlan; Becla, Piotr; Motakef, Shariar

2015-06-01

Thallium Bromide (TlBr) is a promising gamma radiation semiconductor detector material. However, it is an ionic semiconductor and suffers from polarization. As a result, TlBr devices degrade rapidly at room temperature. Polarization is associated with the flow of ionic current in the crystal under electrical bias, leading to the accumulation of charged ions at the device's electrical contacts. We report a fast and reliable direct characterization technique to identify the effects of various growth and post-growth process modifications on the polarization process. The Accelerated Device Degradation (ADD) characterization technique allows direct observation of nucleation and propagation of ionic transport channels within the TlBr crystals under applied bias. These channels are observed to be initiated both directly under the electrode as well as away from it. The propagation direction is always towards the anode indicating that Br- is the mobile diffusing species within the defect channels. The effective migration energy of the Br- ions was calculated to be 0.33±0.03 eV, which is consistent with other theoretical and experimental results.

Intrinsic and extrinsic parameters for controlling the growth of organic single-crystalline nanopillars in photovoltaics.

PubMed

Zhang, Yue; Diao, Ying; Lee, Hyunbok; Mirabito, Timothy J; Johnson, Richard W; Puodziukynaite, Egle; John, Jacob; Carter, Kenneth R; Emrick, Todd; Mannsfeld, Stefan C B; Briseno, Alejandro L

2014-10-08

The most efficient architecture for achieving high donor/acceptor interfacial area in organic photovoltaics (OPVs) would employ arrays of vertically interdigitated p- and n- type semiconductor nanopillars (NPs). Such morphology could have an advantage in bulk heterojunction systems; however, precise control of the dimension morphology in a crystalline, interpenetrating architecture has not yet been realized. Here we present a simple, yet facile, crystallization technique for the growth of vertically oriented NPs utilizing a modified thermal evaporation technique that hinges on a fast deposition rate, short substrate-source distance, and ballistic mass transport. A broad range of organic semiconductor materials is beneficial from the technique to generate NP geometries. Moreover, this technique can also be generalized to various substrates, namely, graphene, PEDOT-PSS, ZnO, CuI, MoO3, and MoS2. The advantage of the NP architecture over the conventional thin film counterpart is demonstrated with an increase of power conversion efficiency of 32% in photovoltaics. This technique will advance the knowledge of organic semiconductor crystallization and create opportunities for the fabrication and processing of NPs for applications that include solar cells, charge storage devices, sensors, and vertical transistors.

Suppression of planar defects in the molecular beam epitaxy of GaAs/ErAs/GaAs heterostructures

NASA Astrophysics Data System (ADS)

Crook, Adam M.; Nair, Hari P.; Ferrer, Domingo A.; Bank, Seth R.

2011-08-01

We present a growth method that overcomes the mismatch in rotational symmetry of ErAs and conventional III-V semiconductors, allowing for epitaxially integrated semimetal/semiconductor heterostructures. Transmission electron microscopy and reflection high-energy electron diffraction reveal defect-free overgrowth of ErAs layers, consisting of >2× the total amount of ErAs that can be embedded with conventional layer-by-layer growth methods. We utilize epitaxial ErAs nanoparticles, overgrown with GaAs, as a seed to grow full films of ErAs. Growth proceeds by diffusion of erbium atoms through the GaAs spacer, which remains registered to the underlying substrate, preventing planar defect formation during subsequent GaAs growth. This growth method is promising for metal/semiconductor heterostructures that serve as embedded Ohmic contacts to epitaxial layers and epitaxially integrated active plasmonic devices.

Conductive layer for biaxially oriented semiconductor film growth

DOEpatents

Findikoglu, Alp T.; Matias, Vladimir

2007-10-30

A conductive layer for biaxially oriented semiconductor film growth and a thin film semiconductor structure such as, for example, a photodetector, a photovoltaic cell, or a light emitting diode (LED) that includes a crystallographically oriented semiconducting film disposed on the conductive layer. The thin film semiconductor structure includes: a substrate; a first electrode deposited on the substrate; and a semiconducting layer epitaxially deposited on the first electrode. The first electrode includes a template layer deposited on the substrate and a buffer layer epitaxially deposited on the template layer. The template layer includes a first metal nitride that is electrically conductive and has a rock salt crystal structure, and the buffer layer includes a second metal nitride that is electrically conductive. The semiconducting layer is epitaxially deposited on the buffer layer. A method of making such a thin film semiconductor structure is also described.

Semiconductor neutron detectors

NASA Astrophysics Data System (ADS)

Gueorguiev, Andrey; Hong, Huicong; Tower, Joshua; Kim, Hadong; Cirignano, Leonard; Burger, Arnold; Shah, Kanai

2016-09-01

Lithium Indium Selenide (LiInSe2) has been under development in RMD Inc. and Fisk University for room temperature thermal neutron detection due to a number of promising properties. The recent advances of the crystal growth, material processing, and detector fabrication technologies allowed us to fabricate large detectors with 100 mm2 active area. The thermal neutron detection sensitivity and gamma rejection ratio (GRR) were comparable to 3He tube with 10 atm gas pressure at comparable dimensions. The synthesis, crystal growth, detector fabrication, and characterization are reported in this paper.

Commercial aspects of epitaxial thin film growth in outer space

NASA Technical Reports Server (NTRS)

Ignatiev, Alex; Chu, C. W.

1988-01-01

A new concept for materials processing in space exploits the ultra vacuum component of space for thin film epitaxial growth. The unique low earth orbit space environment is expected to yield 10 to the -14th torr or better pressures, semiinfinite pumping speeds and large ultra vacuum volume (about 100 cu m) without walls. These space ultra vacuum properties promise major improvement in the quality, unique nature, and the throughput of epitaxially grown materials especially in the area of semiconductors for microelectronics use. For such thin film materials there is expected a very large value added from space ultra vacuum processing, and as a result the application of the epitaxial thin film growth technology to space could lead to major commercial efforts in space.

Surface Stability and Growth Kinetics of Compound Semiconductors: An Ab Initio-Based Approach

PubMed Central

Kangawa, Yoshihiro; Akiyama, Toru; Ito, Tomonori; Shiraishi, Kenji; Nakayama, Takashi

2013-01-01

We review the surface stability and growth kinetics of III-V and III-nitride semiconductors. The theoretical approach used in these studies is based on ab initio calculations and includes gas-phase free energy. With this method, we can investigate the influence of growth conditions, such as partial pressure and temperature, on the surface stability and growth kinetics. First, we examine the feasibility of this approach by comparing calculated surface phase diagrams of GaAs(001) with experimental results. In addition, the Ga diffusion length on GaAs(001) during molecular beam epitaxy is discussed. Next, this approach is systematically applied to the reconstruction, adsorption and incorporation on various nitride semiconductor surfaces. The calculated results for nitride semiconductor surface reconstructions with polar, nonpolar, and semipolar orientations suggest that adlayer reconstructions generally appear on the polar and the semipolar surfaces. However, the stable ideal surface without adsorption is found on the nonpolar surfaces because the ideal surface satisfies the electron counting rule. Finally, the stability of hydrogen and the incorporation mechanisms of Mg and C during metalorganic vapor phase epitaxy are discussed. PMID:28811438

Thermal system design and modeling of meniscus controlled silicon growth process for solar applications

NASA Astrophysics Data System (ADS)

Wang, Chenlei

The direct conversion of solar radiation to electricity by photovoltaics has a number of significant advantages as an electricity generator. That is, solar photovoltaic conversion systems tap an inexhaustible resource which is free of charge and available anywhere in the world. Roofing tile photovoltaic generation, for example, saves excess thermal heat and preserves the local heat balance. This means that a considerable reduction of thermal pollution in densely populated city areas can be attained. A semiconductor can only convert photons with the energy of the band gap with good efficiency. It is known that silicon is not at the maximum efficiency but relatively close to it. There are several main parts for the photovoltaic materials, which include, single- and poly-crystalline silicon, ribbon silicon, crystalline thin-film silicon, amorphous silicon, copper indium diselenide and related compounds, cadmium telluride, et al. In this dissertation, we focus on melt growth of the single- and poly-crystalline silicon manufactured by Czochralski (Cz) crystal growth process, and ribbon silicon produced by the edge-defined film-fed growth (EFG) process. These two methods are the most commonly used techniques for growing photovoltaic semiconductors. For each crystal growth process, we introduce the growth mechanism, growth system design, general application, and progress in the numerical simulation. Simulation results are shown for both Czochralski and EFG systems including temperature distribution of the growth system, velocity field inside the silicon melt and electromagnetic field for the EFG growth system. Magnetic field is applied on Cz system to reduce the melt convection inside crucible and this has been simulated in our numerical model. Parametric studies are performed through numerical and analytical models to investigate the relationship between heater power levels and solidification interface movement and shape. An inverse problem control scheme is developed to control the solidification interface of Cz system by adjusting heater powers. For the EFG system, parametric studies are performed to discuss the effect of several growth parameters including window opening size, argon gas flow rate and growth thermal environment on the temperature distribution, silicon tube thickness and pulling rate. Two local models are developed and integrated with the global model to investigate the detailed transport phenomena in a small region around the solidification interface including silicon crystal, silicon melt, free surface, liquid-solid interface and graphite die design. Different convection forms are taken into consideration.

High-efficiency, thin-film cadmium telluride photovoltaic cells

NASA Astrophysics Data System (ADS)

Compaan, A. D.; Bohn, R. G.; Rajakarunanayake, Y.

1995-08-01

This report describes work performed to develop and optimize the process of radio frequency (RF) sputtering for the fabrication of thin-film solar cells on glass. The emphasis is on CdTe-related materials including CdTe, CdS, ZnTe, and ternary alloy semiconductors. Pulsed laser physical vapor deposition (LPVD) was used for exploratory work on these materials, especially where alloying or doping are involved, and for the deposition of cadmium chloride layers. For the sputtering work, a two-gun sputtering chamber was implemented, with optical access for monitoring temperature and growth rate. We studied the optical and electrical properties of the plasmas produced by two different kinds of planar magnetron sputter guns with different magnetic field configurations and strengths. Using LPVD, we studied alloy semiconductors such as CdZnTe and heavily doped semiconductors such as ZnTe:Cu for possible incorporation into graded band gap CdTe-based photovoltaic devices.

Femtosecond Carrier Processes in Compound Semiconductors and Real Time Signal Processing

DTIC Science & Technology

1993-03-10

Blocks in Real Schur Form" ................... 179 5. "The Periodic Schur Decomposition. Algorithms and A p p lication s...existence of short period superlattices (confined LO GaAs and AlAs vibrations) on all samples produced with this method. The degret of deposition zone...small amount of zone intermixing occurs in the spatially separated growth mode (see 1 Figure 1b), the short period superlattices have graded interfaces

An Optoelectronics Research Center

DTIC Science & Technology

2006-03-08

compared with a -2 mm wide slab, -200 nrn thick silicon (SOl) top-only-gate planar MOSFET with otherwise similar doping profiles, gate length and...acoustic phonons, impurity doping profile and surface roughness influences the transport process in the channel regions. The electron mobility in the...application areas including: nanoscale epitaxial growth for semiconductor heterostructures; nanofluidics for biological separations; nanomagnetics for

Epitaxial Growth of Cubic Crystalline Semiconductor Alloys on Basal Plane of Trigonal or Hexagonal Crystal

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor)

2011-01-01

Hetero-epitaxial semiconductor materials comprising cubic crystalline semiconductor alloys grown on the basal plane of trigonal and hexagonal substrates, in which misfit dislocations are reduced by approximate lattice matching of the cubic crystal structure to underlying trigonal or hexagonal substrate structure, enabling the development of alloyed semiconductor layers of greater thickness, resulting in a new class of semiconductor materials and corresponding devices, including improved hetero-bipolar and high-electron mobility transistors, and high-mobility thermoelectric devices.

Solution-processed, Self-organized Organic Single Crystal Arrays with Controlled Crystal Orientation

PubMed Central

Kumatani, Akichika; Liu, Chuan; Li, Yun; Darmawan, Peter; Takimiya, Kazuo; Minari, Takeo; Tsukagoshi, Kazuhito

2012-01-01

A facile solution process for the fabrication of organic single crystal semiconductor devices which meets the demand for low-cost and large-area fabrication of high performance electronic devices is demonstrated. In this paper, we develop a bottom-up method which enables direct formation of organic semiconductor single crystals at selected locations with desired orientations. Here oriented growth of one-dimensional organic crystals is achieved by using self-assembly of organic molecules as the driving force to align these crystals in patterned regions. Based upon the self-organized organic single crystals, we fabricate organic field effect transistor arrays which exhibit an average field-effect mobility of 1.1 cm2V−1s−1. This method can be carried out under ambient atmosphere at room temperature, thus particularly promising for production of future plastic electronics. PMID:22563523

Primary research efforts on exploring the commercial possibilities of thin film growth and materials purification in space

NASA Technical Reports Server (NTRS)

1989-01-01

The progress made on research programs in the 1987 to 1988 year is reported. The research is aimed at producing thin film semiconductors and superconductor materials in space. Sophisticated vacuum chambers and equipment were attained for the epitaxial thin film growth of semiconductors, metals and superconductors. In order to grow the best possible epitaxial films at the lowest possible temperatures on earth, materials are being isoelectronically doped during growth. It was found that isoelectrically doped film shows the highest mobility in comparison with films grown at optimal temperatures. Success was also attained in growing epitaxial films of InSb on sapphire which show promise for infrared sensitive devices in the III-V semiconductor system.

Heteroepitaxial growth of 3-5 semiconductor compounds by metal-organic chemical vapor deposition for device applications

NASA Technical Reports Server (NTRS)

Collis, Ward J.; Abul-Fadl, Ali

1988-01-01

The purpose of this research is to design, install and operate a metal-organic chemical vapor deposition system which is to be used for the epitaxial growth of 3-5 semiconductor binary compounds, and ternary and quaternary alloys. The long-term goal is to utilize this vapor phase deposition in conjunction with existing current controlled liquid phase epitaxy facilities to perform hybrid growth sequences for fabricating integrated optoelectronic devices.

Investigations on Substrate Temperature-Induced Growth Modes of Organic Semiconductors at Dielectric/semiconductor Interface and Their Correlation with Threshold Voltage Stability in Organic Field-Effect Transistors.

PubMed

Padma, Narayanan; Maheshwari, Priya; Bhattacharya, Debarati; Tokas, Raj B; Sen, Shashwati; Honda, Yoshihide; Basu, Saibal; Pujari, Pradeep Kumar; Rao, T V Chandrasekhar

2016-02-10

Influence of substrate temperature on growth modes of copper phthalocyanine (CuPc) thin films at the dielectric/semiconductor interface in organic field effect transistors (OFETs) is investigated. Atomic force microscopy (AFM) imaging at the interface reveals a change from 'layer+island' to "island" growth mode with increasing substrate temperatures, further confirmed by probing the buried interfaces using X-ray reflectivity (XRR) and positron annihilation spectroscopic (PAS) techniques. PAS depth profiling provides insight into the details of molecular ordering while positron lifetime measurements reveal the difference in packing modes of CuPc molecules at the interface. XRR measurements show systematic increase in interface width and electron density correlating well with the change from layer + island to coalesced huge 3D islands at higher substrate temperatures. Study demonstrates the usefulness of XRR and PAS techniques to study growth modes at buried interfaces and reveals the influence of growth modes of semiconductor at the interface on hole and electron trap concentrations individually, thereby affecting hysteresis and threshold voltage stability. Minimum hole trapping is correlated to near layer by layer formation close to the interface at 100 °C and maximum to the island formation with large voids between the grains at 225 °C.

Review Article: Overview of lanthanide pnictide films and nanoparticles epitaxially incorporated into III-V semiconductors

DOE PAGES

Bomberger, Cory C.; Lewis, Matthew R.; Vanderhoef, Laura R.; ...

2017-03-30

The incorporation of lanthanide pnictide nanoparticles and films into III-V matrices allows for semiconductor composites with a wide range of potential optical, electrical, and thermal properties, making them useful for applications in thermoelectrics, tunnel junctions, phototconductive switches, and as contact layers. The similarities in crystal structures and lattice constants allow them to be epitaxially incorporated into III-V semiconductors with low defect densities and high overall film quality. A variety of growth techniques for these composites with be discussed, along with their growth mechanisms and current applications, with a focus on more recent developments. Results obtained from molecular beam epitaxy filmmore » growth will be highlighted, although other growth techniques will be mentioned. Optical and electronic characterization along with the microscopy analysis of these composites is presented to demonstrate influence of nanoinclusion composition and morphology on the resulting properties of the composite material.« less

Review Article: Overview of lanthanide pnictide films and nanoparticles epitaxially incorporated into III-V semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bomberger, Cory C.; Lewis, Matthew R.; Vanderhoef, Laura R.

The incorporation of lanthanide pnictide nanoparticles and films into III-V matrices allows for semiconductor composites with a wide range of potential optical, electrical, and thermal properties, making them useful for applications in thermoelectrics, tunnel junctions, phototconductive switches, and as contact layers. The similarities in crystal structures and lattice constants allow them to be epitaxially incorporated into III-V semiconductors with low defect densities and high overall film quality. A variety of growth techniques for these composites with be discussed, along with their growth mechanisms and current applications, with a focus on more recent developments. Results obtained from molecular beam epitaxy filmmore » growth will be highlighted, although other growth techniques will be mentioned. Optical and electronic characterization along with the microscopy analysis of these composites is presented to demonstrate influence of nanoinclusion composition and morphology on the resulting properties of the composite material.« less

Nanoengineering of strong field processes in solids

NASA Astrophysics Data System (ADS)

Almalki, S.; Parks, A. M.; Brabec, T.; McDonald, C. R.

2018-04-01

We present a theoretical investigation of the effect of quantum confinement on high harmonic generation in semiconductor materials by systematically varying the confinement width along one or two directions transverse to the laser polarization. Our analysis shows a growth in high harmonic efficiency concurrent with a reduction of ionization. This decrease in ionization comes as a consequence of an increased band gap resulting from the confinement. The increase in harmonic efficiency results from a restriction of wave packet spreading, leading to greater recollision probability. Consequently, nanoengineering of one and two-dimensional nanosystems may prove to be a viable means to increase harmonic yield and photon energy in semiconductor materials driven by intense laser fields.

Bridgman growth of semiconductors

NASA Technical Reports Server (NTRS)

Carlson, F. M.

1985-01-01

The purpose of this study was to improve the understanding of the transport phenomena which occurs in the directional solidification of alloy semiconductors. In particular, emphasis was placed on the strong role of convection in the melt. Analytical solutions were not deemed possible for such an involved problem. Accordingly, a numerical model of the process was developed which simulated the transport. This translates into solving the partial differential equations of energy, mass, species, and momentum transfer subject to various boundary and initial conditions. A finite element method with simple elements was initially chosen. This simulation tool will enable the crystal grower to systematically identify and modify the important design factors within her control to produce better crystals.

Filamentation of a surface plasma wave over a semiconductor-free space interface

NASA Astrophysics Data System (ADS)

Kumar, Gagan; Tripathi, V. K.

2007-12-01

A large amplitude surface plasma wave (SPW), propagating over a semiconductor-free space interface, is susceptible to filamentation instability. A small perturbation in the amplitude of the SPW across the direction of propagation exerts a ponderomotive force on free electrons and holes, causing spatial modulation in free carrier density and hence the effective permittivity ɛeff of the semiconductor. The regions with higher ɛeff attract more power from the nieghborhood, leading to the growth of the perturbation. The growth rate increases with the intensity of the surface wave. It decreases with the frequency of the SPW.

Methods for growth of relatively large step-free SiC crystal surfaces

NASA Technical Reports Server (NTRS)

Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor)

2002-01-01

A method for growing arrays of large-area device-size films of step-free (i.e., atomically flat) SiC surfaces for semiconductor electronic device applications is disclosed. This method utilizes a lateral growth process that better overcomes the effect of extended defects in the seed crystal substrate that limited the obtainable step-free area achievable by prior art processes. The step-free SiC surface is particularly suited for the heteroepitaxial growth of 3C (cubic) SiC, AlN, and GaN films used for the fabrication of both surface-sensitive devices (i.e., surface channel field effect transistors such as HEMT's and MOSFET's) as well as high-electric field devices (pn diodes and other solid-state power switching devices) that are sensitive to extended crystal defects.

Shallow melt apparatus for semicontinuous czochralski crystal growth

DOEpatents

Wang, Tihu; Ciszek, Theodore F.

2006-01-10

In a single crystal pulling apparatus for providing a Czochralski crystal growth process, the improvement of a shallow melt In a single crystal pulling apparatus for providing a Czochralski crystal growth process, the improvement of a shallow melt crucible (20) to eliminate the necessity supplying a large quantity of feed stock materials that had to be preloaded in a deep crucible to grow a large ingot, comprising a gas tight container a crucible with a deepened periphery (25) to prevent snapping of a shallow melt and reduce turbulent melt convection; source supply means for adding source material to the semiconductor melt; a double barrier (23) to minimize heat transfer between the deepened periphery (25) and the shallow melt in the growth compartment; offset holes (24) in the double barrier (23) to increase melt travel length between the deepened periphery (25) and the shallow growth compartment; and the interface heater/heat sink (22) to control the interface shape and crystal growth rate.

Seeded Nanowire and Microwire Growth from Lithium Alloys.

PubMed

Han, Sang Yun; Boebinger, Matthew G; Kondekar, Neha P; Worthy, Trevor J; McDowell, Matthew T

2018-06-06

Although vapor-liquid-solid (VLS) growth of nanowires from alloy seed particles is common in various semiconductor systems, related wire growth in all-metal systems is rare. Here, we report the spontaneous growth of nano- and microwires from metal seed particles during the cooling of Li-rich bulk alloys containing Au, Ag, or In. The as-grown wires feature Au-, Ag-, or In-rich metal tips and LiOH shafts; the results indicate that the wires grow as Li metal and are converted to polycrystalline LiOH during and/or after growth due to exposure to H 2 O and O 2 . This new process is a simple way to create nanostructures, and the findings suggest that metal nanowire growth from alloy seeds is possible in a variety of systems.

The initial stages of ZnO atomic layer deposition on atomically flat In0.53Ga0.47As substrates.

PubMed

Skopin, Evgeniy V; Rapenne, Laetitia; Roussel, Hervé; Deschanvres, Jean-Luc; Blanquet, Elisabeth; Ciatto, Gianluca; Fong, Dillon D; Richard, Marie-Ingrid; Renevier, Hubert

2018-06-21

InGaAs is one of the III-V active semiconductors used in modern high-electron-mobility transistors or high-speed electronics. ZnO is a good candidate material to be inserted as a tunneling insulator layer at the metal-semiconductor junction. A key consideration in many modern devices is the atomic structure of the hetero-interface, which often ultimately governs the electronic or chemical process of interest. Here, a complementary suite of in situ synchrotron X-ray techniques (fluorescence, reflectivity and absorption) as well as modeling is used to investigate both structural and chemical evolution during the initial growth of ZnO by atomic layer deposition (ALD) on In0.53Ga0.47As substrates. Prior to steady-state growth behavior, we discover a transient regime characterized by two stages. First, substrate-inhibited ZnO growth takes place on InGaAs terraces. This leads eventually to the formation of a 1 nm-thick, two-dimensional (2D) amorphous layer. Second, the growth behavior and its modeling suggest the occurrence of dense island formation, with an aspect ratio and surface roughness that depends sensitively on the growth condition. Finally, ZnO ALD on In0.53Ga0.47As is characterized by 2D steady-state growth with a linear growth rate of 0.21 nm cy-1, as expected for layer-by-layer ZnO ALD.

Laser-processing of VO2 thin films synthesized by polymer-assisted-deposition

NASA Astrophysics Data System (ADS)

Breckenfeld, Eric; Kim, Heungsoo; Gorzkowski, Edward P.; Sutto, Thomas E.; Piqué, Alberto

2017-03-01

We investigate a novel route for synthesis and laser-sintering of VO2 thin films via solution-based polymer-assisted-deposition (PAD). By replacing the traditional solvent for PAD (water) with propylene glycol, we are able to control the viscosity and improve the environmental stability of the precursor. The solution stability and ability to control the viscosity makes for an ideal solution to pattern simple or complex shapes via direct-write methods. We demonstrate the potential of our precursor for printing applications by combining PAD with laser induced forward transfer (LIFT). We also demonstrate large-area film synthesis on 4 in. diameter glass wafers. By varying the annealing temperature, we identify the optimal synthesis conditions, obtaining optical transmittance changes of 60% at a 2500 nm wavelength and a two-order-of-magnitude semiconductor-to-metal transition. We go on to demonstrate two routes for improved semiconductor-to-metal characteristics. The first method uses a multi-coating process to produce denser films with large particles. The second method uses a pulsed-UV-laser sintering step in films annealed at low temperatures (<450° C) to promote particle growth and improve the semiconductor-to-metal transition. By comparing the hysteresis width and semiconductor-to-metal transition magnitude in these samples, we demonstrate that both methods yield high quality VO2 with a three-order-of-magnitude transition.

FWP executive summaries, Basic Energy Sciences Materials Sciences Programs (SNL/NM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samara, G.A.

1997-05-01

The BES Materials Sciences Program has the central theme of Scientifically Tailored Materials. The major objective of this program is to combine Sandia`s expertise and capabilities in the areas of solid state sciences, advanced atomic-level diagnostics and materials synthesis and processing science to produce new classes of tailored materials as well as to enhance the properties of existing materials for US energy applications and for critical defense needs. Current core research in this program includes the physics and chemistry of ceramics synthesis and processing, the use of energetic particles for the synthesis and study of materials, tailored surfaces and interfacesmore » for materials applications, chemical vapor deposition sciences, artificially-structured semiconductor materials science, advanced growth techniques for improved semiconductor structures, transport in unconventional solids, atomic-level science of interfacial adhesion, high-temperature superconductors, and the synthesis and processing of nano-size clusters for energy applications. In addition, the program includes the following three smaller efforts initiated in the past two years: (1) Wetting and Flow of Liquid Metals and Amorphous Ceramics at Solid Interfaces, (2) Field-Structured Anisotropic Composites, and (3) Composition-Modulated Semiconductor Structures for Photovoltaic and Optical Technologies. The latter is a joint effort with the National Renewable Energy Laboratory. Separate summaries are given of individual research areas.« less

Guided neuronal growth on arrays of biofunctionalized GaAs/InGaAs semiconductor microtubes

NASA Astrophysics Data System (ADS)

Bausch, Cornelius S.; Koitmäe, Aune; Stava, Eric; Price, Amanda; Resto, Pedro J.; Huang, Yu; Sonnenberg, David; Stark, Yuliya; Heyn, Christian; Williams, Justin C.; Dent, Erik W.; Blick, Robert H.

2013-10-01

We demonstrate embedded growth of cortical mouse neurons in dense arrays of semiconductor microtubes. The microtubes, fabricated from a strained GaAs/InGaAs heterostructure, guide axon growth through them and potentially enable electrical and optical probing of propagating action potentials. The coaxial nature of the microtubes—similar to myelin—is expected to enhance the signal transduction along the axon. We present a technique of suppressing arsenic toxicity and prove the success of this technique by overgrowing neuronal mouse cells.

Process Challenges in Compound Semiconductors.

DTIC Science & Technology

1988-08-01

dielectric films , and metallization. It became evident during this examination that a major obstacle to the affordable, high-yield manufacture of...in surrounding regions. In both of the structures shown, the curvature of the layers is the characteristic solidification from solution in LPE ...pseudomorphic epitaxial growth is possible only with very thin films in which the structure is strained to match the lattice parameter of the

The effects of Peltier marking on semiconductor growth in a magnetic field

NASA Astrophysics Data System (ADS)

Sellers, Cheryl Casper

This research represents a model for three dimensional semiconductor growth in a vertical Bridgman process within an externally applied magnetic field with the additional effects of Peltier marking. The magnetic field is strong enough that inertial effects can be neglected and that viscous effects are confined to boundary layers. The objective of this research is a first step in the development of a method to accurately predict the distribution of dopants and species in the melt after a current pulse with a given duration and strength, with a given magnetic field and with a given crystal-melt interface shape. The first model involves an asymptotic solution to provide physical clarification of the flow. In both models the crystal/melt interface is modeled as fr=3r2 where 3≪1 . The first model incorporates a variable, a which ranges from 0.25 to 1.0. The second model involves an analytical solution with an arbitrary Ha and a≪1 . These models show the how the azimuthal velocity varies with increasing Ha and how the stream function varies in the meridional problem. This gives insight into how the dopant is mixed during the crystal growth process. The results demonstrate that current pulses with relatively weak magnetic fields and modest interface curvature can lead to very strong mixing in the melt.

Use of space ultra-vacuum for high quality semiconductor thin film growth

NASA Technical Reports Server (NTRS)

Ignatiev, A.; Sterling, M.; Sega, R. M.

1992-01-01

The utilization of space for materials processing is being expanded through a unique concept of epitaxial thin film growth in the ultra-vacuum of low earth orbit (LEO). This condition can be created in the wake of an orbiting space vehicle; and assuming that the vehicle itself does not pertub the environment, vacuum levels of better than 10 exp -14 torr can be attained. This vacuum environment has the capacity of greatly enhancing epitaxial thin film growth and will be the focus of experiments conducted aboard the Wake Shield Facility (WSF) currently being developed by the Space Vacuum Epitaxy Center (SVEC), Industry, and NASA.

A proposal for epitaxial thin film growth in outer space

NASA Technical Reports Server (NTRS)

Ignatiev, Alex; Chu, C. W.

1988-01-01

A new concept for materials processing in space exploits the ultravacuum component of space for thin film epitaxial growth. The unique low earth orbit space environment is expected to yield 10 to the -14th torr or better pressures, semiinfinite pumping speeds, and large ultravacuum volume without walls. These space ultravacuum properties promise major improvement in the quality, unique nature, and the throughput of epitaxially grown materials. Advanced thin film materials to be epitaxially grown in space include semiconductors, magnetic materials, and thin film high temperature superconductors.

Atomistic Interface Dynamics in Sn-Catalyzed Growth of Wurtzite and Zinc-Blende ZnO Nanowires.

PubMed

Jia, Shuangfeng; Hu, Shuaishuai; Zheng, He; Wei, Yanjie; Meng, Shuang; Sheng, Huaping; Liu, Huihui; Zhou, Siyuan; Zhao, Dongshan; Wang, Jianbo

2018-06-11

Unraveling the phase selection mechanisms of semiconductor nanowires (NWs) is critical for the applications in future advanced nanodevices. In this study, the atomistic vapor-solid-liquid growth processes of Sn-catalyzed wurtzite (WZ) and zinc blende (ZB) ZnO are directly revealed based on the in situ transmission electron microscopy. The growth kinetics of WZ and ZB crystal phases in ZnO appear markedly different in terms of the NW-droplet interface, whereas the nucleation site as determined by the contact angle ϕ between the seed particle and the NW is found to be crucial for tuning the NW structure through combined experimental and theoretical investigations. These results offer an atomic-scale view into the dynamic growth process of ZnO NW, which has implications for the phase-controllable synthesis of II-VI compounds and heterostructures with tunable band structures.

Formation of nanotwin networks during high-temperature crystallization of amorphous germanium

DOE PAGES

Sandoval, Luis; Reina, Celia; Marian, Jaime

2015-11-26

Germanium is an extremely important material used for numerous functional applications in many fields of nanotechnology. In this paper, we study the crystallization of amorphous Ge using atomistic simulations of critical nano-metric nuclei at high temperatures. We find that crystallization occurs by the recurrent transfer of atoms via a diffusive process from the amorphous phase into suitably-oriented crystalline layers. We accompany our simulations with a comprehensive thermodynamic and kinetic analysis of the growth process, which explains the energy balance and the interfacial growth velocities governing grain growth. For the <111> crystallographic orientation, we find a degenerate atomic rearrangement process, withmore » two zero-energy modes corresponding to a perfect crystalline structure and the formation of a Σ3 twin boundary. Continued growth in this direction results in the development a twin network, in contrast with all other growth orientations, where the crystal grows defect-free. This particular mechanism of crystallization from amorphous phases is also observed during solid-phase epitaxial growth of <111> semiconductor crystals, where growth is restrained to one dimension. Lastly, we calculate the equivalent X-ray diffraction pattern of the obtained nanotwin networks, providing grounds for experimental validation.« less

Formation of Nanotwin Networks during High-Temperature Crystallization of Amorphous Germanium

PubMed Central

Sandoval, Luis; Reina, Celia; Marian, Jaime

2015-01-01

Germanium is an extremely important material used for numerous functional applications in many fields of nanotechnology. In this paper, we study the crystallization of amorphous Ge using atomistic simulations of critical nano-metric nuclei at high temperatures. We find that crystallization occurs by the recurrent transfer of atoms via a diffusive process from the amorphous phase into suitably-oriented crystalline layers. We accompany our simulations with a comprehensive thermodynamic and kinetic analysis of the growth process, which explains the energy balance and the interfacial growth velocities governing grain growth. For the 〈111〉 crystallographic orientation, we find a degenerate atomic rearrangement process, with two zero-energy modes corresponding to a perfect crystalline structure and the formation of a Σ3 twin boundary. Continued growth in this direction results in the development a twin network, in contrast with all other growth orientations, where the crystal grows defect-free. This particular mechanism of crystallization from amorphous phases is also observed during solid-phase epitaxial growth of 〈111〉 semiconductor crystals, where growth is restrained to one dimension. We calculate the equivalent X-ray diffraction pattern of the obtained nanotwin networks, providing grounds for experimental validation. PMID:26607496

Space - A unique environment for process modeling R&D

NASA Technical Reports Server (NTRS)

Overfelt, Tony

1991-01-01

Process modeling, the application of advanced computational techniques to simulate real processes as they occur in regular use, e.g., welding, casting and semiconductor crystal growth, is discussed. Using the low-gravity environment of space will accelerate the technical validation of the procedures and enable extremely accurate determinations of the many necessary thermophysical properties. Attention is given to NASA's centers for the commercial development of space; joint ventures of universities, industries, and goverment agencies to study the unique attributes of space that offer potential for applied R&D and eventual commercial exploitation.

Power Electronic Semiconductor Materials for Automotive and Energy Saving Applications - SiC, GaN, Ga2O3, and Diamond.

PubMed

Wellmann, Peter J

2017-11-17

Power electronics belongs to the future key technologies in order to increase system efficiency as well as performance in automotive and energy saving applications. Silicon is the major material for electronic switches since decades. Advanced fabrication processes and sophisticated electronic device designs have optimized the silicon electronic device performance almost to their theoretical limit. Therefore, to increase the system performance, new materials that exhibit physical and chemical properties beyond silicon need to be explored. A number of wide bandgap semiconductors like silicon carbide, gallium nitride, gallium oxide, and diamond exhibit outstanding characteristics that may pave the way to new performance levels. The review will introduce these materials by (i) highlighting their properties, (ii) introducing the challenges in materials growth, and (iii) outlining limits that need innovation steps in materials processing to outperform current technologies.

Power Electronic Semiconductor Materials for Automotive and Energy Saving Applications – SiC, GaN, Ga2O3, and Diamond

PubMed Central

2017-01-01

Power electronics belongs to the future key technologies in order to increase system efficiency as well as performance in automotive and energy saving applications. Silicon is the major material for electronic switches since decades. Advanced fabrication processes and sophisticated electronic device designs have optimized the silicon electronic device performance almost to their theoretical limit. Therefore, to increase the system performance, new materials that exhibit physical and chemical properties beyond silicon need to be explored. A number of wide bandgap semiconductors like silicon carbide, gallium nitride, gallium oxide, and diamond exhibit outstanding characteristics that may pave the way to new performance levels. The review will introduce these materials by (i) highlighting their properties, (ii) introducing the challenges in materials growth, and (iii) outlining limits that need innovation steps in materials processing to outperform current technologies. PMID:29200530

MBE Growth of Ferromagnetic Metal/Compound Semiconductor Heterostructures for Spintronics

ScienceCinema

Palmstrom, Chris [University of California, Santa Barbara, California, United States

2017-12-09

Electrical transport and spin-dependent transport across ferromagnet/semiconductor contacts is crucial in the realization of spintronic devices. Interfacial reactions, the formation of non-magnetic interlayers, and conductivity mismatch have been attributed to low spin injection efficiency. MBE has been used to grow epitaxial ferromagnetic metal/GA(1-x)AL(x)As heterostructures with the aim of controlling the interfacial structural, electronic, and magnetic properties. In situ, STM, XPS, RHEED and LEED, and ex situ XRD, RBS, TEM, magnetotransport, and magnetic characterization have been used to develop ferromagnetic elemental and metallic compound/compound semiconductor tunneling contacts for spin injection. The efficiency of the spin polarized current injected from the ferromagnetic contact has been determined by measuring the electroluminescence polarization of the light emitted from/GA(1-x)AL(x)As light-emitting diodes as a function of applied magnetic field and temperature. Interfacial reactions during MBE growth and post-growth anneal, as well as the semiconductor device band structure, were found to have a dramatic influence on the measured spin injection, including sign reversal. Lateral spin-transport devices with epitaxial ferromagnetic metal source and drain tunnel barrier contacts have been fabricated with the demonstration of electrical detection and the bias dependence of spin-polarized electron injection and accumulation at the contacts. This talk emphasizes the progress and achievements in the epitaxial growth of a number of ferromagnetic compounds/III-V semiconductor heterostructures and the progress towards spintronic devices.

Kinetic Monte Carlo simulation of intermixing during semiconductor heteroepitaxy

NASA Astrophysics Data System (ADS)

Rouhani, M. Djafari; Kassem, H.; Dalla Torre, J.; Landa, G.; Estève, D.

2002-03-01

We have used the kinetic Monte Carlo technique to investigate the intermixing mechanisms during the heteroepitaxial growth of semiconductors. We have shown that the temperature increases the intermixing between the substrate and deposited film, while an increasing growth rate inhibits this intermixing. We have also observed that intermixing is reduced when the energetics becomes unfavorable, i.e. with high lattice mismatches or hard-deposited materials.

Feasibilty analyses of electroepitaxial research and development accommodations. Volume 2: Electroepitaxial growth of GaAs

NASA Technical Reports Server (NTRS)

1982-01-01

The technique of electromigration, i.e., electric field induced forced convection, can be used to grow semiconductor material and other compounds from solution by passing electric current through the growth interface while the temperature of the system is maintained constant. Current controlled electromigration, referred to as electroepitaxy, was successfully applied to grow epitaxial layers of various semiconductors and garnets.

Epitaxy of semiconductor-superconductor nanowires

NASA Astrophysics Data System (ADS)

Krogstrup, P.; Ziino, N. L. B.; Chang, W.; Albrecht, S. M.; Madsen, M. H.; Johnson, E.; Nygård, J.; Marcus, C. M.; Jespersen, T. S.

2015-04-01

Controlling the properties of semiconductor/metal interfaces is a powerful method for designing functionality and improving the performance of electrical devices. Recently semiconductor/superconductor hybrids have appeared as an important example where the atomic scale uniformity of the interface plays a key role in determining the quality of the induced superconducting gap. Here we present epitaxial growth of semiconductor-metal core-shell nanowires by molecular beam epitaxy, a method that provides a conceptually new route to controlled electrical contacting of nanostructures and the design of devices for specialized applications such as topological and gate-controlled superconducting electronics. Our materials of choice, InAs/Al grown with epitaxially matched single-plane interfaces, and alternative semiconductor/metal combinations allowing epitaxial interface matching in nanowires are discussed. We formulate the grain growth kinetics of the metal phase in general terms of continuum parameters and bicrystal symmetries. The method realizes the ultimate limit of uniform interfaces and seems to solve the soft-gap problem in superconducting hybrid structures.

Atomic-order thermal nitridation of group IV semiconductors for ultra-large-scale integration

NASA Astrophysics Data System (ADS)

Murota, Junichi; Le Thanh, Vinh

2015-03-01

One of the main requirements for ultra-large-scale integration (ULSI) is atomic-order control of process technology. Our concept of atomically controlled processing for group IV semiconductors is based on atomic-order surface reaction control in Si-based CVD epitaxial growth. On the atomic-order surface nitridation of a few nm-thick Ge/about 4 nm-thick Si0.5Ge0.5/Si(100) by NH3, it is found that N atoms diffuse through nm-order thick Ge layer into Si0.5Ge0.5/Si(100) substrate and form Si nitride, even at 500 °C. By subsequent H2 heat treatment, although N atomic amount in Ge layer is reduced drastically, the reduction of the Si nitride is slight. It is suggested that N diffusion in Ge layer is suppressed by the formation of Si nitride and that Ge/atomic-order N layer/Si1-xGex/Si (100) heterostructure is formed. These results demonstrate the capability of CVD technology for atomically controlled nitridation of group IV semiconductors for ultra-large-scale integration. Invited talk at the 7th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2014, 2-6 November, 2014, Ha Long, Vietnam.

Alberi Validates New Theory, Sheds Light on Semiconductors | News | NREL

Science.gov Websites

the discovery when they found that light can suppress native defect formation during semiconductor growth. When Alberi and Scarpulla began discussing the concept of how light can affect semiconductor that pieces easily fit together, so are the atoms in the crystal. But when an atom appears in a crystal

Polycrystalline semiconductor processing

DOEpatents

Glaeser, Andreas M.; Haggerty, John S.; Danforth, Stephen C.

1983-01-01

A process for forming large-grain polycrystalline films from amorphous films for use as photovoltaic devices. The process operates on the amorphous film and uses the driving force inherent to the transition from the amorphous state to the crystalline state as the force which drives the grain growth process. The resultant polycrystalline film is characterized by a grain size that is greater than the thickness of the film. A thin amorphous film is deposited on a substrate. The formation of a plurality of crystalline embryos is induced in the amorphous film at predetermined spaced apart locations and nucleation is inhibited elsewhere in the film. The crystalline embryos are caused to grow in the amorphous film, without further nucleation occurring in the film, until the growth of the embryos is halted by imgingement on adjacently growing embryos. The process is applicable to both batch and continuous processing techniques. In either type of process, the thin amorphous film is sequentially doped with p and n type dopants. Doping is effected either before or after the formation and growth of the crystalline embryos in the amorphous film, or during a continuously proceeding crystallization step.

Polycrystalline semiconductor processing

DOEpatents

Glaeser, A.M.; Haggerty, J.S.; Danforth, S.C.

1983-04-05

A process is described for forming large-grain polycrystalline films from amorphous films for use as photovoltaic devices. The process operates on the amorphous film and uses the driving force inherent to the transition from the amorphous state to the crystalline state as the force which drives the grain growth process. The resultant polycrystalline film is characterized by a grain size that is greater than the thickness of the film. A thin amorphous film is deposited on a substrate. The formation of a plurality of crystalline embryos is induced in the amorphous film at predetermined spaced apart locations and nucleation is inhibited elsewhere in the film. The crystalline embryos are caused to grow in the amorphous film, without further nucleation occurring in the film, until the growth of the embryos is halted by impingement on adjacently growing embryos. The process is applicable to both batch and continuous processing techniques. In either type of process, the thin amorphous film is sequentially doped with p and n type dopants. Doping is effected either before or after the formation and growth of the crystalline embryos in the amorphous film, or during a continuously proceeding crystallization step. 10 figs.

Characterization of solar-grade silicon produced by the SiF4-Na process

NASA Technical Reports Server (NTRS)

Sanjurjo, A.; Sancier, K. M.; Emerson, R. M.; Leach, S. C.; Minahan, J.

1986-01-01

A process was developed for producing low cost solar grade silicon by the reaction between SiF4 gas and sodium metal. The results of the characterization of the silicon are presented. These results include impurity levels, electronic properties of the silicon after crystal growth, and the performance of solar photovoltaic cells fabricated from wafers of the single crystals. The efficiency of the solar cells fabricated from semiconductor silicon and SiF4-Na silicon was the same.

All Ultra-High Vacuum In-Situ Growth & Processing Approaches to Realization of Semiconductor Nanostructure Arrays

DTIC Science & Technology

1997-05-15

Quantum Box/Dot, Strained Epitaxy , 3D islands, Patterned Substrates, Molecular Beam Epitaxy Focused Ion Beam , In-Situ Processing, Quantum Box Lasers...Grown on Planar and Patterned GaAs(100) Substrates by Molecular Beam Epitaxy ", J. Vac. Sei. Technol. B13, 642(1995) 5. A. Madhukar, P. Chen, Q. Xie...Formation and Vertical Self-Organization on GaAs(lOO) via Molecular Beam Epitaxy ", Paper presented at MRS Spring 󈨣 Meeting (Apr. 17-21, 1995, San

Epitaxial growth of 100-μm thick M-type hexaferrite crystals on wide bandgap semiconductor GaN/Al{sub 2}O{sub 3} substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Bolin; Su, Zhijuan; Bennett, Steve

2014-05-07

Thick barium hexaferrite BaFe{sub 12}O{sub 19} (BaM) films having thicknesses of ∼100 μm were epitaxially grown on GaN/Al{sub 2}O{sub 3} substrates from a molten-salt solution by vaporizing the solvent. X-ray diffraction measurement verified the growth of BaM (001) textured growth of thick films. Saturation magnetization, 4πM{sub s}, was measured for as-grown films to be 4.6 ± 0.2 kG and ferromagnetic resonance measurements revealed a microwave linewidth of ∼100 Oe at X-band. Scanning electron microscopy indicated clear hexagonal crystals distributed on the semiconductor substrate. These results demonstrate feasibility of growing M-type hexaferrite crystal films on wide bandgap semiconductor substrates by using a simplemore » powder melting method. It also presents a potential pathway for the integration of ferrite microwave passive devices with active semiconductor circuit elements creating system-on-a-wafer architectures.« less

Strain-engineered growth of two-dimensional materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahn, Geun Ho; Amani, Matin; Rasool, Haider

The application of strain to semiconductors allows for controlled modification of their band structure. This principle is employed for the manufacturing of devices ranging from high-performance transistors to solid-state lasers. Traditionally, strain is typically achieved via growth on lattice-mismatched substrates. For two-dimensional (2D) semiconductors, this is not feasible as they typically do not interact epitaxially with the substrate. Here in this paper, we demonstrate controlled strain engineering of 2D semiconductors during synthesis by utilizing the thermal coefficient of expansion mismatch between the substrate and semiconductor. Using WSe 2 as a model system, we demonstrate stable built-in strains ranging from 1%more » tensile to 0.2% compressive on substrates with different thermal coefficient of expansion. Consequently, we observe a dramatic modulation of the band structure, manifested by a strain-driven indirect-to-direct bandgap transition and brightening of the dark exciton in bilayer and monolayer WSe 2, respectively. The growth method developed here should enable flexibility in design of more sophisticated devices based on 2D materials.« less

Strain-engineered growth of two-dimensional materials

DOE PAGES

Ahn, Geun Ho; Amani, Matin; Rasool, Haider; ...

2017-09-20

The application of strain to semiconductors allows for controlled modification of their band structure. This principle is employed for the manufacturing of devices ranging from high-performance transistors to solid-state lasers. Traditionally, strain is typically achieved via growth on lattice-mismatched substrates. For two-dimensional (2D) semiconductors, this is not feasible as they typically do not interact epitaxially with the substrate. Here in this paper, we demonstrate controlled strain engineering of 2D semiconductors during synthesis by utilizing the thermal coefficient of expansion mismatch between the substrate and semiconductor. Using WSe 2 as a model system, we demonstrate stable built-in strains ranging from 1%more » tensile to 0.2% compressive on substrates with different thermal coefficient of expansion. Consequently, we observe a dramatic modulation of the band structure, manifested by a strain-driven indirect-to-direct bandgap transition and brightening of the dark exciton in bilayer and monolayer WSe 2, respectively. The growth method developed here should enable flexibility in design of more sophisticated devices based on 2D materials.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Virginia R.; Nepal, Neeraj; Johnson, Scooter D.

Wide bandgap semiconducting nitrides have found wide-spread application as light emitting and laser diodes and are under investigation for further application in optoelectronics, photovoltaics, and efficient power switching technologies. Alloys of the binary semiconductors allow adjustments of the band gap, an important semiconductor material characteristic, which is 6.2 eV for aluminum nitride (AlN), 3.4 eV for gallium nitride, and 0.7 eV for (InN). Currently, the highest quality III-nitride films are deposited by metalorganic chemical vapor deposition and molecular beam epitaxy. Temperatures of 900 °C and higher are required to deposit high quality AlN. Research into depositing III-nitrides with atomic layermore » epitaxy (ALEp) is ongoing because it is a fabrication friendly technique allowing lower growth temperatures. Because it is a relatively new technique, there is insufficient understanding of the ALEp growth mechanism which will be essential to development of the process. Here, grazing incidence small angle x-ray scattering is employed to observe the evolving behavior of the surface morphology during growth of AlN by ALEp at temperatures from 360 to 480 °C. Increased temperatures of AlN resulted in lower impurities and relatively fewer features with short range correlations.« less

TaC-coated graphite prepared via a wet ceramic process: Application to CVD susceptors for epitaxial growth of wide-bandgap semiconductors

NASA Astrophysics Data System (ADS)

Nakamura, Daisuke; Kimura, Taishi; Narita, Tetsuo; Suzumura, Akitoshi; Kimoto, Tsunenobu; Nakashima, Kenji

2017-11-01

A novel sintered tantalum carbide coating (SinTaC) prepared via a wet ceramic process is proposed as an approach to reducing the production cost and improving the crystal quality of bulk-grown crystals and epitaxially grown films of wide-bandgap semiconductors. Here, we verify the applicability of the SinTaC components as susceptors for chemical vapor deposition (CVD)-SiC and metal-organic chemical vapor deposition (MOCVD)-GaN epitaxial growth in terms of impurity incorporation from the SinTaC layers and also clarify the surface-roughness controllability of SinTaC layers and its advantage in CVD applications. The residual impurity elements in the SinTaC layers were confirmed to not severely incorporate into the CVD-SiC and MOCVD-GaN epilayers grown using the SinTaC susceptors. The quality of the epilayers was also confirmed to be equivalent to that of epilayers grown using conventional susceptors. Furthermore, the surface roughness of the SinTaC components was controllable over a wide range of average roughness (0.4 ≤ Ra ≤ 5 μm) and maximum height roughness (3 ≤ Rz ≤ 36 μm) through simple additional surface treatment procedures, and the surface-roughened SinTaC susceptor fabricated using these procedures was predicted to effectively reduce thermal stress on epi-wafers. These results confirm that SinTaC susceptors are applicable to epitaxial growth processes and are advantageous over conventional susceptor materials for reducing the epi-cost and improving the quality of epi-wafers.

Overcoming Limitations in Semiconductor Alloy Design

NASA Astrophysics Data System (ADS)

Christian, Theresa Marie

Inorganic semiconductors provide an astonishingly versatile, robust, and efficient platform for optoelectronic energy conversion devices. However, conventional alloys and growth regimes face materials challenges that restrict the full potential of these devices. Novel alloy designs based on isoelectronic co-doping, metamorphic growth and controllable atomic ordering offer new pathways to practical and ultra-high-efficiency optoelectronic devices including solar cells and light-emitting diodes. Abnormal isoelectronic alloys of GaP1-xBix, GaP 1-x-yBixNy, and GaAs1-xBix with unprecedented bismuth incorporation fractions and crystalline quality are explored in this thesis research. Comparative studies of several GaP1-xBix and GaP1-x-yBixNy alloys demonstrate that the site-specific incorporation of bismuth during epitaxial growth is sensitive to growth temperature and has dramatic effects on carrier transfer processes in these alloys. Additionally, distinctive bismuth-related localized states are spectrally identified for the first time in samples of GaAs1-xBix grown by laser-assisted epitaxial growth. These results address fundamental questions about the nature of bismuth-bismuth inter-impurity interactions. Finally, a metamorphic growth strategy for a novel light-emitting diode (LED) design is also discussed. This work utilized direct-bandgap AlxIn1-xP active layers with atomic ordering-based electron confinement to improve emission in the yellow and green spectral regions, where incumbent technologies are least effective, and demonstrated the feasibility of non-lattice-matched LED active materials for visible light emission.

Joint Services Electronics Program.

DTIC Science & Technology

1987-10-15

semiconductor perturb the index of refraction which can be detected in a Nomarski -type optical interferometer. For example, we have demonstrated the real-time...probe relies on a different physical effect and operates by interferometrically detecting the phase change induced in an optical beam by the presence of... interferometric diameter measurement system to monitor the growth process, has been in operation for . several years. The focussing optics and pulling mechanisms

Method For Growth of Crystal Surfaces and Growth of Heteroepitaxial Single Crystal Films Thereon

NASA Technical Reports Server (NTRS)

Powell, J. Anthony (Inventor); Larkin, David J. (Inventor); Neudeck, Philip G. (Inventor); Matus, Lawrence G. (Inventor)

2000-01-01

A method of growing atomically-flat surfaces and high quality low-defect crystal films of semiconductor materials and fabricating improved devices thereon is discussed. The method is also suitable for growing films heteroepitaxially on substrates that are different than the film. The method is particularly suited for growth of elemental semiconductors (such as Si), compounds of Groups III and V elements of the Periodic Table (such as GaN), and compounds and alloys of Group IV elements of the Periodic Table (such as SiC).

Zone leveling and solution growth of complex compound semiconductors in space

NASA Technical Reports Server (NTRS)

Bachmann, K. J.

1986-01-01

A research program on complex semiconducting compounds and alloys was completed that addressed the growth of single crystals of CdSe(y)Te(1-y), Zn(x)Cd(1-x)Te, Mn(x)Cd(1-x)Te, InP(y)As(1-y) and CuInSe2 and the measurement of fundamental physico-chemical properties characterizing the above materials. The purpose of this ground based research program was to lay the foundations for further research concerning the growth of complex ternary compound semiconductors in a microgravity environment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elimelech, Orian; Liu, Jing; Plonka, Anna M.

Doping of nanocrystals (NCs) is a key, yet underexplored, approach for tuning of the electronic properties of semiconductors. An important route for doping of NCs is by vacancy formation. The size and concentration dependence of doping was studied in copper(I) sulfide (Cu2S) NCs through a redox reaction with iodine molecules (I2), which formed vacancies accompanied by a localized surface plasmon response. X-ray spectroscopy and diffraction reveal transformation from Cu2S to Cu-depleted phases, along with CuI formation. Greater reaction efficiency was observed for larger NCs. This behavior is attributed to interplay of the vacancy formation energy, which decreases for smaller sizedmore » NCs, and the growth of CuI on the NC surface, which is favored on well-defined facets of larger NCs. This doping process allows tuning of the plasmonic properties of a semiconductor across a wide range of plasmonic frequencies by varying the size of NCs and the concentration of iodine. Controlled vacancy doping of NCs may be used to tune and tailor semiconductors for use in optoelectronic applications.« less

Quasi-Phase Diagrams at Air/Oil Interfaces and Bulk Oil Phases for Crystallization of Small-Molecular Semiconductors by Adjusting Gibbs Adsorption.

PubMed

Watanabe, Satoshi; Ohta, Takahisa; Urata, Ryota; Sato, Tetsuya; Takaishi, Kazuto; Uchiyama, Masanobu; Aoyama, Tetsuya; Kunitake, Masashi

2017-09-12

The temperature and concentration dependencies of the crystallization of two small-molecular semiconductors were clarified by constructing quasi-phase diagrams at air/oil interfaces and in bulk oil phases. A quinoidal quaterthiophene derivative with four alkyl chains (QQT(CN)4) in 1,1,2,2-tetrachroloethane (TCE) and a thienoacene derivative with two alkyl chains (C8-BTBT) in o-dichlorobenzene were used. The apparent crystal nucleation temperature (T n ) and dissolution temperature (T d ) of the molecules were determined based on optical microscopy examination in closed glass capillaries and open dishes during slow cooling and heating processes, respectively. T n and T d were considered estimates of the critical temperatures for nuclear formation and crystal growth, respectively. The T n values of QQT(CN)4 and C8-BTBT at the air/oil interfaces were higher than those in the bulk oil phases, whereas the T d values at the air/oil interfaces were almost the same as those in the bulk oil phases. These Gibbs adsorption phenomena were attributed to the solvophobic effect of the alkyl chain moieties. The temperature range between T n and T d corresponds to suitable supercooling conditions for ideal crystal growth based on the suppression of nucleation. The T n values at the water/oil and oil/glass interfaces did not shift compared with those of the bulk phases, indicating that adsorption did not occur at the hydrophilic interfaces. Promotion and inhibition of nuclear formation for crystal growth of the semiconductors were achieved at the air/oil and hydrophilic interfaces, respectively.

Defect Characterization, Imaging, and Control in Wide-Bandgap Semiconductors and Devices

NASA Astrophysics Data System (ADS)

Brillson, L. J.; Foster, G. M.; Cox, J.; Ruane, W. T.; Jarjour, A. B.; Gao, H.; von Wenckstern, H.; Grundmann, M.; Wang, B.; Look, D. C.; Hyland, A.; Allen, M. W.

2018-03-01

Wide-bandgap semiconductors are now leading the way to new physical phenomena and device applications at nanoscale dimensions. The impact of defects on the electronic properties of these materials increases as their size decreases, motivating new techniques to characterize and begin to control these electronic states. Leading these advances have been the semiconductors ZnO, GaN, and related materials. This paper highlights the importance of native point defects in these semiconductors and describes how a complement of spatially localized surface science and spectroscopy techniques in three dimensions can characterize, image, and begin to control these electronic states at the nanoscale. A combination of characterization techniques including depth-resolved cathodoluminescence spectroscopy, surface photovoltage spectroscopy, and hyperspectral imaging can describe the nature and distribution of defects at interfaces at both bulk and nanoscale surfaces, their metal interfaces, and inside nanostructures themselves. These features as well as temperature and mechanical strain inside wide-bandgap device structures at the nanoscale can be measured even while these devices are operating. These advanced capabilities enable several new directions for describing defects at the nanoscale, showing how they contribute to device degradation, and guiding growth processes to control them.

The 3-5 semiconductor solid solution single crystal growth. [low gravity float zone growth experiments using gallium indium antimonides and cadmium tellurides

NASA Technical Reports Server (NTRS)

Gertner, E. R.

1980-01-01

Techniques used for liquid and vapor phase epitaxy of gallium indium arsenide are described and the difficulties encountered are examined. Results show that the growth of bulk III-V solid solution single crystals in a low gravity environment will not have a major technological impact. The float zone technique in a low gravity environment is demonstrated using cadmium telluride. It is shown that this approach can result in the synthesis of a class of semiconductors that can not be grown in normal gravity because of growth problems rooted in the nature of their phase diagrams.

Lattice matched semiconductor growth on crystalline metallic substrates

DOEpatents

Norman, Andrew G; Ptak, Aaron J; McMahon, William E

2013-11-05

Methods of fabricating a semiconductor layer or device and said devices are disclosed. The methods include but are not limited to providing a metal or metal alloy substrate having a crystalline surface with a known lattice parameter (a). The methods further include growing a crystalline semiconductor alloy layer on the crystalline substrate surface by coincident site lattice matched epitaxy. The semiconductor layer may be grown without any buffer layer between the alloy and the crystalline surface of the substrate. The semiconductor alloy may be prepared to have a lattice parameter (a') that is related to the lattice parameter (a). The semiconductor alloy may further be prepared to have a selected band gap.

Method of making silicon on insalator material using oxygen implantation

DOEpatents

Hite, Larry R.; Houston, Ted; Matloubian, Mishel

1989-01-01

The described embodiments of the present invention provide a semiconductor on insulator structure providing a semiconductor layer less susceptible to single event upset errors (SEU) due to radiation. The semiconductor layer is formed by implanting ions which form an insulating layer beneath the surface of a crystalline semiconductor substrate. The remaining crystalline semiconductor layer above the insulating layer provides nucleation sites for forming a crystalline semiconductor layer above the insulating layer. The damage caused by implantation of the ions for forming an insulating layer is left unannealed before formation of the semiconductor layer by epitaxial growth. The epitaxial layer, thus formed, provides superior characteristics for prevention of SEU errors, in that the carrier lifetime within the epitaxial layer, thus formed, is less than the carrier lifetime in epitaxial layers formed on annealed material while providing adequate semiconductor characteristics.

Low-temperature plasma-deposited silicon epitaxial films: Growth and properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demaurex, Bénédicte, E-mail: benedicte.demaurex@epfl.ch; Bartlome, Richard; Seif, Johannes P.

2014-08-07

Low-temperature (≤200 °C) epitaxial growth yields precise thickness, doping, and thermal-budget control, which enables advanced-design semiconductor devices. In this paper, we use plasma-enhanced chemical vapor deposition to grow homo-epitaxial layers and study the different growth modes on crystalline silicon substrates. In particular, we determine the conditions leading to epitaxial growth in light of a model that depends only on the silane concentration in the plasma and the mean free path length of surface adatoms. For such growth, we show that the presence of a persistent defective interface layer between the crystalline silicon substrate and the epitaxial layer stems not only frommore » the growth conditions but also from unintentional contamination of the reactor. Based on our findings, we determine the plasma conditions to grow high-quality bulk epitaxial films and propose a two-step growth process to obtain device-grade material.« less

Morphology Controlled Fabrication of InN Nanowires on Brass Substrates

PubMed Central

Li, Huijie; Zhao, Guijuan; Wang, Lianshan; Chen, Zhen; Yang, Shaoyan

2016-01-01

Growth of semiconductor nanowires on cheap metal substrates could pave the way to the large-scale manufacture of low-cost nanowire-based devices. In this work, we demonstrated that high density InN nanowires can be directly grown on brass substrates by metal-organic chemical vapor deposition. It was found that Zn from the brass substrates is the key factor in the formation of nanowires by restricting the lateral growth of InN. The nanowire morphology is highly dependent on the growth temperature. While at a lower growth temperature, the nanowires and the In droplets have large diameters. At the elevated growth temperature, the lateral sizes of the nanowires and the In droplets are much smaller. Moreover, the nanowire diameter can be controlled in situ by varying the temperature in the growth process. This method is very instructive to the diameter-controlled growth of nanowires of other materials. PMID:28335323

Low-temperature plasma-deposited silicon epitaxial films: Growth and properties

DOE PAGES

Demaurex, Bénédicte; Bartlome, Richard; Seif, Johannes P.; ...

2014-08-05

Low-temperature (≤ 180 °C) epitaxial growth yields precise thickness, doping, and thermal-budget control, which enables advanced-design semiconductor devices. In this paper, we use plasma-ehanced chemical vapor deposition to grow homo-epitaxial layers and study the different growth modes on crystalline silicon substrates. In particular, we determine the conditions leading to epitaxial growth in light of a model that depends only on the silane concentration in the plasma and the mean free path length of surface adatoms. For such growth, we show that the presence of a persistent defective interface layer between the crystalline silicon substrate and the epitaxial layer stems notmore » only from the growth conditions but also from unintentional contamination of the reactor. As a result of our findings, we determine the plasma conditions to grow high-quality bulk epitaxial films and propose a two-step growth process to obtain device-grade material.« less

Growth of single-layer graphene on Ge (1 0 0) by chemical vapor deposition

NASA Astrophysics Data System (ADS)

Mendoza, C. D.; Caldas, P. G.; Freire, F. L.; Maia da Costa, M. E. H.

2018-07-01

The integration of graphene into nanoelectronic devices is dependent on the availability of direct deposition processes, which can provide uniform, large-area and high-quality graphene on semiconductor substrates such as Ge or Si. In this work, we synthesised graphene directly on p-type Ge (1 0 0) substrates by chemical vapour deposition. The influence of the CH4:H2 flow ratio on the graphene growth was investigated. Raman Spectroscopy, Raman mapping, Scanning Electron Microscopy, Atomic Force Microscopy and Scanning Tunnelling Microscopy/Scanning Tunnelling Spectroscopy results showed that good quality and homogeneous monolayer graphene over a large area can be achieved on Ge substrates directly with optimal growth conditions.

Chemical routes to nanocrystalline and thin-film III-VI and I-III-VI semiconductors

NASA Astrophysics Data System (ADS)

Hollingsworth, Jennifer Ann

1999-11-01

The work encompasses: (1) catalyzed low-temperature, solution-based routes to nano- and microcrystalline III-VI semiconductor powders and (2) spray chemical vapor deposition (spray CVD) of I-III-VI semiconductor thin films. Prior to this work, few, if any, examples existed of chemical catalysis applied to the synthesis of nonmolecular, covalent solids. New crystallization strategies employing catalysts were developed for the regioselective syntheses of orthorhombic InS (beta-InS), the thermodynamic phase, and rhombohedral InS (R-InS), a new, metastable structural isomer. Growth of beta-InS was facilitated by a solvent-suspended, molten-metal flux in a process similar to the SolutionLiquid-Solid (SLS) growth of InP and GaAs fibers and single-crystal whiskers. In contrast, metastable R-InS, having a pseudo-graphitic layered structure, was prepared selectively when the molecular catalyst, benzenethiol, was present in solution and the inorganic "catalyst" (metal flux) was not present. In the absence of any crystal-growth facilitator, metal flux or benzenethiol, amorphous product was obtained under the mild reaction conditions employed (T ≤ 203°C). The inorganic and organic catalysts permitted the regio-selective syntheses of InS and were also successfully applied to the growth of network and layered InxSey compounds, respectively, as well as nanocrystalline In2S3. Extensive microstructural characterization demonstrated that the layered compounds grew as fullerene-like nanostructures and large, colloidal single crystals. Films of the I-III-VI compounds, CuInS2, CuGaS2, and Cu(In,Ga)S 2, were deposited by spray CVD using the known single-source metalorganic precursor, (Ph3P)2CuIn(SEt)4, a new precursor, (Ph3P)2CuGa(SEt)3, and a mixture of the two precursors, respectively. The CulnS2 films exhibited a variety of microstructures from dense and faceted or platelet-like to porous and dendritic. Crystallographic orientations ranged from strongly [112] to strongly [220] oriented. Microstructure, orientation, and growth kinetics were controlled by changing processing parameters: carrier-gas flow rate, substrate temperature, and precursor-solution concentration. Low resistivities (<50 O cm) were associated with [220]-oriented films. All CuInS2 films were approximately stoichiometric and had the desired bandgap (Eg ≅ 1.4 eV) for application as the absorber layer in thin-film photovoltaic devices.

Direct Effect of Dielectric Surface Energy on Carrier Transport in Organic Field-Effect Transistors.

PubMed

Zhou, Shujun; Tang, Qingxin; Tian, Hongkun; Zhao, Xiaoli; Tong, Yanhong; Barlow, Stephen; Marder, Seth R; Liu, Yichun

2018-05-09

The understanding of the characteristics of gate dielectric that leads to optimized carrier transport remains controversial, and the conventional studies applied organic semiconductor thin films, which introduces the effect of dielectric on the growth of the deposited semiconductor thin films and hence only can explore the indirect effects. Here, we introduce pregrown organic single crystals to eliminate the indirect effect (semiconductor growth) in the conventional studies and to undertake an investigation of the direct effect of dielectric on carrier transport. It is shown that the matching of the polar and dispersive components of surface energy between semiconductor and dielectric is favorable for higher mobility. This new empirical finding may show the direct relationship between dielectric and carrier transport for the optimized mobility of organic field-effect transistors and hence show a promising potential for the development of next-generation high-performance organic electronic devices.

Carbon Nanotube based Nanotechnolgy

NASA Astrophysics Data System (ADS)

Meyyappan, M.

2000-10-01

Carbon nanotube(CNT) was discovered in the early 1990s and is an off-spring of C60(the fullerene or buckyball). CNT, depending on chirality and diameter, can be metallic or semiconductor and thus allows formation of metal-semiconductor and semiconductor-semiconductor junctions. CNT exhibits extraordinary electrical and mechanical properties and offers remarkable potential for revolutionary applications in electronics devices, computing and data storage technology, sensors, composites, storage of hydrogen or lithium for battery development, nanoelectromechanical systems(NEMS), and as tip in scanning probe microscopy(SPM) for imaging and nanolithography. Thus the CNT synthesis, characterization and applications touch upon all disciplines of science and engineering. A common growth method now is based on CVD though surface catalysis is key to synthesis, in contrast to many CVD applications common in microelectronics. A plasma based variation is gaining some attention. This talk will provide an overview of CNT properties, growth methods, applications, and research challenges and opportunities ahead.

KSC-97PC1382

NASA Image and Video Library

1997-09-08

United States Microgravity Payload-4 (USMP-4) experiments are prepared to be flown on Space Shuttle mission STS-87 in the Space Station Processing Facility at Kennedy Space Center (KSC). This horizontal tube is known as MEPHISTO, the French acronym for a cooperative American-French investigation of the fundamentals of crystal growth. This experiment, designed for the study of solidification (or freezing) during the growth cycle of liquid materials used for semiconductor crystals, aims to aid in the development of techniques for growing higher quality crystals on Earth. All STS-87 experiments are scheduled for launch on Nov. 19 from KSC

Synthesis of highly uniform Cu2O spheres by a two-step approach and their assembly to form photonic crystals with a brilliant color.

PubMed

Su, Xin; Chang, Jie; Wu, Suli; Tang, Bingtao; Zhang, Shufen

2016-03-21

Monodisperse semiconductor colloidal spheres with a high refractive index hold great potential for building photonic crystals with a strong band gap, but the difficulty in separating the nucleation and growth processes makes it challenging to prepare highly uniform semiconductor colloidal spheres. Herein, real monodisperse Cu2O spheres were prepared via a hot-injection & heating-up two-step method using diethylene glycol as a milder reducing agent. The diameter of the as prepared Cu2O spheres can be tuned from 90 nm to 190 nm precisely. The SEM images reveal that the obtained Cu2O spheres have a narrow size distribution, which permits their self-assembly to form photonic crystals. The effects of precursor concentration and heating rates on the size and morphology of the Cu2O spheres were investigated in detail. The results indicate that the key points of the method include the burst nucleation to form seeds at a high temperature followed by rapid cooling to prevent agglomeration, and appropriate precursor concentration as well as a moderate growth rate during the further growth process. Importantly, photonic crystal films exhibiting a brilliant structural color were fabricated with the obtained monodisperse Cu2O spheres as building blocks, proving the possibility of making photonic crystals with a strong band gap. The developed method was also successfully applied to prepare monodisperse CdS spheres with diameters in the range from 110 nm to 210 nm.

Surface chemistry relevant to material processing for semiconductor devices

NASA Astrophysics Data System (ADS)

Okada, Lynne Aiko

Metal-oxide-semiconductor (MOS) structures are the core of many modern integrated circuit (IC) devices. Each material utilized in the different regions of the device has its own unique chemistry. Silicon is the base semiconductor material used in the majority of these devices. With IC device complexity increasing and device dimensions decreasing, understanding material interactions and processing becomes increasingly critical. Hsb2 desorption is the rate-limiting step in silicon growth using silane under low temperature conditions. Activation energies for Hsb2 desorption measured during Si chemical vapor deposition (CVD) versus single-crystal studies are found to be significantly lower. It has been proposed that defect sites on the silicon surface could explain the observed differences. Isothermal Hsb2 desorption studies using laser induced thermal desorption (LITD) techniques have addressed this issue. The growth of low temperature oxides is another relevant issue for fabrication of IC devices. Recent studies using 1,4-disilabutane (DSB) (SiHsb3CHsb2CHsb2SiHsb3) at 100sp°C in ambient Osb2 displayed the successful low temperature growth of silicon dioxide (SiOsb2). However, these studies provided no information about the deposition mechanism. We performed LITD and Fourier transform infrared (FTIR) studies on single-crystal and porous silicon surfaces to examine the adsorption, decomposition, and desorption processes to determine the deposition mechanism. Titanium nitride (TiN) diffusion barriers are necessary in modern metallization structures. Controlled deposition using titanium tetrachloride (TiClsb4) and ammonia (NHsb3) has been demonstrated using atomic layered processing (ALP) techniques. We intended to study the sequential deposition method by monitoring the surface intermediates using LITD techniques. However, formation of a Cl impurity source, ammonium chloride (NHsb4sp+Clsp-), was observed, thereby, limiting our ability for effective studies. Tetrakis(dimethylamino)titanium (Tilbrack N\\{CHsb3\\}sb2rbracksb4) (TDMAT) is another precursor used in the CVD deposition of TiN films in IC devices. Thermal decomposition studies have demonstrated deviations from conformal deposition. Successful conformal deposition may be affected by readsorption of the reaction product, dimethylamine (HNlbrack CHsb3rbracksb2). Detailed studies were performed using LITD techniques in order to understand the adsorption and desorption kinetics of TDMAT and dimethylamine to gain insights about the conformal deposition of TiN.

Method for depositing high-quality microcrystalline semiconductor materials

DOEpatents

Guha, Subhendu [Bloomfield Hills, MI; Yang, Chi C [Troy, MI; Yan, Baojie [Rochester Hills, MI

2011-03-08

A process for the plasma deposition of a layer of a microcrystalline semiconductor material is carried out by energizing a process gas which includes a precursor of the semiconductor material and a diluent with electromagnetic energy so as to create a plasma therefrom. The plasma deposits a layer of the microcrystalline semiconductor material onto the substrate. The concentration of the diluent in the process gas is varied as a function of the thickness of the layer of microcrystalline semiconductor material which has been deposited. Also disclosed is the use of the process for the preparation of an N-I-P type photovoltaic device.

Shallow Melt Apparatus for Semicontinuous Czochralski Crystal Growth

DOEpatents

Wang, T.; Ciszek, T. F.

2006-01-10

In a single crystal pulling apparatus for providing a Czochralski crystal growth process, the improvement of a shallow melt crucible (20) to eliminate the necessity supplying a large quantity of feed stock materials that had to be preloaded in a deep crucible to grow a large ingot, comprising a gas tight container a crucible with a deepened periphery (25) to prevent snapping of a shallow melt and reduce turbulent melt convection; source supply means for adding source material to the semiconductor melt; a double barrier (23) to minimize heat transfer between the deepened periphery (25) and the shallow melt in the growth compartment; offset holes (24) in the double barrier (23) to increase melt travel length between the deepened periphery (25) and the shallow growth compartment; and the interface heater/heat sink (22) to control the interface shape and crystal growth rate.

Growth far from equilibrium: Examples from III-V semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuech, Thomas F.; Babcock, Susan E.; Mawst, Luke

The development of new applications has driven the field of materials design and synthesis to investigate materials that are not thermodynamically stable phases. Materials which are not thermodynamically stable can be synthesized and used in many applications. These materials are kinetically stabilized during use. The formation of such metastable materials requires both an understanding of the associated thermochemistry and the key surface transport processes present during growth. Phase separation is most easily accomplished at the growth surface during synthesis where mass transport is most rapid. These surface transport processes are sensitive to the surface stoichiometry, reconstruction, and chemistry as wellmore » as the growth temperature. The formation of new metastable semiconducting alloys with compositions deep within a compositional miscibility gap serves as model systems for the understanding of the surface chemical and physical processes controlling their formation. The GaAs{sub 1−y}Bi{sub y} system is used here to elucidate the role of surface chemistry in the formation of a homogeneous metastable composition during the chemical vapor deposition of the alloy system.« less

Magnetic damping of thermocapillary convection in the floating-zone growth of semiconductor crystals

NASA Astrophysics Data System (ADS)

Morthland, Timothy Edward

The floating zone is one process used to grow high purity semiconductor single crystals. In the floating-zone process, a liquid bridge of molten semiconductor, or melt, is held by surface tension between the upper, melting polycrystalline feed rod and the lower, solidifying single crystal. A perfect crystal would require a quiescent melt with pure diffusion of dopants during the entire period needed to grow the crystal. However, temperature variations along the free surface of the melt lead to gradients of the temperature-dependent surface tension, driving a strong and unsteady flow in the melt, commonly labeled thermocapillary or Marangoni convection. For small temperature differences along the free surface, unsteady thermocapillary convection occurs, disrupting the diffusion controlled solidification and creating undesirable dopant concentration variations in the semiconductor single crystal. Since molten semiconductors are good electrical conductors, an externally applied, steady magnetic field can eliminate the unsteadiness in the melt and can reduce the magnitude of the residual steady motion. Crystal growers hope that a strong enough magnetic field will lead to diffusion controlled solidification, but the magnetic field strengths needed to damp the unsteady thermocapillary convection as a function of floating-zone process parameters is unknown. This research has been conducted in the area of the magnetic damping of thermocapillary convection in floating zones. Both steady and unsteady flows have been investigated. Due to the added complexities in solving Maxwells equations in these magnetohydrodynamic problems and due to the thin boundary layers in these flows, a direct numerical simulation of the fluid and heat transfer in the floating zone is virtually impossible, and it is certainly impossible to run enough simulations to search for neutral stability as a function of magnetic field strength over the entire parameter space. To circumvent these difficulties, we have used matched asymptotic expansions, linear stability theory and numerics to characterize these flows. Some fundamental aspects of the heat transfer and fluid mechanics in these magnetohydrodynamic flows are elucidated in addition to the calculation of the magnetic field strengths required to damp unsteady thermocapillary convection as a function of process parameters.

Subeutectic Synthesis of Epitaxial Si-NWs with Diverse Catalysts Using a Novel Si Precursor

PubMed Central

2010-01-01

The applicability of a novel silicon precursor with respect to reasonable nanowire (NW) growth rates, feasibility of epitaxial NW growth and versatility with respect to diverse catalysts was investigated. Epitaxial growth of Si-NWs was achieved using octochlorotrisilane (OCTS) as Si precursor and Au as catalyst. In contrast to the synthesis approach with SiCl4 as precursor, OCTS provides Si without the addition of H2. By optimizing the growth conditions, effective NW synthesis is shown for alternative catalysts, in particular, Cu, Ag, Ni, and Pt with the latter two being compatible to complementary metal-oxide-semiconductor technology. As for these catalysts, the growth temperatures are lower than the lowest liquid eutectic; we suggest that the catalyst particle is in the solid state during NW growth and that a solid-phase diffusion process, either in the bulk, on the surface, or both, must be responsible for NW nucleation. PMID:20843058

Molecular-Beam Epitaxial Growth and Device Potential of Polar/Nonpolar Semiconductor Heterostructures.

DTIC Science & Technology

1985-06-24

research , and perhaps the most far-reaching one * A GaP -on-Si transistor was achieved, vastly better than any previous or concurrent effort towards this...the numerous conceptual and technological developments that had accumulated during the research . e) Defects in GaP -on-Si(211) Layers. With the help...Growth and Device Potential of Polar/Nonpolar Semiconductor Heterostructures Final Report by A Herbert Kroemer June 1985 -..2-- U. S. Army Research

Novel organic semiconductors and a high capacitance gate dielectric for organic thin film transistors

NASA Astrophysics Data System (ADS)

Cai, Xiuyu

2007-12-01

Organic semiconductors are attracting more and more interest as a promising set of materials in the field of electronics research. This thesis focused on several new organic semiconductors and a novel high-kappa dielectric thin film (SrTiO3), which are two essential parts in Organic Thin Film Transistors (OTFTs). Structure and morphology of thin films of tricyanovinyl capped oligothiophenes were studied using atomic force microscopy and x-ray diffraction. Thin film transistors of one compound exhibited a reasonable electron mobility of 0.02 cm2/Vs. Temperature dependent measurements on the thin film transistor based on this compound revealed shallow trap states that were interpreted in terms of a multiple trap and release model. Moreover, inversion of the majority charge carrier type from electrons to holes was observed when the number of oligothiophene rings increased to six and ambipolar transport behavior was observed for tricyanovinyl sexithiophene. Another interesting organic semiconductor compound is the fluoalkylquarterthiophene, which showed ambipolar transport and large hysteresis in the transfer curve. Due to the bistable state at floating gate, the thin film transistor was exploited to study non-volatile floating gate memory effects. The temperature dependence of the retention time for this memory device revealed that the electron trapping was an activated process. Following the earlier work on hybrid acene-thiophene organic semiconductors, new compounds with similar structure were studied to reveal the mechanism of the air-stability exhibited by some compounds. They all formed highly crystalline thin films and showed reasonable device performances which are well correlated with the molecular structures, thin film microstructures, and solid state packing. The most air-stable compound had no observable degradation with exposure to air for 15 months. SrTiO3 was developed to be employed in OTFTs. Optimization of thin film growth was performed using reactive sputtering growth. Excellent SrTiO3 epitaixal thin film growth was revealed on conductive SrTiO 3:Nb substrates. A maximum charge carrier density of 1014 cm-2 was obtained based on pentacene and perylene diimide thin film transistors. Some new physical phenomena, such as step-like transfer characteristic curve and negative transconductance, were observed at such high field effect induced charge carrier density.

The Application of Nano-TiO2 Photo Semiconductors in Agriculture

NASA Astrophysics Data System (ADS)

Wang, Yan; Sun, Changjiao; Zhao, Xiang; Cui, Bo; Zeng, Zhanghua; Wang, Anqi; Liu, Guoqiang; Cui, Haixin

2016-11-01

Nanometer-sized titanium dioxide (TiO2) is an environmentally friendly optical semiconductor material. It has wide application value in many fields due to its excellent structural, optical, and chemical properties. The photocatalytic process of nano-TiO2 converts light energy into electrical or chemical energy under mild conditions. In recent years, the study and application of nano-TiO2 in the agricultural sector has gradually attracted attention. The nano-TiO2 applications of degrading pesticides, plant germination and growth, crop disease control, water purification, pesticide residue detection, etc. are good prospects. This review describes all of these applications and the research status and development, including the underlying principles, features, comprehensive applications, functional modification, and potential future directions, for TiO2 in agriculture.

Nonlinear Optical Interactions in Semiconductors.

DTIC Science & Technology

1985-12-10

Physique du Solide et Energie Solaire We had on-going interaction with Dr. Christian Verie on the growth of high quality narrow-gap semiconductor crystals...The band gap energy of the semiconductor decreases with increasing temperature. Consequently, the absorption of light in the energy region of the...gas and, more importantly, will modulate the electron energy at the difference frequency, wI - 02" Under ordinary circumstances such an energy (or

Vapor Growth of Binary and Ternary Chalcogenides in Preparation for Microgravity Experiments

NASA Technical Reports Server (NTRS)

Su, C.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

In the bulk crystal growth of some technologically important semiconducting chalcopyrites, such as ZnTe, CdS, ZnSe and ZnS, vapor growth techniques have significant advantages over melt growth techniques due to the high melting points of these materials. The realization of routine production of high-quality single crystals of these semiconductors requires a fundamental, systematic and in-depth study on the PVT growth process and crystal growth by vapor transport in low gravity offers a set of unique conditions for this study. Previously, two reasons have been put forward to account for this. The first is weight-related reductions in crystal strain and defects. These are thought to be caused by the weight of the crystals during processing at elevated temperatures and retained on cooling, particularly for materials with a low yield strength. The second, and more general, reason is related to the reduction in density-gradient driven convection. The PVT crystal growth process consists of essentially three processes: sublimation of the source material, transport of the vapor species and condensation of the vapor species to form the crystal. The latter two processes can be affected by the convection caused by gravitational accelerations on Earth. Reductions in such convection in low gravity is expected to yield a nearly diffusion-limited growth condition which results in more uniform growth rates (on the microscopic scale) and hence greater crystalline perfection and compositional homogeneity. The reduction of convective contamination by performing flight experiments in a reduced gravity environment will help to understand the relation between fluid phase processes (growth parameters) and defect and impurity incorporation in grown crystals.

Crystal Growth of ZnSe by Physical Vapor Transport: A Modeling Study

NASA Technical Reports Server (NTRS)

Ramachandran, Narayanan; Su, Ching-Hua

1998-01-01

Crystal growth from the vapor phase has various advantages over melt growth. The main advantage is from a lower processing temperature which makes the process more amenable in instances where the melting temperature of the crystal is high. Other benefits stem from the inherent purification mechanism in the process due to differences in the vapor pressures of the native elements and impurities, and the enhanced interfacial morphological stability during the growth process. Further, the implementation of Physical Vapor Transport (PVT) growth in closed ampoules affords experimental simplicity with minimal needs for complex process control which makes it an ideal candidate for space investigations in systems where gravity tends to have undesirable effects on the growth process. Bulk growth of wide band gap II-VI semiconductors by physical vapor transport has been developed and refined over the past several years at NASA MSFC. Results from a modeling study of PVT crystal growth of ZnSe arc reported in this paper. The PVI process is numerically investigated using both two-dimensional and fully three-dimensional formulation of the governing equations and associated boundary conditions. Both the incompressible Boussinesq approximation and the compressible model are tested to determine the influence of gravity on the process and to discern the differences between the two approaches. The influence of a residual gas is included in the models. The preliminary results show that both the incompressible and compressible approximations provide comparable results and the presence of a residual gas tends to measurably reduce the mass flux in the system. Detailed flow, thermal and concentration profiles will be provided in the final manuscript along with computed heat and mass transfer rates. Comparisons with the 1-D model will also be provided.

Semiconductor structure and recess formation etch technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Bin; Sun, Min; Palacios, Tomas Apostol

2017-02-14

A semiconductor structure has a first layer that includes a first semiconductor material and a second layer that includes a second semiconductor material. The first semiconductor material is selectively etchable over the second semiconductor material using a first etching process. The first layer is disposed over the second layer. A recess is disposed at least in the first layer. Also described is a method of forming a semiconductor structure that includes a recess. The method includes etching a region in a first layer using a first etching process. The first layer includes a first semiconductor material. The first etching processmore » stops at a second layer beneath the first layer. The second layer includes a second semiconductor material.« less

Understanding and control of bipolar self-doping in copper nitride

NASA Astrophysics Data System (ADS)

Fioretti, Angela N.; Schwartz, Craig P.; Vinson, John; Nordlund, Dennis; Prendergast, David; Tamboli, Adele C.; Caskey, Christopher M.; Tuomisto, Filip; Linez, Florence; Christensen, Steven T.; Toberer, Eric S.; Lany, Stephan; Zakutayev, Andriy

2016-05-01

Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu3N) is a metastable semiconductor with a solar-relevant bandgap that has been reported to exhibit bipolar doping behavior. However, deeper understanding and better control of the mechanism behind this behavior in Cu3N is currently lacking in the literature. In this work, we use combinatorial growth with a temperature gradient to demonstrate both conduction types of phase-pure, sputter-deposited Cu3N thin films. Room temperature Hall effect and Seebeck effect measurements show n-type Cu3N with 1017 electrons/cm3 for low growth temperature (≈35 °C) and p-type with 1015 holes/cm3-1016 holes/cm3 for elevated growth temperatures (50 °C-120 °C). Mobility for both types of Cu3N was ≈0.1 cm2/Vs-1 cm2/Vs. Additionally, temperature-dependent Hall effect measurements indicate that ionized defects are an important scattering mechanism in p-type films. By combining X-ray absorption spectroscopy and first-principles defect theory, we determined that VCu defects form preferentially in p-type Cu3N, while Cui defects form preferentially in n-type Cu3N, suggesting that Cu3N is a compensated semiconductor with conductivity type resulting from a balance between donor and acceptor defects. Based on these theoretical and experimental results, we propose a kinetic defect formation mechanism for bipolar doping in Cu3N that is also supported by positron annihilation experiments. Overall, the results of this work highlight the importance of kinetic processes in the defect physics of metastable materials and provide a framework that can be applied when considering the properties of such materials in general.

Preparation of III-V semiconductor nanocrystals

DOEpatents

Alivisatos, A. Paul; Olshavsky, Michael A.

1996-01-01

Nanometer-scale crystals of III-V semiconductors are disclosed, They are prepared by reacting a group III metal source with a group V anion source in a liquid phase at elevated temperature in the presence of a crystallite growth terminator such as pyridine or quinoline.

Novel in situ resistance measurement for the investigation of CIGS growth in a selenization process

NASA Astrophysics Data System (ADS)

Liu, Wei; Tian, Jian-Guo; Li, Zu-Bin; He, Qing; Li, Feng-Yan; Li, Chang-Jian; Sun, Yun

2009-03-01

During the selenization process of CIGS thin films, the relation between the element loss rate and the precursor depositions are analyzed. The growth of the CIGS thin films during the selenization process is investigated by the novel in situ resistance measurement, by which the formation of compound semiconductors can be observed directly and simultaneously. Their structures, phase evolutions and element losses are analyzed by XRD and XRF. Based on the experimental results, it can be concluded that the phase transforms have nothing to do with the deposition sequences of precursors, while the element loss rates are related to the deposition sequences in this process. In addition, element loss mechanisms of CIGS thin films prepared by the selenization process are analyzed by the phase evolutions and chemical combined path in the In, Ga-Se reaction processes. Moreover it is verified that the element losses are depressed by increasing the ramping-up rate finally. The results provide effective methods to fabricate high-quality CIGS thin films with low element losses.

Growth rates and interface shapes in germanium and lead tin telluride observed in-situ, real-time in vertical Bridgman furnaces

NASA Technical Reports Server (NTRS)

Barber, P. G.; Berry, R. F.; Debnam, W. J.; Fripp, A. L.; Woodell, G.; Simchick, R. T.

1995-01-01

Using the advanced technology developed to visualize the melt-solid interface in low Prandtl number materials, crystal growth rates and interface shapes have been measured in germanium and lead tin telluride semiconductors grown in vertical Bridgman furnaces. The experimental importance of using in-situ, real time observations to determine interface shapes, to measure crystal growth rates, and to improve furnace and ampoule designs is demonstrated. The interface shapes observed in-situ, in real-time were verified by quenching and mechanically induced interface demarcation, and they were also confirmed using machined models to ascertain the absence of geometric distortions. Interface shapes depended upon the interface position in the furnace insulation zone, varied with the nature of the crystal being grown, and were dependent on the extent of transition zones at the ends of the ampoule. Actual growth rates varied significantly from the constant translation rate in response to the thermophysical properties of the crystal and its melt and the thermal conditions existing in the furnace at the interface. In the elemental semiconductor germanium the observed rates of crystal growth exceeded the imposed translation rate, but in the compound semiconductor lead tin telluride the observed rates of growth were less than the translation rate. Finally, the extent of ampoule thermal loading influenced the interface positions, the shapes, and the growth rates.

Magnetic Susceptibility Effects and Lorentz Damping in Diamagnetic Fluids

NASA Technical Reports Server (NTRS)

Ramachandran, Narayanan; Leslie, Fred W.

2000-01-01

A great number of crystals (semi-conductor and protein) grown in space are plagued by convective motions which contribute to structural flaws. The character of these instabilities is not well understood but is associated with density variations in the presence of residual gravity and g-jitter. Both static and dynamic (rotating or travelling wave) magnetic fields can be used to reduce the effects of convection in materials processing. In semi-conductor melts, due to their relatively high electrical conductivity, the induced Lorentz force can be effectively used to curtail convective effects. In melts/solutions with reduced electrical conductivity, such as aqueous solutions used in solution crystal growth, protein crystal growth and/or model fluid experiments for simulating melt growth, however, the variation of the magnetic susceptibility with temperature and/or concentration can be utilized to better damp fluid convection than the Lorentz force method. This paper presents a comprehensive, comparative numerical study of the relative damping effects using static magnetic fields and gradients in a simple geometry subjected to a thermal gradient. The governing equations are formulated in general terms and then simplified for the numerical calculations. Operational regimes, based on the best damping technique for different melts/solutions are identified based on fluid properties. Comparisons are provided between the numerical results and available results from experiments in surveyed literature.

Density functional theory in materials science.

PubMed

Neugebauer, Jörg; Hickel, Tilmann

2013-09-01

Materials science is a highly interdisciplinary field. It is devoted to the understanding of the relationship between (a) fundamental physical and chemical properties governing processes at the atomistic scale with (b) typically macroscopic properties required of materials in engineering applications. For many materials, this relationship is not only determined by chemical composition, but strongly governed by microstructure. The latter is a consequence of carefully selected process conditions (e.g., mechanical forming and annealing in metallurgy or epitaxial growth in semiconductor technology). A key task of computational materials science is to unravel the often hidden composition-structure-property relationships using computational techniques. The present paper does not aim to give a complete review of all aspects of materials science. Rather, we will present the key concepts underlying the computation of selected material properties and discuss the major classes of materials to which they are applied. Specifically, our focus will be on methods used to describe single or polycrystalline bulk materials of semiconductor, metal or ceramic form.

Direct Growth of Graphene Film on Germanium Substrate

PubMed Central

Wang, Gang; Zhang, Miao; Zhu, Yun; Ding, Guqiao; Jiang, Da; Guo, Qinglei; Liu, Su; Xie, Xiaoming; Chu, Paul K.; Di, Zengfeng; Wang, Xi

2013-01-01

Graphene has been predicted to play a role in post-silicon electronics due to the extraordinary carrier mobility. Chemical vapor deposition of graphene on transition metals has been considered as a major step towards commercial realization of graphene. However, fabrication based on transition metals involves an inevitable transfer step which can be as complicated as the deposition of graphene itself. By ambient-pressure chemical vapor deposition, we demonstrate large-scale and uniform depositon of high-quality graphene directly on a Ge substrate which is wafer scale and has been considered to replace conventional Si for the next generation of high-performance metal-oxide-semiconductor field-effect transistors (MOSFETs). The immiscible Ge-C system under equilibrium conditions dictates graphene depositon on Ge via a self-limiting and surface-mediated process rather than a precipitation process as observed from other metals with high carbon solubility. Our technique is compatible with modern microelectronics technology thus allowing integration with high-volume production of complementary metal-oxide-semiconductors (CMOS). PMID:23955352

Buried Porous Silicon-Germanium Layers in Monocrystalline Silicon Lattices

NASA Technical Reports Server (NTRS)

Fathauer, Robert W. (Inventor); George, Thomas (Inventor); Jones, Eric W. (Inventor)

1998-01-01

Monocrystalline semiconductor lattices with a buried porous semiconductor layer having different chemical composition is discussed and monocrystalline semiconductor superlattices with a buried porous semiconductor layers having different chemical composition than that of its monocrystalline semiconductor superlattice are discussed. Lattices of alternating layers of monocrystalline silicon and porous silicon-germanium have been produced. These single crystal lattices have been fabricated by epitaxial growth of Si and Si-Ge layers followed by patterning into mesa structures. The mesa structures are strain etched resulting in porosification of the Si-Ge layers with a minor amount of porosification of the monocrystalline Si layers. Thicker Si-Ge layers produced in a similar manner emitted visible light at room temperature.

Organo luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes

DOEpatents

Weiss, Shimon [Pinole, CA; Bruchez, Jr., Marcel; Alivisatos, Paul [Oakland, CA

2008-01-01

A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) an affinity molecule linked to the semiconductor nanocrystal. The semiconductor nanocrystal is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Exposure of the semiconductor nanocrystal to excitation energy will excite the semiconductor nanocrystal causing the emission of electromagnetic radiation. Further described are processes for respectively: making the luminescent semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.

Guided growth of large-scale, horizontally aligned arrays of single-walled carbon nanotubes and their use in thin-film transistors.

PubMed

Kocabas, Coskun; Hur, Seung-Hyun; Gaur, Anshu; Meitl, Matthew A; Shim, Moonsub; Rogers, John A

2005-11-01

A convenient process for generating large-scale, horizontally aligned arrays of pristine, single-walled carbon nanotubes (SWNTs) is described. The approach uses guided growth, by chemical vapor deposition (CVD), of SWNTs on miscut single-crystal quartz substrates. Studies of the growth reveal important relationships between the density and alignment of the tubes, the CVD conditions, and the morphology of the quartz. Electrodes and dielectrics patterned on top of these arrays yield thin-film transistors that use the SWNTs as effective thin-film semiconductors. The ability to build high-performance devices of this type suggests significant promise for large-scale aligned arrays of SWNTs in electronics, sensors, and other applications.

In situ synchrotron X-ray diffraction study on epitaxial-growth dynamics of III–V semiconductors

NASA Astrophysics Data System (ADS)

Takahasi, Masamitu

2018-05-01

The application of in situ synchrotron X-ray diffraction (XRD) to the molecular-beam epitaxial (MBE) growth of III–V semiconductors is overviewed along with backgrounds of the diffraction theory and instrumentation. X-rays are sensitive not only to the surface of growing films but also to buried interfacial structures because of their large penetration depth. Moreover, a spatial coherence length up to µm order makes X-rays widely applicable to the characterization of low-dimensional structures, such as quantum dots and wires. In situ XRD studies during growth were performed using an X-ray diffractometer, which was combined with an MBE chamber. X-ray reciprocal space mapping at a speed matching a typical growth rate was achieved using intense X-rays available from a synchrotron light source and an area detector. The importance of measuring the three-dimensional distribution of XRD intensity in a reciprocal space map is demonstrated for the MBE growth of two-, one-, and zero-dimensional structures. A large amount of information about the growth process of two-dimensional InGaAs/GaAs(001) epitaxial films has been provided by three-dimensional X-ray reciprocal mappings, including the anisotropic strain relaxation, the compositional inhomogeneity, and the evolution of surface and interfacial roughness. For one-dimensional GaAs nanowires grown in a Au-catalyzed vapor-liquid–solid mode, the relationship between the diameter of the nanowires and the formation of polytypes has been suggested on the basis of in situ XRD measurements. In situ three-dimensional X-ray reciprocal space mapping is also shown to be useful for determining the lateral and vertical sizes of self-assembled InAs/GaAs(001) quantum dots as well as their internal strain distributions during growth.

Floating growth of large-scale freestanding TiO2 nanorod films at the gas-liquid interface for additive-free Li-ion battery applications.

PubMed

Xia, Hua-Rong; Li, Jia; Peng, Chen; Sun, Wen-Tao; Li, Long-Wei; Peng, Lian-Mao

2014-10-22

The floating growth process of large-scale freestanding TiO2 nanorod films at the gas-liquid interface was investigated. On the basis of the experiments, a self-templated growth scenario was developed to account for the self-assembly process. In the scenario, titanium complexes function not only as the Ti source for the growth of TiO2 but also as a soft template provider for the floating growth. According to the scenario, several new recipes of preparing freestanding TiO2 nanorod films at the gas-liquid interface were developed. The freestanding film was applied to a lithium ion battery as a binder-free and conducting agent-free anode, and good cyclability was obtained. This work may pave a new way to floating and freestanding TiO2 and other semiconductor materials, which has great potential not only in basic science but also in the applications such as materials engineering, Li-ion battery, photocatalyst, dye-sensitized solar cell, and flexible electronics.

Modeling Growth of Nanostructures in Plasmas

NASA Technical Reports Server (NTRS)

Hwang, Helen H.; Bose, Deepak; Govindan, T. R.; Meyyappan, M.

2004-01-01

As semiconductor circuits shrink to CDs below 0.1 nm, it is becoming increasingly critical to replace and/or enhance existing technology with nanoscale structures, such as nanowires for interconnects. Nanowires grown in plasmas are strongly dependent on processing conditions, such as gas composition and substrate temperature. Growth occurs at specific sites, or step-edges, with the bulk growth rate of the nanowires determined from the equation of motion of the nucleating crystalline steps. Traditional front-tracking algorithms, such as string-based or level set methods, suffer either from numerical complications in higher spatial dimensions, or from difficulties in incorporating surface-intense physical and chemical phenomena. Phase field models have the robustness of the level set method, combined with the ability to implement surface-specific chemistry that is required to model crystal growth, although they do not necessarily directly solve for the advancing front location. We have adopted a phase field approach and will present results of the adatom density and step-growth location in time as a function of processing conditions, such as temperature and plasma gas composition.

Surface and Thin Film Analysis during Metal Organic Vapour Phase Epitaxial Growth

NASA Astrophysics Data System (ADS)

Richter, Wolfgang

2007-06-01

In-situ analysis of epitaxial growth is the essential ingredient in order to understand the growth process, to optimize growth and last but not least to monitor or even control the epitaxial growth on a microscopic scale. In MBE (molecular beam epitaxy) in-situ analysis tools existed right from the beginning because this technique developed from Surface Science technology with all its electron based analysis tools (LEED, RHEED, PES etc). Vapour Phase Epitaxy, in contrast, remained for a long time in an empirical stage ("alchemy") because only post growth characterisations like photoluminescence, Hall effect and electrical conductivity were available. Within the last two decades, however, optical techniques were developed which provide similar capabilities as in MBE for Vapour Phase growth. I will discuss in this paper the potential of Reflectance Anisotropy Spectroscopy (RAS) and Spectroscopic Ellipsometry (SE) for the growth of thin epitaxial semiconductor layers with zincblende (GaAs etc) and wurtzite structure (GaN etc). Other techniques and materials will be also mentioned.

Kinetics of Semiconductor Surface Chemistry: Silicon Atomic Layer Processing

DTIC Science & Technology

1993-05-01

H20 --> Si-OH + HCI; and (B) Si-OH + SiCl4 -- > Si-O-SiCl 3 + HC1. We examined reaction (A) for SiO 2 growth on Si(111)7x7 and porous silicon and... SiCl4 > Si-O-SiCl3 + HCI Repeat... • Reaction (A) and (B) are self-limiting * Expect excellent conformality Si-Cl + H20 ->Si-OH + HC1 SiCl2 LITD

Electromagnetic Field Effects in Semiconductor Crystal Growth

NASA Technical Reports Server (NTRS)

Dulikravich, George S.

1996-01-01

This proposed two-year research project was to involve development of an analytical model, a numerical algorithm for its integration, and a software for the analysis of a solidification process under the influence of electric and magnetic fields in microgravity. Due to the complexity of the analytical model that was developed and its boundary conditions, only a preliminary version of the numerical algorithm was developed while the development of the software package was not completed.

Band-Gap Engineering at a Semiconductor-Crystalline Oxide Interface

DOE PAGES

Jahangir-Moghadam, Mohammadreza; Ahmadi-Majlan, Kamyar; Shen, Xuan; ...

2015-02-09

The epitaxial growth of crystalline oxides on semiconductors provides a pathway to introduce new functionalities to semiconductor devices. Key to integrating the functionalities of oxides onto semiconductors is controlling the band alignment at interfaces between the two materials. Here we apply principles of band gap engineering traditionally used at heterojunctions between conventional semiconductors to control the band offset between a single crystalline oxide and a semiconductor. Reactive molecular beam epitaxy is used to realize atomically abrupt and structurally coherent interfaces between SrZr xTi 1-xO₃ and Ge, in which the band gap of the former is enhanced with Zr content x.more » We present structural and electrical characterization of SrZr xTi 1-xO₃-Ge heterojunctions and demonstrate a type-I band offset can be achieved. These results demonstrate that band gap engineering can be exploited to realize functional semiconductor crystalline oxide heterojunctions.« less

Defect Characterization in Semiconductors with Positron Annihilation Spectroscopy

NASA Astrophysics Data System (ADS)

Tuomisto, Filip

Positron annihilation spectroscopy is an experimental technique that allows the selective detection of vacancy defects in semiconductors, providing a means to both identify and quantify them. This chapter gives an introduction to the principles of the positron annihilation techniques and then discusses the physics of some interesting observations on vacancy defects related to growth and doping of semiconductors. Illustrative examples are selected from studies performed in silicon, III-nitrides, and ZnO.

Preparation of III-V semiconductor nanocrystals

DOEpatents

Alivisatos, A.P.; Olshavsky, M.A.

1996-04-09

Nanometer-scale crystals of III-V semiconductors are disclosed. They are prepared by reacting a group III metal source with a group V anion source in a liquid phase at elevated temperature in the presence of a crystallite growth terminator such as pyridine or quinoline. 4 figs.

Epitaxial growth of CoO films on semiconductor and metal substrates by constructing a complex heterostructure

NASA Astrophysics Data System (ADS)

Entani, S.; Kiguchi, M.; Saiki, K.; Koma, A.

2003-01-01

Epitaxial growth of CoO films was studied using reflection high-energy electron diffraction (RHEED), electron energy loss spectroscopy (EELS), ultraviolet photoelectron spectroscopy (UPS) and Auger electron spectroscopy (AES). The RHEED results indicated that an epitaxial CoO film grew on semiconductor and metal substrates (CoO (0 0 1)∥GaAs (0 0 1), Cu (0 0 1), Ag (0 0 1) and [1 0 0]CoO∥[1 0 0] substrates) by constructing a complex heterostructure with two alkali halide buffer layers. The AES, EELS and UPS results showed that the grown CoO film had almost the same electronic structure as bulk CoO. We could show that use of alkali halide buffer layers was a good way to grow metal oxide films on semiconductor and metal substrates in an O 2 atmosphere. The alkali halide layers not only works as glue to connect very dissimilar materials but also prevents oxidation of metal and semiconductor substrates.

Phase diagram of nanoscale alloy particles used for vapor-liquid-solid growth of semiconductor nanowires.

PubMed

Sutter, Eli; Sutter, Peter

2008-02-01

We use transmission electron microscopy observations to establish the parts of the phase diagram of nanometer sized Au-Ge alloy drops at the tips of Ge nanowires (NWs) that determine their temperature-dependent equilibrium composition and, hence, their exchange of semiconductor material with the NWs. We find that the phase diagram of the nanoscale drop deviates significantly from that of the bulk alloy, which explains discrepancies between actual growth results and predictions on the basis of the bulk-phase equilibria. Our findings provide the basis for tailoring vapor-liquid-solid growth to achieve complex one-dimensional materials geometries.

Vacuum-and-solvent-free fabrication of organic semiconductor layers for field-effect transistors

PubMed Central

Matsushima, Toshinori; Sandanayaka, Atula S. D.; Esaki, Yu; Adachi, Chihaya

2015-01-01

We demonstrate that cold and hot isostatic pressing (CIP and HIP) is a novel, alternative method for organic semiconductor layer fabrication, where organic powder is compressed into a layer shape directly on a substrate with 200 MPa pressure. Spatial gaps between powder particles and the other particles, substrates, or electrodes are crushed after CIP and HIP, making it possible to operate organic field-effect transistors (OFETs) containing the compressed powder as the semiconductor. The CIP-compressed powder of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) had a hole mobility of (1.6 ± 0.4) × 10–2 cm2/Vs. HIP of C8-BTBT powder increased the hole mobility to an amorphous silicon-like value (0.22 ± 0.07 cm2/Vs) because of the growth of the C8-BTBT crystallites and the improved continuity between the powder particles. The vacuum and solution processes are not involved in our CIP and HIP techniques, offering a possibility of manufacturing OFETs at low cost. PMID:26416434

Vacuum-and-solvent-free fabrication of organic semiconductor layers for field-effect transistors.

PubMed

Matsushima, Toshinori; Sandanayaka, Atula S D; Esaki, Yu; Adachi, Chihaya

2015-09-29

We demonstrate that cold and hot isostatic pressing (CIP and HIP) is a novel, alternative method for organic semiconductor layer fabrication, where organic powder is compressed into a layer shape directly on a substrate with 200 MPa pressure. Spatial gaps between powder particles and the other particles, substrates, or electrodes are crushed after CIP and HIP, making it possible to operate organic field-effect transistors (OFETs) containing the compressed powder as the semiconductor. The CIP-compressed powder of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) had a hole mobility of (1.6 ± 0.4) × 10(-2) cm(2)/Vs. HIP of C8-BTBT powder increased the hole mobility to an amorphous silicon-like value (0.22 ± 0.07 cm(2)/Vs) because of the growth of the C8-BTBT crystallites and the improved continuity between the powder particles. The vacuum and solution processes are not involved in our CIP and HIP techniques, offering a possibility of manufacturing OFETs at low cost.

Vacuum-and-solvent-free fabrication of organic semiconductor layers for field-effect transistors

NASA Astrophysics Data System (ADS)

Matsushima, Toshinori; Sandanayaka, Atula S. D.; Esaki, Yu; Adachi, Chihaya

2015-09-01

We demonstrate that cold and hot isostatic pressing (CIP and HIP) is a novel, alternative method for organic semiconductor layer fabrication, where organic powder is compressed into a layer shape directly on a substrate with 200 MPa pressure. Spatial gaps between powder particles and the other particles, substrates, or electrodes are crushed after CIP and HIP, making it possible to operate organic field-effect transistors (OFETs) containing the compressed powder as the semiconductor. The CIP-compressed powder of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) had a hole mobility of (1.6 ± 0.4) × 10-2 cm2/Vs. HIP of C8-BTBT powder increased the hole mobility to an amorphous silicon-like value (0.22 ± 0.07 cm2/Vs) because of the growth of the C8-BTBT crystallites and the improved continuity between the powder particles. The vacuum and solution processes are not involved in our CIP and HIP techniques, offering a possibility of manufacturing OFETs at low cost.

Size Dependence of Doping by a Vacancy Formation Reaction in Copper Sulfide Nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elimelech, Orian; Liu, Jing; Plonka, Anna M.

Doping of nanocrystals (NCs) is a key, yet underexplored, approach for tuning of the electronic properties of semiconductors. An important route for doping of NCs is by vacancy formation. The size and concentration dependence of doping was studied in copper(I) sulfide (Cu2S) NCs through a redox reaction with iodine molecules (I2), which formed vacancies accompanied by a localized surface plasmon response. X-ray spectroscopy and diffraction reveal transformation from Cu2S to Cu-depleted phases, along with CuI formation. Greater reaction efficiency was observed for larger NCs. This behavior is attributed to interplay of the vacancy formation energy, which decreases for smaller sizedmore » NCs, and the growth of CuI on the NC surface, which is favored on well-defined facets of larger NCs. This doping process allows tuning of the plasmonic properties of a semiconductor across a wide range of plasmonic frequencies by varying the size of NCs and the concentration of iodine. Controlled vacancy doping of NCs may be used to tune and tailor semiconductors for use in optoelectronic applications.« less

Melt-growth dynamics in CdTe crystals

DOE PAGES

Zhou, X. W.; Ward, D. K.; Wong, B. M.; ...

2012-06-01

We use a new, quantum-mechanics-based bond-order potential (BOP) to reveal melt growth dynamics and fine scale defect formation mechanisms in CdTe crystals. Previous molecular dynamics simulations of semiconductors have shown qualitatively incorrect behavior due to the lack of an interatomic potential capable of predicting both crystalline growth and property trends of many transitional structures encountered during the melt → crystal transformation. Here, we demonstrate successful molecular dynamics simulations of melt growth in CdTe using a BOP that significantly improves over other potentials on property trends of different phases. Our simulations result in a detailed understanding of defect formation during themore » melt growth process. Equally important, we show that the new BOP enables defect formation mechanisms to be studied at a scale level comparable to empirical molecular dynamics simulation methods with a fidelity level approaching quantum-mechanical methods.« less

An ultrahigh vacuum, low-energy ion-assisted deposition system for III-V semiconductor film growth

NASA Astrophysics Data System (ADS)

Rohde, S.; Barnett, S. A.; Choi, C.-H.

1989-06-01

A novel ion-assisted deposition system is described in which the substrate and growing film can be bombarded with high current densities (greater than 1 mA/sq cm) of very low energy (10-200 eV) ions. The system design philosophy is similar to that used in III-V semiconductor molecular-beam epitaxy systems: the chamber is an all-metal ultrahigh vacuum system with liquid-nitrogen-cooled shrouds, Knudsen-cell evaporation sources, a sample insertion load-lock, and a 30-kV reflection high-energy electron diffraction system. III-V semiconductor film growth is achieved using evaporated group-V fluxes and group-III elemental fluxes sputtered from high-purity targets using ions extracted from a triode glow discharge. Using an In target and an As effusion cell, InAs deposition rates R of 2 microns/h have been obtained. Epitaxial growth of InAs was observed on both GaSb(100) and Si(100) substrates.

Thermoelectric generator and method for the fabrication thereof

DOEpatents

Benson, David K.; Tracy, C. Edwin

1987-01-01

A thermoelectric generator using semiconductor elements for responding to a temperature gradient to produce electrical energy with all of the semiconductor elements being of the same type is disclosed. A continuous process for forming substrates on which the semiconductor elements and superstrates are deposited and a process for forming the semiconductor elements on the substrates are also disclosed. The substrates with the semiconductor elements thereon are combined with superstrates to form modules for use thermoelectric generators.

Thermoelectric generator and method for the fabrication thereof

DOEpatents

Benson, D.K.; Tracy, C.E.

1984-08-01

A thermoelectric generator using semiconductor elements for responding to a temperature gradient to produce electrical energy with all of the semiconductor elements being of the same type is disclosed. A continuous process for forming substrates on which the semiconductor elements and superstrates are deposited and a process for forming the semiconductor elements on the substrates are also disclosed. The substrates with the semiconductor elements thereon are combined with superstrates to form modules for use as thermoelectric generators.

Crystal growth of device quality GaAs in space

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Lagowski, J.

1983-01-01

GaAs device technology has recently reached a new phase of rapid advancement, made possible by the improvement of the quality of GaAs bulk crystals. At the same time, the transition to the next generation of GaAs integrated circuits and optoelectronic systems for commercial and government applications hinges on new quantum steps in three interrelated areas: crystal growth, device processing and device-related properties and phenomena. Special emphasis is placed on the establishment of quantitative relationships among crystal growth parameters-material properties-electronic properties and device applications. The overall program combines studies of crystal growth on novel approaches to engineering of semiconductor material (i.e., GaAs and related compounds); investigation and correlation of materials properties and electronic characteristics on a macro- and microscale; and investigation of electronic properties and phenomena controlling device applications and device performance.

High-quality bulk hybrid perovskite single crystals within minutes by inverse temperature crystallization

NASA Astrophysics Data System (ADS)

Saidaminov, Makhsud I.; Abdelhady, Ahmed L.; Murali, Banavoth; Alarousu, Erkki; Burlakov, Victor M.; Peng, Wei; Dursun, Ibrahim; Wang, Lingfei; He, Yao; Maculan, Giacomo; Goriely, Alain; Wu, Tom; Mohammed, Omar F.; Bakr, Osman M.

2015-07-01

Single crystals of methylammonium lead trihalide perovskites (MAPbX3; MA=CH3NH3+, X=Br- or I-) have shown remarkably low trap density and charge transport properties; however, growth of such high-quality semiconductors is a time-consuming process. Here we present a rapid crystal growth process to obtain MAPbX3 single crystals, an order of magnitude faster than previous reports. The process is based on our observation of the substantial decrease of MAPbX3 solubility, in certain solvents, at elevated temperatures. The crystals can be both size- and shape-controlled by manipulating the different crystallization parameters. Despite the rapidity of the method, the grown crystals exhibit transport properties and trap densities comparable to the highest quality MAPbX3 reported to date. The phenomenon of inverse or retrograde solubility and its correlated inverse temperature crystallization strategy present a major step forward for advancing the field on perovskite crystallization.

Examination of the nature of lattice matched III V semiconductor interfaces using computer simulated molecular beam epitaxial growth I. AC/BC interfaces

NASA Astrophysics Data System (ADS)

Thomsen, M.; Ghaisas, S. V.; Madhukar, A.

1987-07-01

A previously developed computer simulation of molecular beam epitaxial growth of III-V semiconductors based on the configuration dependent reactive incorporation (CDRI) model is extended to allow for two different cation species. Attention is focussed on examining the nature of interfaces formed in lattice matched quantum well structures of the form AC/BC/AC(100). We consider cation species with substantially different effective diffusion lengths, as is the case with Al and Ga during the growth of their respective As compounds. The degree of intermixing occuring at the interface is seen to be dependent upon, among other growth parameters, the pressure of the group V species during growth. Examination of an intraplanar order parameter at the interfaces reveals the existence of short range clustering of the cation species.

A stable solution-processed polymer semiconductor with record high-mobility for printed transistors

PubMed Central

Li, Jun; Zhao, Yan; Tan, Huei Shuan; Guo, Yunlong; Di, Chong-An; Yu, Gui; Liu, Yunqi; Lin, Ming; Lim, Suo Hon; Zhou, Yuhua; Su, Haibin; Ong, Beng S.

2012-01-01

Microelectronic circuits/arrays produced via high-speed printing instead of traditional photolithographic processes offer an appealing approach to creating the long-sought after, low-cost, large-area flexible electronics. Foremost among critical enablers to propel this paradigm shift in manufacturing is a stable, solution-processable, high-performance semiconductor for printing functionally capable thin-film transistors — fundamental building blocks of microelectronics. We report herein the processing and optimisation of solution-processable polymer semiconductors for thin-film transistors, demonstrating very high field-effect mobility, high on/off ratio, and excellent shelf-life and operating stabilities under ambient conditions. Exceptionally high-gain inverters and functional ring oscillator devices on flexible substrates have been demonstrated. This optimised polymer semiconductor represents a significant progress in semiconductor development, dispelling prevalent skepticism surrounding practical usability of organic semiconductors for high-performance microelectronic devices, opening up application opportunities hitherto functionally or economically inaccessible with silicon technologies, and providing an excellent structural framework for fundamental studies of charge transport in organic systems. PMID:23082244

Semiconductor millimeter wavelength electronics

NASA Astrophysics Data System (ADS)

Rosenbaum, F. J.

1985-12-01

This final report summarizes the results of research carried out on topics in millimeter wavelength semiconductor electronics under an ONR Selected Research Opportunity program. Study areas included III-V compound semiconductor growth and characterization, microwave and millimeter wave device modeling, fabrication and testing, and the development of new device concepts. A new millimeter wave mixer and detector, the Gap diode was invented. Topics reported on include ballistic transport, Zener oscillations, impurities in GaAs, electron velocity-electric field calculation and measurements, etc., calculations.

Quantum-Dot Laser for Wavelengths of 1.8 to 2.3 micron

NASA Technical Reports Server (NTRS)

Qiu, Yueming

2006-01-01

The figure depicts a proposed semiconductor laser, based on In(As)Sb quantum dots on a (001) InP substrate, that would operate in the wavelength range between 1.8 and 2.3 m. InSb and InAsSb are the smallest-bandgap conventional III-V semiconductor materials, and the present proposal is an attempt to exploit the small bandgaps by using InSb and InAsSb nanostructures as midinfrared emitters. The most closely related prior III-V semiconductor lasers are based, variously, on strained InGaAs quantum wells and InAs quantum dots on InP substrates. The emission wavelengths of these prior devices are limited to about 2.1 m because of critical quantum-well thickness limitations for these lattice mismatched material systems. The major obstacle to realizing the proposed laser is the difficulty of fabricating InSb quantum dots in sufficient density on an InP substrate. This difficulty arises partly because of the weakness of the bond between In and Sb and partly because of the high temperature needed to crack metalorganic precursor compounds during the vapor-phase epitaxy used to grow quantum dots: The mobility of the weakly bound In at the high growth temperature is so high that In adatoms migrate easily on the growth surface, resulting in the formation of large InSb islands at a density, usually less than 5 x 10(exp 9) cm(exp -2), that is too low for laser operation. The mobility of the In adatoms could be reduced by introducing As atoms to the growth surface because the In-As bond is about 30 percent stronger than is the In-Sb bond. The fabrication of the proposed laser would include a recently demonstrated process that involves the use of alternative supplies of precursors to separate group-III and group-V species to establish local non-equilibrium process conditions, so that In(As)Sb quantum dots assemble themselves on a (001) InP substrate at a density as high as 4 x 10(exp 10) cm(exp -2). Room-temperature photoluminescence spectra of quantum dots formed by this process indicate that they emit at wavelengths from 1.7 to 2.3 microns.

Growth of coincident site lattice matched semiconductor layers and devices on crystalline substrates

DOEpatents

Norman, Andrew G; Ptak, Aaron J

2013-08-13

Methods of fabricating a semiconductor layer or device and said devices are disclosed. The methods include but are not limited to providing a substrate having a crystalline surface with a known lattice parameter (a). The method further includes growing a crystalline semiconductor layer on the crystalline substrate surface by coincident site lattice matched epitaxy, without any buffer layer between the crystalline semiconductor layer and the crystalline surface of the substrate. The crystalline semiconductor layer will be prepared to have a lattice parameter (a') that is related to the substrate lattice parameter (a). The lattice parameter (a') maybe related to the lattice parameter (a) by a scaling factor derived from a geometric relationship between the respective crystal lattices.

Generic process for preparing a crystalline oxide upon a group IV semiconductor substrate

DOEpatents

McKee, Rodney A.; Walker, Frederick J.; Chisholm, Matthew F.

2000-01-01

A process for growing a crystalline oxide epitaxially upon the surface of a Group IV semiconductor, as well as a structure constructed by the process, is described. The semiconductor can be germanium or silicon, and the crystalline oxide can generally be represented by the formula (AO).sub.n (A'BO.sub.3).sub.m in which "n" and "m" are non-negative integer repeats of planes of the alkaline earth oxides or the alkaline earth-containing perovskite oxides. With atomic level control of interfacial thermodynamics in a multicomponent semiconductor/oxide system, a highly perfect interface between a semiconductor and a crystalline oxide can be obtained.

Critical thickness of transition from 2D to 3D growth and peculiarities of quantum dots formation in GexSi1-x/Sn/Si and Ge1-ySny/Si systems

NASA Astrophysics Data System (ADS)

Lozovoy, Kirill A.; Kokhanenko, Andrey P.; Voitsekhovskii, Alexander V.

2018-03-01

Nowadays using of tin as one of the deposited materials in GeSi/Sn/Si, GeSn/Si and GeSiSn/Si material systems is one of the most topical problems. These materials are very promising for various applications in nanoelectronics and optoelectronics due to possibility of band gap management and synthesis of direct band semiconductors within these systems. However, there is a lack of theoretical investigations devoted to the peculiarities of germanium on silicon growth in the presence of tin. In this paper a new theoretical approach for modeling growth processes of binary and ternary semiconductor compounds during the molecular beam epitaxy in these systems is presented. The established kinetic model based on the general nucleation theory takes into account the change in physical and mechanical parameters, diffusion coefficient and surface energies in the presence of tin. With the help of the developed model the experimentally observed significant decrease in the 2D-3D transition temperatures for GeSiSn/Si system compared to GeSi/Si system is theoretically explained for the first time in the literature. Besides that, the derived expressions allow one to explain the experimentally observed temperature dependencies of the critical thickness, as well as to predict the average size and surface density of quantum dots for different contents and temperatures in growth experiment, that confirms applicability of the model proposed. Moreover, the established model can be easily applied to other material systems in which the Stranski-Krastanow growth mode occurs.

Diamond deposition using a planar radio frequency inductively coupled plasma

NASA Astrophysics Data System (ADS)

Bozeman, S. P.; Tucker, D. A.; Stoner, B. R.; Glass, J. T.; Hooke, W. M.

1995-06-01

A planar radio frequency inductively coupled plasma has been used to deposit diamond onto scratched silicon. This plasma source has been developed recently for use in large area semiconductor processing and holds promise as a method for scale up of diamond growth reactors. Deposition occurs in an annulus which coincides with the area of most intense optical emission from the plasma. Well-faceted diamond particles are produced when the substrate is immersed in the plasma.

Morphology, Microstructure and Transport Properties of ZnO Decorated SiO2 Nanoparticles (Preprint)

DTIC Science & Technology

2010-04-15

ZnO decorated SiO2 nanoparticles . While the growth conditions we employ for synthesis of ZnO nanocrys- tals are similar to... oxide nanocrystal synthesis on semiconductor oxide nanoparticles is an area yet to be fully explored. One advantage of this approach is that it enables... nanoparticles were resuspended. This washing process was repeated three times. In the hydrolytic ZnO synthesis method, a 1 ml suspension of SiO2 nanoshells

V x In (2–x) S 3 Intermediate Band Absorbers Deposited by Atomic Layer Deposition

DOE PAGES

McCarthy, Robert F.; Weimer, Matthew S.; Haasch, Richard T.; ...

2016-03-21

Substitutional alloys of several thin film semiconductors have been proposed as intermediate band (IB) materials for use in next-generation photovoltaics, which aim to utilize a larger fraction of the solar spectrum without sacrificing significant photovoltage. Here, we demonstrate a novel approach to IB material growth, namely atomic layer deposition (ALD), to enable unique control over substitutional-dopant location and density. Two new ALD processes for vanadium sulfide incorporation are introduced, one of which incorporates a vanadium (III) amidinate previously untested for ALD. We synthesize the first thin film V xIn (2-x)S 3 intermediate band semiconductors, using this process, and further demonstratemore » that the V:In ratio, and therefore intraband gap density of states, can be finely tuned according to the ALD dosing schedule. Deposition on a crystalline In 2S 3 underlayer promotes the growth of a tetragonal β-In 2S 3-like phase V xIn (2-x)S 3, which exhibits a distinct sub-band gap absorption peak with onset near 1.1 eV in agreement with computational predictions. But, the V xIn (2-x)S 3 films lack the lower energy transition predicted for a partially filled IB, and photoelectrochemical devices reveal a photocurrent response only from illumination with energy sufficient to span the parent band-gap.« less

Stable surface passivation process for compound semiconductors

DOEpatents

Ashby, Carol I. H.

2001-01-01

A passivation process for a previously sulfided, selenided or tellurated III-V compound semiconductor surface. The concentration of undesired mid-gap surface states on a compound semiconductor surface is reduced by the formation of a near-monolayer of metal-(sulfur and/or selenium and/or tellurium)-semiconductor that is effective for long term passivation of the underlying semiconductor surface. Starting with the III-V compound semiconductor surface, any oxidation present thereon is substantially removed and the surface is then treated with sulfur, selenium or tellurium to form a near-monolayer of chalcogen-semiconductor of the surface in an oxygen-free atmosphere. This chalcogenated surface is then contacted with a solution of a metal that will form a low solubility chalcogenide to form a near-monolayer of metal-chalcogen-semiconductor. The resulting passivating layer provides long term protection for the underlying surface at or above the level achieved by a freshly chalcogenated compound semiconductor surface in an oxygen free atmosphere.

Superheating Suppresses Structural Disorder in Layered BiI3 Semiconductors Grown by the Bridgman Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johns, Paul M.; Sulekar, Soumitra; Yeo, Shinyoung

2016-01-01

The susceptibility of layered structures to stacking faults is a problem in some of the more attractive semiconductor materials for ambient-temperature radiation detectors. In the work presented here, Bridgman-grown BiI3 layered single crystals are investigated to understand and eliminate this structural disorder, which reduces radiation detector performance. The use of superheating gradients has been shown to improve crystal quality in non-layered semiconductor crystals; thus the technique was here explored to improve the growth of BiI3. When investigating the homogeneity of non-superheated crystals, highly geometric void defects were found to populate the bulk of the crystals. Applying a superheating gradient tomore » the melt prior to crystal growth improved structural quality and decreased defect density from the order of 4600 voids per cm3 to 300 voids per cm3. Corresponding moderate improvements to electronic properties also resulted from the superheat gradient method of crystal growth. Comparative measurements through infrared microscopy, etch-pit density, x-ray rocking curves, and sheet resistivity readings show that superheat gradients in BiI3 growth led to higher quality crystals.« less

Semiconductor crystal growth in crossed electric and magnetic fields: Center Director's Discretionary Fund

NASA Technical Reports Server (NTRS)

Mazuruk, K.; Volz, M. P.

1996-01-01

A unique growth cell was designed in which crossed electric and magnetic fields could be separately or simultaneously applied during semiconductor crystal growth. A thermocouple was inserted into an InSb melt inside the growth cell to examine the temperature response of the fluid to applied electromagnetic fields. A static magnetic field suppressed time-dependent convection when a destabilizing thermal field was applied. The simultaneous application of electric and magnetic fields resulted in forced convection in the melt. The InSb ingots grown in the cell were polycrystalline. An InGaSb crystal, 0.5 cm in diameter and 23-cm long, was grown without electromagnetic fields applied. The axial composition results indicated that complete mixing in the melt occurred for this large aspect ratio.

Materials processing threshold report. 1: Semiconductor crystals for infrared detectors

NASA Technical Reports Server (NTRS)

Sager, E. V.; Thompson, T. R.; Nagler, R. G.

1980-01-01

An extensive search was performed of the open literature pertaining to infrared detectors to determine what constitutes a good detector and in what way performance is limited by specific material properties. Interviews were conducted with a number of experts in the field to assess their perceptions of the state of the art and of the utility of zero-gravity processing. Based on this information base and on a review of NASA programs in crystal growth and infrared sensors, NASA program goals were reassessed and suggestions are presented as to possible joint and divergent efforts between NASA and DOD.

III-V semiconductor solid solution single crystal growth

NASA Technical Reports Server (NTRS)

Gertner, E. R.

1982-01-01

The feasibility and desirability of space growth of bulk IR semiconductor crystals for use as substrates for epitaxial IR detector material were researched. A III-V ternary compound (GaInSb) and a II-VI binary compound were considered. Vapor epitaxy and quaternary epitaxy techniques were found to be sufficient to permit the use of ground based binary III-V crystals for all major device applications. Float zoning of CdTe was found to be a potentially successful approach to obtaining high quality substrate material, but further experiments were required.

Manufacturing of High-Efficiency Bi-Facial Tandem Concentrator Solar Cells: February 20, 2009--August 20, 2010

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wojtczuk , S.

2011-06-01

Spire Semiconductor made concentrator photovoltaic (CPV) cells using a new bi-facial growth process and met both main program goals: a) 42.5% efficiency 500X (AM1.5D, 25C, 100mW/cm2); and b) Ready to supply at least 3MW/year of such cells at end of program. We explored a unique simple fabrication process to make a N/P 3-junction InGaP/GaAs/InGaAs tandem cells . First, the InGaAs bottom cell is grown on the back of a GaAs wafer. The wafers are then loaded into a cassette, spin-rinsed to remove particles, dipped in dilute NH4OH and spin-dried. The wafers are then removed from the cassette loaded the reactormore » for GaAs middle and InGaP top cell growth on the opposite wafer face (bi-facial growth). By making the epitaxial growth process a bit more complex, we are able to avoid more complex processing (such as large area wafer bonding or epitaxial liftoff) used in the inverted metamorphic (IMM) approach to make similar tandem stacks. We believe the yield is improved compared to an IMM process. After bi-facial epigrowth, standard III-V cell steps (back metal, photolithography for front grid, cap etch, AR coat, dice) are used in the remainder of the process.« less

Laminar mixing in a small floating zone

NASA Technical Reports Server (NTRS)

Harriott, George M.

1987-01-01

The relationship between the flow and solute fields during steady mass transfer of a dilute component is analyzed for multi-cellular rotating flows in the floating zone process of semiconductor growth. When the recirculating flows are weak in relation to the rate of crystal growth, a closed-form solution clearly shows the link between the convection pattern in the melt and the solute distribution across the surface of the growing solid. In the limit of strong convection, finite element calculations demonstrate the tendency of the composition to become uniform over the majority of the melt. The solute segregation in the product crystal is greatest when the recirculating motion is comparable to the rate of crystal growth, and points to the danger in attempting to grow compositionally uniform materials from a nearly convectionless melt.

Low-Cost Approaches to III–V Semiconductor Growth for Photovoltaic Applications

DOE PAGES

Greenaway, Ann L.; Boucher, Jason W.; Oener, Sebastian Z.; ...

2017-08-31

III–V semiconductors form the most efficient single- and multijunction photovoltaics. Metal–organic vapor-phase epitaxy, which uses toxic and pyrophoric gas-phase precursors, is the primary commercial growth method for these materials. In order for the use of highly efficient III–V-based devices to be expanded as the demand for renewable electricity grows, a lower-cost approach to the growth of these materials is needed. This Review focuses on three deposition techniques compatible with current device architectures: hydride vapor-phase epitaxy, close-spaced vapor transport, and thin-film vapor–liquid–solid growth. Here, we consider recent advances in each technique, including the available materials space, before providing an in-depth comparisonmore » of growth technology advantages and limitations and considering the impact of modifications to the method of production on the cost of the final photovoltaics.« less

Materials Science Laboratory - Columnar-to-Equiaxed Transition in Solidification Processing and Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions

NASA Technical Reports Server (NTRS)

Gandin, Charles-Andre; Ratke, Lorenz

2008-01-01

The Materials Science Laboratory - Columnar-to-Equiaxed Transition in Solidification Processing and Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions (MSL-CETSOL and MICAST) are two investigations which supports research into metallurgical solidification, semiconductor crystal growth (Bridgman and zone melting), and measurement of thermo-physical properties of materials. This is a cooperative investigation with the European Space Agency (ESA) and National Aeronautics and Space Administration (NASA) for accommodation and operation aboard the International Space Station (ISS). Research Summary: Materials Science Laboratory - Columnar-to-Equiaxed Transition in Solidification Processing (CETSOL) and Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions (MICAST) are two complementary investigations which will examine different growth patterns and evolution of microstructures during crystallization of metallic alloys in microgravity. The aim of these experiments is to deepen the quantitative understanding of the physical principles that govern solidification processes in cast alloys by directional solidification.

Plasma Processing of Metallic and Semiconductor Thin Films in the Fisk Plasma Source

NASA Technical Reports Server (NTRS)

Lampkin, Gregory; Thomas, Edward, Jr.; Watson, Michael; Wallace, Kent; Chen, Henry; Burger, Arnold

1998-01-01

The use of plasmas to process materials has become widespread throughout the semiconductor industry. Plasmas are used to modify the morphology and chemistry of surfaces. We report on initial plasma processing experiments using the Fisk Plasma Source. Metallic and semiconductor thin films deposited on a silicon substrate have been exposed to argon plasmas. Results of microscopy and chemical analyses of processed materials are presented.

Evolution of the Shape of Detached GeSi Crystals in Microgravity

NASA Technical Reports Server (NTRS)

Volz, M. P.; Mazuruk, K.

2013-01-01

A series of GeSi crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. An objective of these experiments is to understand the mechanisms of detached Bridgman growth, a process in which a gap exists between the growing semiconductor crystal and the crucible wall. Crystals grown without wall contact have superior quality to otherwise similar crystals grown in direct contact with a container, especially with respect to impurity incorporation, formation of dislocations, and residual stress in crystals. Numerical calculations are used to determine the conditions in which a gap can exist. According to crystal shape stability theory, only some of these gap widths will be dynamically stable. Beginning with a crystal diameter that differs from stable conditions, the transient crystal growth process is analyzed. In microgravity, dynamic stability depends only on capillary effects and is decoupled from heat transfer. Depending on the initial conditions and growth parameters, the crystal shape will evolve towards the crucible wall, towards a stable gap width, or towards the center of the crucible, collapsing the meniscus.

Synthesis and characterization of group IV semiconductor nanowires by vapor-liquid-solid growth

NASA Astrophysics Data System (ADS)

Lew, Kok-Keong

There is currently intense interest in one-dimensional nanostructures, such as nanotubes and nanowires, due to their potential to test fundamental concepts of dimensionality and to serve as building blocks for nanoscale devices. Vapor-liquid-solid (VLS) growth, which is one of the most common fabrication methods, has been used to produce single crystal semiconductor nanowires such as silicon (Si), germanium (Ge), and gallium arsenide (GaAs). In the VLS growth of Group IV semiconductor nanowires, a metal, such as gold (Au) is used as a catalyst agent to nucleate whisker growth from a Si-containing (silane (SIH4)) or Ge-containing vapor (germane (GeH 4)). Au and Si/Ge form a liquid alloy that has a eutectic temperature of around 360°C, which, upon supersaturation, nucleates the growth of a Si or Ge wire. The goal of this work is to develop a more fundamental understanding of VLS growth kinetics and intentional doping of Group IV semiconductor nanowires in order to better control the properties of the nanowires. The fabrication of p-type and n-type Si nanowires will be studied via the addition of dopant gases such as diborane (B2H 6), trimethylboron (TMB), and phosphine (PH3) during growth. The use of gaseous dopant sources provides more flexibility in growth, particularly for the fabrication of p-n junctions and structures with axial dopant variations (e.g. p+-p- p+). The study is then extended to fabricate SiGe alloy nanowires by mixing SiH4 and GeH4. Bandgap engineering in Si/SiGe heterostructures can lead to novel devices with improved performance compared to those made entirely of Si. The scientific findings will lead to a better understanding of the fabrication of Si/SiGe axial and radial heterostructure nanowires for functional nanowire device structures, such as heterojunction bipolar transistors (HBTs) and high electron mobility transistors (HEMTs). Eventually, the central theme of this research is to provide a scientific knowledge base and foundation for the design of Si, Ge, and SiGe nanostructures that will be of importance in nanoscale device applications.

Microgravity sciences application visiting scientist program

NASA Technical Reports Server (NTRS)

1994-01-01

Contract NAS8-38785, Microgravity Experimental and Theoretical Research, is a project involving a large number of individual research programs related to: determination of the structure of human serum albumin and other biomedically important proteins; analysis of thermodynamic properties of various proteins and models of protein nucleation; development of experimental techniques for the growth of protein crystals in space; study of the physics of electrical double layers in the mechanics of liquid interfaces; computational analysis of vapor crystal growth processes in microgravity; analysis of the influence of magnetic fields in damping residual flows in directional solidification processes; crystal growth and characterization of II-VI semiconductor alloys; and production of thin films for nonlinear optics. It is not intended that the programs will be necessarily limited to this set at any one time. The visiting scientists accomplishing these programs shall serve on-site at MSFC to take advantage of existing laboratory facilities and the daily opportunities for technical communications with various senior scientists.

In situ growth of metal particles on 3D urchin-like WO3 nanostructures.

PubMed

Xi, Guangcheng; Ye, Jinhua; Ma, Qiang; Su, Ning; Bai, Hua; Wang, Chao

2012-04-18

Metal/semiconductor hybrid materials of various sizes and morphologies have many applications in areas such as catalysis and sensing. Various organic agents are necessary to stabilize metal nanoparticles during synthesis, which leads to a layer of organic compounds present at the interfaces between the metal particles and the semiconductor supports. Generally, high-temperature oxidative treatment is used to remove the organics, which can extensively change the size and morphology of the particles, in turn altering their activity. Here we report a facile method for direct growth of noble-metal particles on WO(3) through an in situ redox reaction between weakly reductive WO(2.72) and oxidative metal salts in aqueous solution. This synthetic strategy has the advantages that it takes place in one step and requires no foreign reducing agents, stabilizing agents, or pretreatment of the precursors, making it a practical method for the controlled synthesis of metal/semiconductor hybrid nanomaterials. This synthetic method may open up a new way to develop metal-nanoparticle-loaded semiconductor composites. © 2012 American Chemical Society

Doping-assisted defect control in compound semiconductors

DOEpatents

Specht, Petra; Weber, Eicke R.; Weatherford, Todd Russell

2006-07-11

The present invention relates to the production of thin film epilayers of III–V and other compounds with acceptor doping wherein the acceptor thermally stabilizes the epilayer, stabilize the naturally incorporated native defect population and therewith maintain the epilayer's beneficial properties upon annealing among other advantageous effects. In particular, balanced doping in which the acceptor concentration is similar to (but does not exceed) the antisite defects in the as-grown material is shown to be particularly advantageous in providing thermal stability, high resistivity and ultrashort trapping times. In particular, MBE growth of LT-GaAs epilayers with balanced Be doping is described in detail. The growth conditions greatly enhance the materials reproducibility (that is, the yield in processed devices). Such growth techniques can be transferred to other III–V materials if the growth conditions are accurately reproduced. Materials produced herein also demonstrate advantages in reproducibility, reliability and radiation hardening.

Spatial separation of electrons and holes for enhancing the gas-sensing property of a semiconductor: ZnO/ZnSnO3 nanorod arrays prepared by a hetero-epitaxial growth

NASA Astrophysics Data System (ADS)

Wang, Ying; Gao, Peng; Sha, Linna; Chi, Qianqian; Yang, Lei; Zhang, Jianjiao; Chen, Yujin; Zhang, Milin

2018-04-01

The construction of semiconductor composites is known as a powerful method used to realize the spatial separation of electrons and the holes in them, which can result in more electrons or holes and increase the dispersion of oxygen ions ({{{{O}}}2}- and O - ) (one of the most critical factors for their gas-sensing properties) on the surface of the semiconductor gas sensor. In this work, using 1D ZnO/ZnSnO3 nanoarrays as an example, which are prepared through a hetero-epitaxial growing process to construct a chemically bonded interface, the above strategy to attain a better semiconductor gas-sensing property has been realized. Compared with single ZnSnO3 nanotubes and no-matching ZnO/ZnSnO3 nanoarrays gas sensors, it has been proven by x-ray photoelectron spectroscopy and photoluminescence spectrum examination that the as-obtained ZnO/ZnSnO3 sensor showed a greatly increased quantity of active surface electrons with exceptional responses to trace target gases and much lower optimum working temperatures (less than about 170 °C). For example, the as-obtained ZnO/ZnSnO3 sensor exhibited an obvious response and short response/recovery time (less than 10 s) towards trace H2S gas (a detection limit down to 700 ppb). The high responses and dynamic repeatability observed in these sensors reveal that the strategy based on the as-presented electron and hole separation is reliable for improving the gas-sensing properties of semiconductors.

Strain Relaxation in Si{sub 1-x}Ge{sub x} Thin Films on Si(100) Substrates: Modeling and Comparisons with Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolluri, K; Zepeda-Ruiz, L A; Murthy, C S

2005-03-22

Strained semiconductor thin films grown epitaxially on semiconductor substrates of different composition, such as Si{sub 1-x}Ge{sub x}/Si, are becoming increasingly important in modern microelectronic technologies. In this paper, we report a hierarchical computational approach for analysis of dislocation formation, glide motion, multiplication, and annihilation in Si{sub 1-x}Ge{sub x} epitaxial thin films on Si substrates. Specifically, a condition is developed for determining the critical film thickness with respect to misfit dislocation generation as a function of overall film composition, film compositional grading, and (compliant) substrate thickness. In addition, the kinetics of strain relaxation in the epitaxial film during growth or thermalmore » annealing (including post-implantation annealing) is analyzed using a properly parameterized dislocation mean-field theoretical model, which describes plastic deformation dynamics due to threading dislocation propagation. The theoretical results for Si{sub 1-x}Ge{sub x} epitaxial thin films grown on Si (100) substrates are compared with experimental measurements and are used to discuss film growth and thermal processing protocols toward optimizing the mechanical response of the epitaxial film.« less

Active bialkali photocathodes on free-standing graphene substrates

DOE PAGES

Yamaguchi, Hisato; Liu, Fangze; DeFazio, Jeffrey; ...

2017-06-01

Here, the hexagonal structure of graphene gives rise to the property of gas impermeability, motivating its investigation for a new application: protection of semiconductor photocathodes in electron accelerators. These materials are extremely susceptible to degradation in efficiency through multiple mechanisms related to contamination from the local imperfect vacuum environment of the host photoinjector. Few-layer graphene has been predicted to permit a modified photoemission response of protected photocathode surfaces, and recent experiments of single-layer graphene on copper have begun to confirm these predictions for single crystal metallic photocathodes. Unlike metallic photoemitters, the integration of an ultra-thin graphene barrier film with conventionalmore » semiconductor photocathode growth processes is not straightforward. A first step toward addressing this challenge is the growth and characterization of technologically relevant, high quantum efficiency bialkali photocathodes on ultra-thin free-standing graphene substrates. Photocathode growth on free-standing graphene provides the opportunity to integrate these two materials and study their interaction. Specifically, spectral response features and photoemission stability of cathodes grown on graphene substrates are compared to those deposited on established substrates. In addition, we observed an increase of work function for the graphene encapsulated bialkali photocathode surfaces, which is predicted by our calculations. The results provide a unique demonstration of bialkali photocathodes on free-standing substrates, and indicate promise towards our goal of fabricating high-performance graphene encapsulated photocathodes with enhanced lifetime for accelerator applications.« less

Active bialkali photocathodes on free-standing graphene substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamaguchi, Hisato; Liu, Fangze; DeFazio, Jeffrey

Here, the hexagonal structure of graphene gives rise to the property of gas impermeability, motivating its investigation for a new application: protection of semiconductor photocathodes in electron accelerators. These materials are extremely susceptible to degradation in efficiency through multiple mechanisms related to contamination from the local imperfect vacuum environment of the host photoinjector. Few-layer graphene has been predicted to permit a modified photoemission response of protected photocathode surfaces, and recent experiments of single-layer graphene on copper have begun to confirm these predictions for single crystal metallic photocathodes. Unlike metallic photoemitters, the integration of an ultra-thin graphene barrier film with conventionalmore » semiconductor photocathode growth processes is not straightforward. A first step toward addressing this challenge is the growth and characterization of technologically relevant, high quantum efficiency bialkali photocathodes on ultra-thin free-standing graphene substrates. Photocathode growth on free-standing graphene provides the opportunity to integrate these two materials and study their interaction. Specifically, spectral response features and photoemission stability of cathodes grown on graphene substrates are compared to those deposited on established substrates. In addition, we observed an increase of work function for the graphene encapsulated bialkali photocathode surfaces, which is predicted by our calculations. The results provide a unique demonstration of bialkali photocathodes on free-standing substrates, and indicate promise towards our goal of fabricating high-performance graphene encapsulated photocathodes with enhanced lifetime for accelerator applications.« less

Experiment requirements and implementation plan (Erip) for semiconductor materials growth in low-G environment

NASA Technical Reports Server (NTRS)

Crouch, R. K.; Fripp, A. L.; Debnam, W. J.; Clark, I. O.

1983-01-01

The MEA-2 A facility was used to test the effect of the low gravity environment on suppressing convective mixing in the growth of Pb(1-x)Sn(x)Te crystals. The need to eliminate convection, the furnace characteristics and operation that will be required for successful experimental implementation, and to the level that is presently known, the measured physical properties of the Pb(1-x)Sn(x)Te system were discussed. In addition, a brief background of the present and potential utilization of Pb(1-x)Sn(x)Te is given. Additional experiments are anticipated in future MEA-A, improved MEA and other dedicated materials processing in space flight apparatus.

Organo luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes

DOEpatents

Weiss, Shimon; Bruchez, Jr., Marcel; Alivisatos, Paul

2006-09-05

A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) at least one linking agent, having a first portion linked to the semiconductor nanocrystal and a second portion capable of linking to an affinity molecule. The compound is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. subsequent exposure to excitation energy will excite the semiconductor nanocrystal in the probe causing the emission of electromagnetic radiation. Further described are processes for respectively: making the luminescent semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.

Organo luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes

DOEpatents

Weiss, Shimon [Pinole, CA; Bruchez, Jr., Marcel; Alivisatos, Paul [Oakland, CA

2004-03-02

A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) at least one linking agent, having a first portion linked to the semiconductor nanocrystal and a second portion capable of linking to an affinity molecule. The compound is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Subsequent exposure to excitation energy will excite the semiconductor nanocrystal in the probe, causing the emission of electromagnetic radiation. Further described are processes for respectively: making the semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.

Organo luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes

DOEpatents

Weiss, Shimon; Bruchez, Jr., Marcel; Alivisatos, Paul

2005-08-09

A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) at least one linking agent, having a first portion linked to the semiconductor nanocrystal and a second portion capable of linking to an affinity molecule. The compound is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Subsequent exposure to excitation energy will excite the semiconductor nanocrystal in the probe causing the emission of electromagnetic radiation. Further described are processes for respectively: making the luminescent semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.

Organo luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes

DOEpatents

Weiss, Shimon; Bruchez, Jr., Marcel; Alivisatos, Paul

2002-01-01

A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) at least one linking agent, having a first portion linked to the semiconductor nanocrystal and a second portion capable of linking to an affity molecule. The compound is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Subsequent exposure to excitation energy will excite the semiconductor nanocrystal in he probe, causing the emission of electromagnetic radiation. Further described are processes for respectively: making the semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.

Semiconductor nanocrystal probes for biological applications and process for making and using such probes

DOEpatents

Weiss, Shimon; Bruchez, Marcel; Alivisatos, Paul

2014-01-28

A semiconductor nanocrystal compound and probe are described. The compound is capable of linking to one or more affinity molecules. The compound comprises (1) one or more semiconductor nanocrystals capable of, in response to exposure to a first energy, providing a second energy, and (2) one or more linking agents, having a first portion linked to the one or more semiconductor nanocrystals and a second portion capable of linking to one or more affinity molecules. One or more semiconductor nanocrystal compounds are linked to one or more affinity molecules to form a semiconductor nanocrystal probe capable of bonding with one or more detectable substances in a material being analyzed, and capable of, in response to exposure to a first energy, providing a second energy. Also described are processes for respectively: making the semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and treating materials with the probe.

Semiconductor nanocrystal probes for biological applications and process for making and using such probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weiss, Shimon; Bruchez, Marcel; Alivisatos, Paul A.

2016-12-27

A semiconductor nanocrystal compound and probe are described. The compound is capable of linking to one or more affinity molecules. The compound comprises (1) one or more semiconductor nanocrystals capable of, in response to exposure to a first energy, providing a second energy, and (2) one or more linking agents, having a first portion linked to the one or more semiconductor nanocrystals and a second portion capable of linking to one or more affinity molecules. One or more semiconductor nanocrystal compounds are linked to one or more affinity molecules to form a semiconductor nanocrystal probe capable of bonding with onemore » or more detectable substances in a material being analyzed, and capable of, in response to exposure to a first energy, providing a second energy. Also described are processes for respectively: making the semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and treating materials with the probe.« less

Rapid Thermal Processing of 3-5 Compound Semiconductors with Application to the Fabrication of Microwave Devices

DTIC Science & Technology

1988-05-01

LE i GOD~’Q~/ SOLID STATE ELECTRONICS LABORATORY STANFORD ELECTRON ICS LABORATORIES DEPARTMENT OF ELECTRICAL ENGINEERING L STANFORD UNIVERSITY...defects in the growth of subsequent layers. Test structures consisting 325 zEP-H~ PrzC~ LE of multiple layers of GaAs or alternating lay ers of GaAs...QA5) ~erhfellowship. ’J L Ho~ viand ) IF Gibtxn,. itecr Res Soc S% mp Proc 52. 15119t 36 Rapid thermal annealing of Si-implanted GaAs with

In situ control of industrial processes using laser light scattering and optical rotation

NASA Astrophysics Data System (ADS)

Mendoza Sanchez, Patricia Judith; López Echevarria, Daniel; Huerta Ruelas, Jorge Adalberto

2006-02-01

We present results of optical measurements in products or processes usually found in industrial processes, which can be used to control them. Laser light scattering was employed during semiconductor epitaxial growth by molecular beam epitaxy. With this technique, it was possible to determine growth rate, roughness and critical temperatures related to substrate degradation. With the same scattering technique, oil degradation as function of temperature was monitored for different automotive lubricants. Clear differences can be studied between monograde and multigrade oils. Optical rotation measurements as function of temperature were performed in apple juice in a pasteurization process like. Average variations related to optical rotation dependence of sugars were measured and monitored during heating and cooling process, finding a reversible behavior. As opposite behavior, sugar-protein solution was measured in a similar heating and cooling process. Final result showed a non-reversible behavior related to protein denaturation. Potential applications are discussed for metal-mechanic, electronic, food, and pharmaceutical industry. Future improvements in optical systems to make them more portable and easily implemented under typical industry conditions are mentioned.

Growth mechanism of GaAs1-xSbx ternary alloy thin film on MOCVD reactor using TMGa, TDMAAs and TDMASb

NASA Astrophysics Data System (ADS)

Suhandi, A.; Tayubi, Y. R.; Arifin, P.

2016-04-01

Metal Organic Chemical Vapor Deposition (MOCVD) is a method for growing a solid material (in the form of thin films, especially for semiconductor materials) using vapor phase metal organic sources. Studies on the growth mechanism of GaAs1-xSbx ternary alloy thin solid film in the range of miscibility-gap using metal organic sources trimethylgallium (TMGa), trisdimethylaminoarsenic (TDMAAs), and trisdimethylaminoantimony (TDMASb) on MOCVD reactor has been done to understand the physical and chemical processes involved. Knowledge of the processes that occur during alloy formation is very important to determine the couple of growth condition and growth parameters are appropriate for yield high quality GaAs1-xSbx alloy. The mechanism has been studied include decomposition of metal organic sources and chemical reactions that may occur, the incorporation of the alloy elements forming and the contaminants element that are formed in the gown thin film. In this paper presented the results of experimental data on the growth of GaAs1-xSbx alloy using Vertical-MOCVD reactor to demonstrate its potential in growing GaAs1-xSbx alloy in the range of its miscibility gap.

Growth and applications of GeSn-related group-IV semiconductor materials

PubMed Central

Zaima, Shigeaki; Nakatsuka, Osamu; Taoka, Noriyuki; Kurosawa, Masashi; Takeuchi, Wakana; Sakashita, Mitsuo

2015-01-01

We review the technology of Ge1−xSnx-related group-IV semiconductor materials for developing Si-based nanoelectronics. Ge1−xSnx-related materials provide novel engineering of the crystal growth, strain structure, and energy band alignment for realising various applications not only in electronics, but also in optoelectronics. We introduce our recent achievements in the crystal growth of Ge1−xSnx-related material thin films and the studies of the electronic properties of thin films, metals/Ge1−xSnx, and insulators/Ge1−xSnx interfaces. We also review recent studies related to the crystal growth, energy band engineering, and device applications of Ge1−xSnx-related materials, as well as the reported performances of electronic devices using Ge1−xSnx related materials. PMID:27877818

Growth and applications of GeSn-related group-IV semiconductor materials.

PubMed

Zaima, Shigeaki; Nakatsuka, Osamu; Taoka, Noriyuki; Kurosawa, Masashi; Takeuchi, Wakana; Sakashita, Mitsuo

2015-08-01

We review the technology of Ge 1- x Sn x -related group-IV semiconductor materials for developing Si-based nanoelectronics. Ge 1- x Sn x -related materials provide novel engineering of the crystal growth, strain structure, and energy band alignment for realising various applications not only in electronics, but also in optoelectronics. We introduce our recent achievements in the crystal growth of Ge 1- x Sn x -related material thin films and the studies of the electronic properties of thin films, metals/Ge 1- x Sn x , and insulators/Ge 1- x Sn x interfaces. We also review recent studies related to the crystal growth, energy band engineering, and device applications of Ge 1- x Sn x -related materials, as well as the reported performances of electronic devices using Ge 1- x Sn x related materials.

Surrogate Seeds For Growth Of Crystals

NASA Technical Reports Server (NTRS)

Shlichta, Paul J.

1989-01-01

Larger crystals of higher quality grown. Alternative method for starting growth of crystal involves use of seed crystal of different material instead of same material as solution. Intended for growing single-crystal proteins for experiments but applicable in general to growth of crystals from solutions and to growth of semiconductor or other crystals from melts.

Investigation of Low Cost Substrate Approaches for III-V Solar Cells

NASA Astrophysics Data System (ADS)

Lichty, Marlene Lydia

With the need for cleaner energy sources, which can displace fossil fuel, the solar cell industry is of particular interest due to the abundancy of the Sun. Silicon currently dominates terrestrial applications, but efficiency improvements have saturated. III-V based solar cells have reported the highest efficiencies, however, high costs due to substrates and fabrication processes have limited these devices to specialty applications, such as space. In order to reduce the cost associated with fabricating III-V semiconductor substrate material, two different approaches were taken in this work with a particular focus on making III-Vs more applicable outside of specialty applications, including InP, InAsnd Ge. Typical material characterization techniques were used to analyze the samples and processes studied in this thesis. The first process examined was the direct epitaxial growth of III-V materials by MOCVD on cheaper substrates. More specifically, the direct growth of InP and InAs on metal foils. A growth time study and surface coverage analysis was performed for the growth of InP. A characterization study was then conducted on the second process, the aluminum- induced crystallization of germanium to determine the effects this process had on the surface. Crystalline InP, InAs and Ge were successfully characterized in this work, and show promise for use in cheaper III-V alternatives to terrestrial energy solutions.

Control of Ga-oxide interlayer growth and Ga diffusion in SiO2/GaN stacks for high-quality GaN-based metal-oxide-semiconductor devices with improved gate dielectric reliability

NASA Astrophysics Data System (ADS)

Yamada, Takahiro; Watanabe, Kenta; Nozaki, Mikito; Yamada, Hisashi; Takahashi, Tokio; Shimizu, Mitsuaki; Yoshigoe, Akitaka; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

2018-01-01

A simple and feasible method for fabricating high-quality and highly reliable GaN-based metal-oxide-semiconductor (MOS) devices was developed. The direct chemical vapor deposition of SiO2 films on GaN substrates forming Ga-oxide interlayers was carried out to fabricate SiO2/GaO x /GaN stacked structures. Although well-behaved hysteresis-free GaN-MOS capacitors with extremely low interface state densities below 1010 cm-2 eV-1 were obtained by postdeposition annealing, Ga diffusion into overlying SiO2 layers severely degraded the dielectric breakdown characteristics. However, this problem was found to be solved by rapid thermal processing, leading to the superior performance of the GaN-MOS devices in terms of interface quality, insulating property, and gate dielectric reliability.

Materials Science Experiments Under Microgravity - A Review of History, Facilities, and Future Opportunities

NASA Technical Reports Server (NTRS)

Stenzel, Ch.

2012-01-01

Materials science experiments have been a key issue already since the early days of research under microgravity conditions. A microgravity environment facilitates processing of metallic and semiconductor melts without buoyancy driven convection and sedimentation. Hence, crystal growth of semiconductors, solidification of metallic alloys, and the measurement of thermo-physical parameters are the major applications in the field of materials science making use of these dedicated conditions in space. In the last three decades a large number of successful experiments have been performed, mainly in international collaborations. In parallel, the development of high-performance research facilities and the technological upgrade of diagnostic and stimuli elements have also contributed to providing optimum conditions to perform such experiments. A review of the history of materials science experiments in space focussing on the development of research facilities is given. Furthermore, current opportunities to perform such experiments onboard ISS are described and potential future options are outlined.

Twenty years of molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Cho, A. Y.

1995-05-01

The term "molecular beam epitaxy" (MBE) was first used in one of our crystal growth papers in 1970, after having conducted extensive surface physics studies in the late 1960's of the interaction of atomic and molecular beams with solid surfaces. The unique feature of MBE is the ability to prepare single crystal layers with atomic dimensional precision. MBE sets the standard for epitaxial growth and has made possible semiconductor structures that could not be fabricated with either naturally existing materials or by other crystal growth techniques. MBE led the crystal growth technologies when it prepared the first semiconductor quantum well and superlattice structures that gave unexpected and exciting electrical and optical properties. For example, the discovery of the fractional quantized Hall effect. It brought experimental quantum physics to the classroom, and practically all major universities throughout the world are now equipped with MBE systems. The fundamental principles demonstrated by the MBE growth of III-V compound semiconductors have also been applied to the growth of group IV, II-VI, metal, and insulating materials. For manufacturing, the most important criteria are uniformity, precise control of the device structure, and reproducibility. MBE has produced more lasers (3 to 5 million per month for compact disc application) than any other crystal growth technique in the world. New directions for MBE are to incorporate in-situ, real-time monitoring capabilities so that complex structures can be precisely "engineered". In the future, as environmental concerns increase, the use of toxic arsine and phosphine may be limited. Successful use of valved cracker cells for solid arsenic and phosphorus has already produced InP based injection lasers.

Strained-layer indium gallium arsenide-gallium arsenide- aluminum galium arsenide photonic devices by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Osowski, Mark Louis

With the arrival of advanced growth technologies such as molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD), research in III-V compound semiconductor photonic devices has flourished. Advances in fabrication processes have allowed the realization of high-performance quantum well lasers which emit over a wide spectral range and operate with low threshold currents. As a result, semiconductor lasers are presently employed in a wide variety of applications, including fiber-optic telecommunications, optical spectroscopy, solid-state laser pumping, and photonic integrated circuits. The work in this dissertation addresses three photonic device structures which are currently receiving a great deal of attention in the research community: integrable quantum well laser devices, distributed feedback (DFB) laser devices, and quantum wire arrays. For the realization of the integrable and integrated photonic devices described-in Chapter 2, a three-step selective-area growth technique was utilized. The selective epitaxy process was used to produce discrete buried-heterostructure Fabry Perot lasers with threshold currents as low as 2.6 mA. Based on this process, broad- spectrum edge-emitting superluminescent diodes are demonstrated which display spectral widths of over 80 nm. In addition, the monolithic integration of a multiwavelength emitter is demonstrated in which two distinct laser sources are coupled into a single output waveguide. The dissertation also describes the development of a single-growth-step ridge waveguide DFB laser. The DFB laser utilizes an asymmetric cladding waveguide structure to enhance the interaction of the optical mode with the titanium surface metal to promote single frequency emission via gain coupling. These lasers exhibit low threshold currents (11 mA), high side mode suppression ratios (50 dB), and narrow linewidths (45 kHz). In light of the substantial performance advantages of quantum well lasers relative to double heterostructure lasers, extensive efforts have been directed toward producing quantum wire systems. In view of this, the final subject of this dissertation details the fabrication and characterization of quantum wire arrays by selective-area MOCVD. The method employs a silicon dioxide grating mask with sub-micron oxide dimensions to achieve selective deposition of high-quality buried layers in the open areas of the patterned substrate. This allows the fabrication of embedded nanostructures in a single growth step, and the crystallographic nature of the growth allows for control of their lateral size. Using this process, the growth of strained InGaAs wires with a lateral dimension of less than 50 nm are obtained. Subsequent characterization by photoluminescence, scanning electron microscopy and transmission electron microscopy is also presented.

Spontaneously formed high-performance charge-transport layers of organic single-crystal semiconductors on precisely synthesized insulating polymers

NASA Astrophysics Data System (ADS)

Makita, Tatsuyuki; Sasaki, Masayuki; Annaka, Tatsuro; Sasaki, Mari; Matsui, Hiroyuki; Mitsui, Chikahiko; Kumagai, Shohei; Watanabe, Shun; Hayakawa, Teruaki; Okamoto, Toshihiro; Takeya, Jun

2017-04-01

Charge-transporting semiconductor layers with high carrier mobility and low trap-density, desired for high-performance organic transistors, are spontaneously formed as a result of thermodynamic phase separation from a blend of π-conjugated small molecules and precisely synthesized insulating polymers dissolved in an aromatic solvent. A crystal film grows continuously to the size of centimeters, with the critical conditions of temperature, concentrations, and atmosphere. It turns out that the molecular weight of the insulating polymers plays an essential role in stable film growth and interfacial homogeneity at the phase separation boundary. Fabricating the transistor devices directly at the semiconductor-insulator boundaries, we demonstrate that the mixture of 3,11-didecyldinaphtho[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene and poly(methyl methacrylate) with the optimized weight-average molecular weight shows excellent device performances. The spontaneous phase separation with a one-step fabrication process leads to a high mobility up to 10 cm2 V-1 s-1 and a low subthreshold swing of 0.25 V dec-1 even without any surface treatment such as self-assembled monolayer modifications on oxide gate insulators.

Mesoscopic Elastic Distortions in GaAs Quantum Dot Heterostructures.

PubMed

Pateras, Anastasios; Park, Joonkyu; Ahn, Youngjun; Tilka, Jack A; Holt, Martin V; Reichl, Christian; Wegscheider, Werner; Baart, Timothy A; Dehollain, Juan Pablo; Mukhopadhyay, Uditendu; Vandersypen, Lieven M K; Evans, Paul G

2018-05-09

Quantum devices formed in high-electron-mobility semiconductor heterostructures provide a route through which quantum mechanical effects can be exploited on length scales accessible to lithography and integrated electronics. The electrostatic definition of quantum dots in semiconductor heterostructure devices intrinsically involves the lithographic fabrication of intricate patterns of metallic electrodes. The formation of metal/semiconductor interfaces, growth processes associated with polycrystalline metallic layers, and differential thermal expansion produce elastic distortion in the active areas of quantum devices. Understanding and controlling these distortions present a significant challenge in quantum device development. We report synchrotron X-ray nanodiffraction measurements combined with dynamical X-ray diffraction modeling that reveal lattice tilts with a depth-averaged value up to 0.04° and strain on the order of 10 -4 in the two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure. Elastic distortions in GaAs/AlGaAs heterostructures modify the potential energy landscape in the 2DEG due to the generation of a deformation potential and an electric field through the piezoelectric effect. The stress induced by metal electrodes directly impacts the ability to control the positions of the potential minima where quantum dots form and the coupling between neighboring quantum dots.

Context-based automated defect classification system using multiple morphological masks

DOEpatents

Gleason, Shaun S.; Hunt, Martin A.; Sari-Sarraf, Hamed

2002-01-01

Automatic detection of defects during the fabrication of semiconductor wafers is largely automated, but the classification of those defects is still performed manually by technicians. This invention includes novel digital image analysis techniques that generate unique feature vector descriptions of semiconductor defects as well as classifiers that use these descriptions to automatically categorize the defects into one of a set of pre-defined classes. Feature extraction techniques based on multiple-focus images, multiple-defect mask images, and segmented semiconductor wafer images are used to create unique feature-based descriptions of the semiconductor defects. These feature-based defect descriptions are subsequently classified by a defect classifier into categories that depend on defect characteristics and defect contextual information, that is, the semiconductor process layer(s) with which the defect comes in contact. At the heart of the system is a knowledge database that stores and distributes historical semiconductor wafer and defect data to guide the feature extraction and classification processes. In summary, this invention takes as its input a set of images containing semiconductor defect information, and generates as its output a classification for the defect that describes not only the defect itself, but also the location of that defect with respect to the semiconductor process layers.

Controlled Growth of Rubrene Nanowires by Eutectic Melt Crystallization

NASA Astrophysics Data System (ADS)

Chung, Jeyon; Hyon, Jinho; Park, Kyung-Sun; Cho, Boram; Baek, Jangmi; Kim, Jueun; Lee, Sang Uck; Sung, Myung Mo; Kang, Youngjong

2016-03-01

Organic semiconductors including rubrene, Alq3, copper phthalocyanine and pentacene are crystallized by the eutectic melt crystallization. Those organic semiconductors form good eutectic systems with the various volatile crystallizable additives such as benzoic acid, salicylic acid, naphthalene and 1,3,5-trichlorobenzene. Due to the formation of the eutectic system, organic semiconductors having originally high melting point (Tm > 300 °C) are melted and crystallized at low temperature (Te = 40.8-133 °C). The volatile crystallizable additives are easily removed by sublimation. For a model system using rubrene, single crystalline rubrene nanowires are prepared by the eutectic melt crystallization and the eutectic-melt-assisted nanoimpinting (EMAN) technique. It is demonstrated that crystal structure and the growth direction of rubrene can be controlled by using different volatile crystallizable additives. The field effect mobility of rubrene nanowires prepared using several different crystallizable additives are measured and compared.

Growth and Performance of GaInP/A1GaInP Visible Light Emitting Laser-Diodes,

DTIC Science & Technology

SEMICONDUCTOR LASERS, *EPITAXIAL GROWTH, ALLOYS, LAYERS, LOW PRESSURE, PRESSURE, QUALITY, ROOM TEMPERATURE, SUBSTRATES, GALLIUM PHOSPHIDES, INDIUM PHOSPHIDES, THERMAL PROPERTIES, ENERGY GAPS, ENERGY BANDS, VAPOR PHASES.

Emission factors of air toxics from semiconductor manufacturing in Korea.

PubMed

Eom, Yun-Sung; Hong, Ji-Hyung; Lee, Suk-Jo; Lee, Eun-Jung; Cha, Jun-Seok; Lee, Dae-Gyun; Bang, Sun-Ae

2006-11-01

The development of local, accurate emission factors is very important for the estimation of reliable national emissions and air quality management. For that, this study is performed for pollutants released to the atmosphere with source-specific emission tests from the semiconductor manufacturing industry. The semiconductor manufacturing industry is one of the major sources of air toxics or hazardous air pollutants (HAPs); thus, understanding the emission characteristics of the emission source is a very important factor in the development of a control strategy. However, in Korea, there is a general lack of information available on air emissions from the semiconductor industry. The major emission sources of air toxics examined from the semiconductor manufacturing industry were wet chemical stations, coating applications, gaseous operations, photolithography, and miscellaneous devices in the wafer fabrication and semiconductor packaging processes. In this study, analyses of emission characteristics, and the estimations of emission data and factors for air toxics, such as acids, bases, heavy metals, and volatile organic compounds from the semiconductor manufacturing process have been performed. The concentration of hydrogen chloride from the packaging process was the highest among all of the processes. In addition, the emission factor of total volatile organic compounds (TVOCs) for the packaging process was higher than that of the wafer fabrication process. Emission factors estimated in this study were compared with those of Taiwan for evaluation, and they were found to be of similar level in the case of TVOCs and fluorine compounds.

Development of Room Temperature Excitonic Lasing From ZnO and MgZnO Thin Film Based Metal-Semiconductor-Metal Devices

NASA Astrophysics Data System (ADS)

Suja, Mohammad Zahir Uddin

Room temperature excitonic lasing is demonstrated and developed by utilizing metal-semiconductor-metal devices based on ZnO and MgZnO materials. At first, Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films and the best conductivity is achieved with a high hole concentration of 1.54x1018 cm-3, a low resistivity of 0.6 O cm and a moderate mobility of 6.65 cm2 V -1 s-1 at room temperature. Metal oxide semiconductor (MOS) capacitor devices have been fabricated on the Cu-doped ZnO films and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as XRD, XPS, Raman and absorption are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO. To overcome the stability issue of p-type ZnO film, alternate devices other than p-n junction has been developed. Electrically driven plasmon-exciton coupled random lasing is demonstrated by incorporating Ag nanoparticles on Cu-doped ZnO metal-semiconductor-metal (MSM) devices. Both photoluminescence and electroluminescence studies show that emission efficiencies have been enhanced significantly due to coupling between ZnO excitons and Ag surface plasmons. With the incorporation of Ag nanoparticles on ZnO MSM structures, internal quantum efficiency up to 6 times is demonstrated. Threshold current for lasing is decreased by as much as 30% while the output power is increased up to 350% at an injection current of 40 mA. A numerical simulation study reveals that hole carriers are generated in the ZnO MSM devices from impact ionization processes for subsequent plasmon-exciton coupled lasing. Our results suggest that plasmon-enhanced ZnO MSM random lasers can become a competitive candidate of efficient ultraviolet light sources. Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. In this thesis, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM) random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29 33 A/cm2 are achieved. Numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.

Optical processing for semiconductor device fabrication

NASA Technical Reports Server (NTRS)

Sopori, Bhushan L.

1994-01-01

A new technique for semiconductor device processing is described that uses optical energy to produce local heating/melting in the vicinity of a preselected interface of the device. This process, called optical processing, invokes assistance of photons to enhance interface reactions such as diffusion and melting, as compared to the use of thermal heating alone. Optical processing is performed in a 'cold wall' furnace, and requires considerably lower energies than furnace or rapid thermal annealing. This technique can produce some device structures with unique properties that cannot be produced by conventional thermal processing. Some applications of optical processing involving semiconductor-metal interfaces are described.

Solution-Processed Donor-Acceptor Polymer Nanowire Network Semiconductors For High-Performance Field-Effect Transistors

PubMed Central

Lei, Yanlian; Deng, Ping; Li, Jun; Lin, Ming; Zhu, Furong; Ng, Tsz-Wai; Lee, Chun-Sing; Ong, Beng S.

2016-01-01

Organic field-effect transistors (OFETs) represent a low-cost transistor technology for creating next-generation large-area, flexible and ultra-low-cost electronics. Conjugated electron donor-acceptor (D-A) polymers have surfaced as ideal channel semiconductor candidates for OFETs. However, high-molecular weight (MW) D-A polymer semiconductors, which offer high field-effect mobility, generally suffer from processing complications due to limited solubility. Conversely, the readily soluble, low-MW D-A polymers give low mobility. We report herein a facile solution process which transformed a lower-MW, low-mobility diketopyrrolopyrrole-dithienylthieno[3,2-b]thiophene (I) into a high crystalline order and high-mobility semiconductor for OFETs applications. The process involved solution fabrication of a channel semiconductor film from a lower-MW (I) and polystyrene blends. With the help of cooperative shifting motion of polystyrene chain segments, (I) readily self-assembled and crystallized out in the polystyrene matrix as an interpenetrating, nanowire semiconductor network, providing significantly enhanced mobility (over 8 cm2V−1s−1), on/off ratio (107), and other desirable field-effect properties that meet impactful OFET application requirements. PMID:27091315

Oriented graphene nanoribbons embedded in hexagonal boron nitride trenches

PubMed Central

Chen, Lingxiu; He, Li; Wang, Hui Shan; Wang, Haomin; Tang, Shujie; Cong, Chunxiao; Xie, Hong; Li, Lei; Xia, Hui; Li, Tianxin; Wu, Tianru; Zhang, Daoli; Deng, Lianwen; Yu, Ting; Xie, Xiaoming; Jiang, Mianheng

2017-01-01

Graphene nanoribbons (GNRs) are ultra-narrow strips of graphene that have the potential to be used in high-performance graphene-based semiconductor electronics. However, controlled growth of GNRs on dielectric substrates remains a challenge. Here, we report the successful growth of GNRs directly on hexagonal boron nitride substrates with smooth edges and controllable widths using chemical vapour deposition. The approach is based on a type of template growth that allows for the in-plane epitaxy of mono-layered GNRs in nano-trenches on hexagonal boron nitride with edges following a zigzag direction. The embedded GNR channels show excellent electronic properties, even at room temperature. Such in-plane hetero-integration of GNRs, which is compatible with integrated circuit processing, creates a gapped channel with a width of a few benzene rings, enabling the development of digital integrated circuitry based on GNRs. PMID:28276532

Organic Donor-Acceptor Complexes as Novel Organic Semiconductors.

PubMed

Zhang, Jing; Xu, Wei; Sheng, Peng; Zhao, Guangyao; Zhu, Daoben

2017-07-18

Organic donor-acceptor (DA) complexes have attracted wide attention in recent decades, resulting in the rapid development of organic binary system electronics. The design and synthesis of organic DA complexes with a variety of component structures have mainly focused on metallicity (or even superconductivity), emission, or ferroelectricity studies. Further efforts have been made in high-performance electronic investigations. The chemical versatility of organic semiconductors provides DA complexes with a great number of possibilities for semiconducting applications. Organic DA complexes extend the semiconductor family and promote charge separation and transport in organic field-effect transistors (OFETs) and organic photovoltaics (OPVs). In OFETs, the organic complex serves as an active layer across extraordinary charge pathways, ensuring the efficient transport of induced charges. Although an increasing number of organic semiconductors have been reported to exhibit good p- or n-type properties (mobilities higher than 1 or even 10 cm 2 V -1 s -1 ), critical scientific challenges remain in utilizing the advantages of existing semiconductor materials for more and wider applications while maintaining less complicated synthetic or device fabrication processes. DA complex materials have revealed new insight: their unique molecular packing and structure-property relationships. The combination of donors and acceptors could offer practical advantages compared with their unimolecular materials. First, growing crystals of DA complexes with densely packed structures will reduce impurities and traps from the self-assembly process. Second, complexes based on the original structural components could form superior mixture stacking, which can facilitate charge transport depending on the driving force in the coassembly process. Third, the effective use of organic semiconductors can lead to tunable band structures, allowing the operation mode (p- or n-type) of the transistor to be systematically controlled by changing the components. Finally, theoretical calculations based on cocrystals with unique stacking could widen our understanding of structure-property relationships and in turn help us design high-performance semiconductors based on DA complexes. In this Account, we focus on discussing organic DA complexes as a new class of semiconducting materials, including their design, growth methods, packing modes, charge-transport properties, and structure-property relationships. We have also fabricated and investigated devices based on these binary crystals. This interdisciplinary work combines techniques from the fields of self-assembly, crystallography, condensed-matter physics, and theoretical chemistry. Researchers have designed new complex systems, including donor and acceptor compounds that self-assemble in feasible ways into highly ordered cocrystals. We demonstrate that using this crystallization method can easily realize ambipolar or unipolar transport. To further improve device performance, we propose several design strategies, such as using new kinds of donors and acceptors, modulating the energy alignment of the donor (ionization potential, IP) and acceptor (electron affinity, EA) components, and extending the π-conjugated backbones. In addition, we have found that when we use molecular "doping" (2:1 cocrystallization), the charge-transport nature of organic semiconductors can be switched from hole-transport-dominated to electron-transport-dominated. We expect that the formation of cocrystals through the complexation of organic donor and acceptor species will serve as a new strategy to develop semiconductors for organic electronics with superior performances over their corresponding individual components.

Understanding and Control of Bipolar Self-Doping in Copper Nitride

PubMed Central

Fioretti, Angela N.; Schwartz, Craig P.; Vinson, John; Nordlund, Dennis; Prendergast, David; Tamboli, Adele C.; Caskey, Christopher M.; Tuomisto, Filip; Linez, Florence; Christensen, Steven T.; Toberer, Eric S.; Lany, Stephan; Zakutayev, Andriy

2016-01-01

Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu3N) is a metastable semiconductor with a solar-relevant bandgap that has been reported to exhibit bipolar doping behavior. However, deeper understanding and better control of the mechanism behind this behavior in Cu3N is currently lacking in the literature. In this work, we use combinatorial growth with a temperature gradient to demonstrate both conduction types of phase-pure, sputter-deposited Cu3N thin films. Room temperature Hall effect and Seebeck effect measurements show n-type Cu3N with an electron density of 1017 cm−3 for low growth temperature (≈ 35 °C) and p-type with a hole density between 1015 cm−3 and 1016 cm−3 for elevated growth temperatures (50 °C to 120 °C). Mobility for both types of Cu3N was ≈ 0.1 cm2/Vs to 1 cm2/V. Additionally, temperature-dependent Hall effect measurements indicate that ionized defects are an important scattering mechanism in p-type films. By combining X-ray absorption spectroscopy and first-principles defect theory, we determined that VCu defects form preferentially in p-type Cu3N while Cui defects form preferentially in n-type Cu3N; suggesting that Cu3N is a compensated semiconductor with conductivity type resulting from a balance between donor and acceptor defects. Based on these theoretical and experimental results, we propose a kinetic defect formation mechanism for bipolar doping in Cu3N, that is also supported by positron annihilation experiments. Overall, the results of this work highlight the importance of kinetic processes in the defect physics of metastable materials, and provide a framework that can be applied when considering the properties of such materials in general. PMID:27746508

Understanding and Control of Bipolar Self-Doping in Copper Nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fioretti, Angela N.; Schwartz, Craig P.; Vinson, John

2016-05-14

Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu3N) is a metastable semiconductor with a solar-relevant bandgap that has been reported to exhibit bipolar doping behavior. However, deeper understanding and better control of the mechanism behind this behavior in Cu3N is currently lacking in the literature. In this work, we use combinatorial growth with a temperature gradient to demonstrate both conduction types of phase-pure, sputter-deposited Cu3N thin films. Room temperature Hall effect and Seebeck effect measurements show n-type Cu3N with 1017 electrons/cm3 for low growth temperature (approximately 35more » degrees C) and p-type with 1015 holes/cm3-1016 holes/cm3 for elevated growth temperatures (50 degrees C-120 degrees C). Mobility for both types of Cu3N was approximately 0.1 cm2/Vs-1 cm2/Vs. Additionally, temperature-dependent Hall effect measurements indicate that ionized defects are an important scattering mechanism in p-type films. By combining X-ray absorption spectroscopy and first-principles defect theory, we determined that VCu defects form preferentially in p-type Cu3N, while Cui defects form preferentially in n-type Cu3N, suggesting that Cu3N is a compensated semiconductor with conductivity type resulting from a balance between donor and acceptor defects. Based on these theoretical and experimental results, we propose a kinetic defectformation mechanism for bipolar doping in Cu3N that is also supported by positron annihilation experiments. Overall, the results of this work highlight the importance of kinetic processes in the defect physics of metastable materials and provide a framework that can be applied when considering the properties of such materials in general.« less

Analysis of channel confined selective area growth in evolutionary growth of GaN on SiO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leung, Benjamin; Tsai, Miao-Chan; Song, Jie

2015-09-01

Here, we analyze the chemical vapor deposition of semiconductor crystals by selective area growth in a non-planar geometry. Specifically, the growth process in laterally and vertically confined masks forming single-crystal GaN on SiO2 by metal-organic chemical vapor deposition is considered in detail. A textured AlN seed is used to initiate growth of oriented GaN selectively through the mask, allowing the reduction of degrees of freedom by the evolutionary grain selection process. As shown by measurements of growth rates within the mask, the sub micron length scale of the channel opening is comparable to the mean free path of precursors inmore » the gas phase, resulting in transport characteristics that can be described by an intermediate flow regime between continuum and free-molecular. Mass transport is modeled through kinetic theory to explain the growth rate enhancements of more than a factor of two by changes in reactor pressure. The growth conditions that enable the modification of nucleation density within the channel are then discussed, and are measured by electron-back scatter diffraction of the nucleated grains on the AlN seed. Finally, the selectivity behavior using the low fill factor masks needed in these configurations has been optimized by control of precursor flow rates and the H2 enhanced etching of the polycrystalline GaN nuclei.« less

Quantification Of 4H- To 3C-Polymorphism In Silicon Carbide (SiC) Epilayers And An Investigation Of Recombination-Enhanced Dislocation Motion In SiC By Optical Emission Microscopy (Oem) Techniques

NASA Technical Reports Server (NTRS)

Speer, Kevin M.

2004-01-01

Environments that impose operational constraints on conventional silicon-(Si) based semiconductor devices frequently appear in military- and space-grade applications. These constraints include high temperature, high power, and high radiation environments. Silicon carbide (SiC), an alternative type of semiconductor material, has received abundant research attention in the past few years, owing to its radiation-hardened properties as well as its capability to withstand high temperatures and power levels. However, the growth and manufacture of SiC devices is still comparatively immature, and there are severe limitations in present crystal growth and device fabrication processes. Among these limitations is a variety of crystal imperfections known as defects. These imperfections can be point defects (e.g., vacancies and interstitials), line defects (e.g., edge and screw dislocations), or planar defects (e.g., stacking faults and double-positioning boundaries). All of these defects have been experimentally shown to be detrimental to the performance of electron devices made from SiC. As such, it is imperative that these defects are significantly reduced in order for SiC devices to become a viable entity in the electronics world. The NASA Glenn High Temperature Integrated Electronics & Sensors Team (HTIES) is working to identify and eliminate these defects in SiC by implementing improved epitaxial crystal growth procedures. HTIES takes two-inch SiC wafers and etches patterns, producing thousands of mesas into each wafer. Crystal growth is then carried out on top of these mesas in an effort to produce films of improved quality-resulting in electron devices that demonstrate superior performance-as well as fabrication processes that are cost-effective, reliable, and reproducible. In this work, further steps are taken to automate HTIES' SiC wafer inspection system. National Instruments LabVIEW image processing and pattern recognition routines are developed that are capable of quantifying and mapping defects on both the substrate and mesa surfaces, and of quantifying polymorphic changes in the grown materials. In addition, an optical emission microscopy (OEM) system is developed that will facilitate comprehensive study of recombination-enhanced dislocation motion (REDM).

Method of physical vapor deposition of metal oxides on semiconductors

DOEpatents

Norton, David P.

2001-01-01

A process for growing a metal oxide thin film upon a semiconductor surface with a physical vapor deposition technique in a high-vacuum environment and a structure formed with the process involves the steps of heating the semiconductor surface and introducing hydrogen gas into the high-vacuum environment to develop conditions at the semiconductor surface which are favorable for growing the desired metal oxide upon the semiconductor surface yet is unfavorable for the formation of any native oxides upon the semiconductor. More specifically, the temperature of the semiconductor surface and the ratio of hydrogen partial pressure to water pressure within the vacuum environment are high enough to render the formation of native oxides on the semiconductor surface thermodynamically unstable yet are not so high that the formation of the desired metal oxide on the semiconductor surface is thermodynamically unstable. Having established these conditions, constituent atoms of the metal oxide to be deposited upon the semiconductor surface are directed toward the surface of the semiconductor by a physical vapor deposition technique so that the atoms come to rest upon the semiconductor surface as a thin film of metal oxide with no native oxide at the semiconductor surface/thin film interface. An example of a structure formed by this method includes an epitaxial thin film of (001)-oriented CeO.sub.2 overlying a substrate of (001) Ge.

Growth of large aluminum nitride single crystals with thermal-gradient control

DOEpatents

Bondokov, Robert T; Rao, Shailaja P; Gibb, Shawn Robert; Schowalter, Leo J

2015-05-12

In various embodiments, non-zero thermal gradients are formed within a growth chamber both substantially parallel and substantially perpendicular to the growth direction during formation of semiconductor crystals, where the ratio of the two thermal gradients (parallel to perpendicular) is less than 10, by, e.g., arrangement of thermal shields outside of the growth chamber.

Growth of large aluminum nitride single crystals with thermal-gradient control

DOEpatents

Bondokov, Robert T.; Rao, Shailaja P.; Schowalter, Leo J.

2017-02-28

In various embodiments, non-zero thermal gradients are formed within a growth chamber both substantially parallel and substantially perpendicular to the growth direction during formation of semiconductor crystals, where the ratio of the two thermal gradients (parallel to perpendicular) is less than 10, by, e.g., arrangement of thermal shields outside of the growth chamber.

Biochips: A fruitful product of solid state physics and molecular biology

NASA Astrophysics Data System (ADS)

Mendoza-Alvarez, Julio G.

1998-08-01

The application of the standard high resolution photolithography techniques used in the semiconductor device industry to the growth of a chain of nucleotides with a precise and well known sequence, has made possible the fabrication of a new kind of device, the so called biochips. At the National Polytechnic Institute in Mexico we have joined a multidisciplinary scientific group, and we are in the process of developing the technical capabilities in order to set up a processing lab to fabricate biochips focused to very specific applications in the area of cancer detection. We present here the main lines along which this project is being developed.

Investigating Processes of Materials Formation via Liquid Phase and Cryogenic TEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Yoreo, James J.; Sommerdijk, Nico

2016-06-14

The formation of materials in solutions is a widespread phenomenon in synthetic, biological and geochemical systems, occurring through dynamic processes of nucleation, self-assembly, crystal growth, and coarsening. The recent advent of liquid phase TEM and advances in cryogenic TEM are transforming our understanding of these phenomena by providing new insights into the underlying physical and chemical mechanisms. The techniques have been applied to metallic and semiconductor nanoparticles, geochemical and biological minerals, electrochemical systems, macromolecular complexes, and selfassembling systems, both organic and inorganic. New instrumentation and methodologies currently on the horizon promise new opportunities for advancing the science of materials synthesis.

ICCG-10: Tenth International Conference on Crystal Growth. Oral presentation abstracts

NASA Technical Reports Server (NTRS)

1992-01-01

Oral presentation abstracts from the tenth International Conference on Crystal Growth (ICCG) (Aug. 16-21, 1992) are provided. Topics discussed at the conference include superconductors, semiconductors, nucleation, crystal growth mechanisms, and laser materials. Organizing committees, ICCG advisory board and officers, and sponsors of the conference are also included.

Effect of Pentacene-dielectric Affinity on Pentacene Thin Film Growth Morphology in Organic Field-effect Transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

S Kim; M Jang; H Yang

2011-12-31

Organic field-effect transistors (OFETs) are fabricated by depositing a thin film of semiconductor on the functionalized surface of a SiO{sub 2} dielectric. The chemical and morphological structures of the interface between the semiconductor and the functionalized dielectric are critical for OFET performance. We have characterized the effect of the affinity between semiconductor and functionalized dielectric on the properties of the semiconductor-dielectric interface. The crystalline microstructure/nanostructure of the pentacene semiconductor layers, grown on a dielectric substrate that had been functionalized with either poly(4-vinyl pyridine) or polystyrene (to control hydrophobicity), and grown under a series of substrate temperatures and deposition rates, weremore » characterized by X-ray diffraction, photoemission spectroscopy, and atomic force microscopy. By comparing the morphological features of the semiconductor thin films with the device characteristics (field-effect mobility, threshold voltage, and hysteresis) of the OFET devices, the effect of affinity-driven properties on charge modulation, charge trapping, and charge carrier transport could be described.« less

A Chebyshev Collocation Method for Moving Boundaries, Heat Transfer, and Convection During Directional Solidification

NASA Technical Reports Server (NTRS)

Zhang, Yiqiang; Alexander, J. I. D.; Ouazzani, J.

1994-01-01

Free and moving boundary problems require the simultaneous solution of unknown field variables and the boundaries of the domains on which these variables are defined. There are many technologically important processes that lead to moving boundary problems associated with fluid surfaces and solid-fluid boundaries. These include crystal growth, metal alloy and glass solidification, melting and name propagation. The directional solidification of semi-conductor crystals by the Bridgman-Stockbarger method is a typical example of such a complex process. A numerical model of this growth method must solve the appropriate heat, mass and momentum transfer equations and determine the location of the melt-solid interface. In this work, a Chebyshev pseudospectra collocation method is adapted to the problem of directional solidification. Implementation involves a solution algorithm that combines domain decomposition, finite-difference preconditioned conjugate minimum residual method and a Picard type iterative scheme.

Semiconductor photoelectrochemistry

NASA Technical Reports Server (NTRS)

Buoncristiani, A. M.; Byvik, C. E.

1983-01-01

Semiconductor photoelectrochemical reactions are investigated. A model of the charge transport processes in the semiconductor, based on semiconductor device theory, is presented. It incorporates the nonlinear processes characterizing the diffusion and reaction of charge carriers in the semiconductor. The model is used to study conditions limiting useful energy conversion, specifically the saturation of current flow due to high light intensity. Numerical results describing charge distributions in the semiconductor and its effects on the electrolyte are obtained. Experimental results include: an estimate rate at which a semiconductor photoelectrode is capable of converting electromagnetic energy into chemical energy; the effect of cell temperature on the efficiency; a method for determining the point of zero zeta potential for macroscopic semiconductor samples; a technique using platinized titanium dioxide powders and ultraviolet radiation to produce chlorine, bromine, and iodine from solutions containing their respective ions; the photoelectrochemical properties of a class of layered compounds called transition metal thiophosphates; and a technique used to produce high conversion efficiency from laser radiation to chemical energy.

Water-Vapor-Mediated Close-Spaced Vapor Transport Growth of Epitaxial Gallium Indium Phosphide Films on Gallium Arsenide Substrates

DOE PAGES

Greenaway, Ann L.; Bachman, Benjamin F.; Boucher, Jason W.; ...

2018-01-12

Ga 1–xIn xP is a technologically important III–V ternary semiconductor widely utilized in commercial and record-efficiency solar cells. We report the growth of Ga 1–xIn xP by water-vapor-mediated close-spaced vapor transport. Because growth of III–V semiconductors in this system is controlled by diffusion of metal oxide species, we find that congruent transport from the mixed powder source requires complete annealing to form a single alloy phase. Growth from a fully alloyed source at water vapor concentrations of ~7000 ppm in H 2 at 850 °C affords smooth films with electron mobility of 1070 cm 2 V –1 s –1 andmore » peak internal quantum efficiency of ~90% for carrier collection in a nonaqueous photoelectrochemical test cell.« less

Water-Vapor-Mediated Close-Spaced Vapor Transport Growth of Epitaxial Gallium Indium Phosphide Films on Gallium Arsenide Substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenaway, Ann L.; Bachman, Benjamin F.; Boucher, Jason W.

Ga 1–xIn xP is a technologically important III–V ternary semiconductor widely utilized in commercial and record-efficiency solar cells. We report the growth of Ga 1–xIn xP by water-vapor-mediated close-spaced vapor transport. Because growth of III–V semiconductors in this system is controlled by diffusion of metal oxide species, we find that congruent transport from the mixed powder source requires complete annealing to form a single alloy phase. Growth from a fully alloyed source at water vapor concentrations of ~7000 ppm in H 2 at 850 °C affords smooth films with electron mobility of 1070 cm 2 V –1 s –1 andmore » peak internal quantum efficiency of ~90% for carrier collection in a nonaqueous photoelectrochemical test cell.« less

Crystal growth of device quality GaAs in space

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Lagowski, J.

1985-01-01

The present program has been aimed at solving the fundamental and technological problems associated with Crystal Growth of Device Quality in Space. The initial stage of the program was devoted strictly to ground-based research. The unsolved problems associated with the growth of bulk GaAs in the presence of gravitational forces were explored. Reliable chemical, structural and electronic characterization methods were developed which would permit the direct relation of the salient materials parameters (particularly those affected by zero gravity conditions) to the electronic characteristics of single crystal GaAs, in turn to device performance. These relationships are essential for the development of optimum approaches and techniques. It was concluded that the findings on elemental semiconductors Ge and Si regarding crystal growth, segregation, chemical composition, defect interactions, and materials properties-electronic properties relationships are not necessarily applicable to GaAs (and to other semiconductor compounds). In many instances totally unexpected relationships were found to prevail.

Organo Luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes

DOEpatents

Weiss, Shimon; Bruchez, Jr., Marcel; Alivisatos, Paul

1999-01-01

A luminescent semiconductor nanocrystal compound is described which is capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation (luminescing) in a narrow wavelength band and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source (of narrow or broad bandwidth) or a particle beam; and (2) at least one linking agent, having a first portion linked to the semiconductor nanocrystal and a second portion capable of linking to an affinity molecule. The luminescent semiconductor nanocrystal compound is linked to an affinity molecule to form an organo luminescent semiconductor nanocrystal probe capable of bonding with a detectable substance in a material being analyzed, and capable of emitting electromagnetic radiation in a narrow wavelength band and/or absorbing, scattering, or diffracting energy when excited by an electromagnetic radiation source (of narrow or broad bandwidth) or a particle beam. The probe is stable to repeated exposure to light in the presence of oxygen and/or other radicals. Further described is a process for making the luminescent semiconductor nanocrystal compound and for making the organo luminescent semiconductor nanocrystal probe comprising the luminescent semiconductor nanocrystal compound linked to an affinity molecule capable of bonding to a detectable substance. A process is also described for using the probe to determine the presence of a detectable substance in a material.

Evolutionary process development towards next generation crystalline silicon solar cells : a semiconductor process toolbox application

NASA Astrophysics Data System (ADS)

John, J.; Prajapati, V.; Vermang, B.; Lorenz, A.; Allebe, C.; Rothschild, A.; Tous, L.; Uruena, A.; Baert, K.; Poortmans, J.

2012-08-01

Bulk crystalline Silicon solar cells are covering more than 85% of the world's roof top module installation in 2010. With a growth rate of over 30% in the last 10 years this technology remains the working horse of solar cell industry. The full Aluminum back-side field (Al BSF) technology has been developed in the 90's and provides a production learning curve on module price of constant 20% in average. The main reason for the decrease of module prices with increasing production capacity is due to the effect of up scaling industrial production. For further decreasing of the price per wattpeak silicon consumption has to be reduced and efficiency has to be improved. In this paper we describe a successive efficiency improving process development starting from the existing full Al BSF cell concept. We propose an evolutionary development includes all parts of the solar cell process: optical enhancement (texturing, polishing, anti-reflection coating), junction formation and contacting. Novel processes are benchmarked on industrial like baseline flows using high-efficiency cell concepts like i-PERC (Passivated Emitter and Rear Cell). While the full Al BSF crystalline silicon solar cell technology provides efficiencies of up to 18% (on cz-Si) in production, we are achieving up to 19.4% conversion efficiency for industrial fabricated, large area solar cells with copper based front side metallization and local Al BSF applying the semiconductor toolbox.

Hole-cyclotron instability in semiconductor quantum plasmas

NASA Astrophysics Data System (ADS)

Areeb, F.; Rasheed, A.; Jamil, M.; Siddique, M.; Sumera, P.

2018-01-01

The excitation of electrostatic hole-cyclotron waves generated by an externally injected electron beam in semiconductor plasmas is examined using a quantum hydrodynamic model. The quantum effects such as tunneling potential, Fermi degenerate pressure, and exchange-correlation potential are taken care of. The growth rate of the wave is analyzed on varying the parameters normalized by hole-plasma frequency, like the angle θ between propagation vector and B0∥z ̂ , speed of the externally injected electron beam v0∥k , thermal temperature of the electron beam τ, external magnetic field B0∥z ̂ that modifies the hole-cyclotron frequency, and finally, the semiconductor electron number density. The instability of the hole-cyclotron wave seeks its applications in semiconductor devices.

Gordon Research Conference on Crystal Growth (1990)

DTIC Science & Technology

1990-04-01

Labs, MH) 14. Cox Vapor Levitation Epitaxy of Quantum Wires and Wire-like Structures Using Laterally Propagating Surface Steps. (Bellcore, Red Bank) 15...introduced many new aspects of crystal growth, including strained layer superlattices, quantum cluster growth, and vertical zone melting of GaAs...Films 2. E. Bauser Semiconductor Liquid Phase Epitaxy: Growth and Properties of Layers and Heterostructures 3. M. L. Steigerwald Growth of Quantum

Semiconductor devices for optical communications in 1 micron band of wavelength. [gallium indium arsenide phosphide lasers and diodes

NASA Technical Reports Server (NTRS)

Suematsu, Y.; Iga, K.

1980-01-01

Crystal growth and the characteristics of semiconductor lasers and diodes for the long wavelength band used in optical communications are examined. It is concluded that to utilize the advantages of this band, it is necessary to have a large scale multiple wavelength communication, along with optical cumulative circuits and optical exchangers.

Silicon carbide semiconductor technology for high temperature and radiation environments

NASA Technical Reports Server (NTRS)

Matus, Lawrence G.

1993-01-01

Viewgraphs on silicon carbide semiconductor technology and its potential for enabling electronic devices to function in high temperature and high radiation environments are presented. Topics covered include silicon carbide; sublimation growth of 6H-SiC boules; SiC chemical vapor deposition reaction system; 6H silicon carbide p-n junction diode; silicon carbide MOSFET; and silicon carbide JFET radiation response.

40 CFR 63.7182 - What parts of my facility does this subpart cover?

Code of Federal Regulations, 2011 CFR

2011-07-01

... CATEGORIES (CONTINUED) National Emission Standards for Hazardous Air Pollutants for Semiconductor... manufactures semiconductors. (b) An affected source subject to this subpart is the collection of all semiconductor manufacturing process units used to manufacture p-type and n-type semiconductors and active solid...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahal, Rajendra P.; Bhat, Ishwara B.; Chow, Tat-Sing

Methods for facilitating fabricating semiconductor structures are provided which include: providing a multilayer structure including a semiconductor layer, the semiconductor layer including a dopant and having an increased conductivity; selectively increasing, using electrochemical processing, porosity of the semiconductor layer, at least in part, the selectively increasing porosity utilizing the increased conductivity of the semiconductor layer; and removing, at least in part, the semiconductor layer with the selectively increased porosity from the multilayer structure. By way of example, the selectively increasing porosity may include selectively, anodically oxidizing, at least in part, the semiconductor layer of the multilayer structure.

The relationship between spontaneous abortion and female workers in the semiconductor industry.

PubMed

Kim, Heechan; Kwon, Ho-Jang; Rhie, Jeongbae; Lim, Sinye; Kang, Yun-Dan; Eom, Sang-Yong; Lim, Hyungryul; Myong, Jun-Pyo; Roh, Sangchul

2017-01-01

This study investigated the relationship between job type and the risk for spontaneous abortion to assess the reproductive toxicity of female workers in the semiconductor industry. A questionnaire survey was administered to current female workers of two semiconductor manufacturing plants in Korea. We included female workers who became pregnant at least 6 months after the start of their employment with the company. The pregnancy outcomes of 2,242 female workers who experienced 4,037 pregnancies were investigated. Personnel records were used to assign the subjects to one of three groups: fabrication process workers, packaging process workers, and clerical workers. To adjust for within-person correlations between pregnancies, a generalized estimating equation was used. The logistic regression analysis was limited to the first pregnancy after joining the company to satisfy the assumption of independence among pregnancies. Moreover, we stratified the analysis by time period (pregnancy in the years prior to 2008 vs. after 2009) to reflect differences in occupational exposure based on semiconductor production periods. The risk for spontaneous abortion in female semiconductor workers was not significantly higher for fabrication and packaging process workers than for clerical workers. However, when we stratified by time period, the odds ratio for spontaneous abortion was significantly higher for packaging process workers who became pregnant prior to 2008 when compared with clerical workers (odds ratio: 2.21; 95% confidence interval: 1.01-4.81). When examining the pregnancies of female semiconductor workers that occurred prior to 2008, packaging process workers showed a significantly higher risk for spontaneous abortions than did clerical workers. The two semiconductor production periods in our study (prior to 2008 vs. after 2009) had different automated processes, chemical exposure levels, and working environments. Thus, the conditions prior to 2008 may have increased the risk for spontaneous abortions in packaging process workers in the semiconductor industry.

Reactor design rules for GaN epitaxial layer growths on sapphire in metal-organic chemical vapour deposition

NASA Astrophysics Data System (ADS)

Kim, Keunjoo; Noh, Sam Kyu

2000-08-01

The thermal process of the growth of GaN-based semiconductors was analysed for two home-made horizontal reactors. The reactors were designed to make the ammonia gas flow in the opposite direction to the main gas flow. For two horizontal reactors different in dimension, the low Reynolds numbers of Re = 2.94 and 4.15 were chosen for stable laminar flow and the Rayleigh numbers governing the heat convection were optimized to the values of Ra = 6.0 and 76.2, respectively. The qualities of GaN and InGaN films were characterized by Hall effect measurement, x-ray diffraction and photoluminescence and compared with respect to the reactor dependency.

Los Alamos Discovers Super Efficient Solar Using Perovskite Crystals

ScienceCinema

Mohite, Aditya; Nie, Wanyi

2018-05-11

State-of-the-art photovoltaics using high-purity, large-area, wafer-scale single-crystalline semiconductors grown by sophisticated, high temperature crystal-growth processes offer promising routes for developing low-cost, solar-based clean global energy solutions for the future. Solar cells composed of the recently discovered material organic-inorganic perovskites offer the efficiency of silicon, yet suffer from a variety of deficiencies limiting the commercial viability of perovskite photovoltaic technology. In research to appear in Science, Los Alamos National Laboratory researchers reveal a new solution-based hot-casting technique that eliminates these limitations, one that allows for the growth of high-quality, large-area, millimeter-scale perovskite crystals and demonstrates that highly efficient and reproducible solar cells with reduced trap assisted recombination can be realized.

Crystal Growth of Device Quality Gaas in Space

NASA Technical Reports Server (NTRS)

Gatos, H. C.

1985-01-01

The GaAs research evolves about these key thrust areas. The overall program combines: (1) studies of crystal growth on novel approaches to engineering of semiconductor material (i.e., GaAs and related compounds); (2) investigation and correlation of materials properties and electronic characteristics on a macro- and microscale; and (3) investigation of electronic properties and phenomena controlling device applications and device performance. This effort is aimed at the essential ground-based program which would insure successful experimentation with and eventually processing of GaAs in near zero gravity environment. It is believed that this program addresses in a unique way materials engineering aspects which bear directly on the future exploitation of the potential of GaAs and related materials in device and systems applications.

760 nm high-performance VCSEL growth and characterization

NASA Astrophysics Data System (ADS)

Rinaldi, Fernando; Ostermann, Johannes M.; Kroner, Andrea; Riedl, Michael C.; Michalzik, Rainer

2006-04-01

High-performance vertical-cavity surface-emitting lasers (VCSELs) with an emission wavelength of approximately 764 nm are demonstrated. This wavelength is very attractive for oxygen sensing. Low threshold currents, high optical output power, single-mode operation, and stable polarization are obtained. Using the surface relief technique and in particular the grating relief technique, we have increased the single-mode output power to more than 2.5mW averaged over a large device quantity. The laser structure was grown by molecular beam epitaxy (MBE) on GaAs (100)-oriented substrates. The devices are entirely based on the AlGaAs mixed compound semiconductor material system. The growth process, the investigations of the epitaxial material together with the device fabrication and characterization are discussed in detail.

Growth studies of CVD-MBE by in-situ diagnostics

NASA Astrophysics Data System (ADS)

Maracas, George N.; Steimle, Timothy C.

1992-10-01

This is the final technical report for the three year DARPA-URI program 'Growth Studies of CVD-MBE by in-situ Diagnostics'. The goals of the program were to develop non-invasive, real time epitaxial growth monitoring techniques and combine them to gain an understanding of processes that occur during MBE growth from gas sources. We have adapted these techniques to a commercially designed gas source MBE system (Vacuum Generators Inc.) to facilitate technology transfer out of the laboratory into industrial environments. The in-situ measurement techniques of spectroscopic ellipsometry (SE) and laser induced fluorescence (LIF) have been successfully implemented to monitor the optical and chemical properties of the growing epitaxial film and the gas phase reactants. The ellipsometer was jointly developed with the J. Woolam Co. and has become a commercial product. The temperature dependence of group 3 and 5 desorption from GaAs and InP has been measured as well as the incident effusion cell fluxes. The temporal evolution of the growth has also been measured both by SE and LIF to show the smoothing of heterojunction surfaces during growth interruption. Complicated microcavity optical device structures have been monitored by ellipsometry in real time to improve device quality. This data has been coupled with the structural information obtained from reflection high energy electron diffraction (RHEED) to understand the growth processes in binary and ternary bulk 3-5 semiconductors and heterojunctions.

Stable Defects in Semiconductor Nanowires.

PubMed

Sanchez, A M; Gott, J A; Fonseka, H A; Zhang, Y; Liu, H; Beanland, R

2018-05-09

Semiconductor nanowires are commonly described as being defect-free due to their ability to expel mobile defects with long-range strain fields. Here, we describe previously undiscovered topologically protected line defects with null Burgers vector that, unlike dislocations, are stable in nanoscale crystals. We analyze the defects present in semiconductor nanowires in regions of imperfect crystal growth, i.e., at the nanowire tip formed during consumption of the droplet in self-catalyzed vapor-liquid-solid growth and subsequent vapor-solid shell growth. We use a form of the Burgers circuit method that can be applied to multiply twinned material without difficulty. Our observations show that the nanowire microstructure is very different from bulk material, with line defects either (a) trapped by locks or other defects, (b) arranged as dipoles or groups with a zero total Burgers vector, or (c) have a zero Burgers vector. We find two new line defects with a null Burgers vector, formed from the combination of partial dislocations in twinned material. The most common defect is the three-monolayer high twin facet with a zero Burgers vector. Studies of individual nanowires using cathodoluminescence show that optical emission is quenched in defective regions, showing that they act as strong nonradiative recombination centers.

Design and development of SiGe based near-infrared photodetectors

NASA Astrophysics Data System (ADS)

Zeller, John W.; Puri, Yash R.; Sood, Ashok K.; McMahon, Shane; Efsthadiatis, Harry; Haldar, Pradeep; Dhar, Nibir K.

2014-10-01

Near-infrared (NIR) sensors operating at room temperatures are critical for a variety of commercial and military applications including detecting mortar fire and muzzle flashes. SiGe technology offers a low-cost alternative to conventional IR sensor technologies such as InGaAs, InSb, and HgCdTe for developing NIR micro-sensors that will not require any cooling and can operate with high bandwidths and comparatively low dark currents. Since Ge has a larger thermal expansion coefficient than Si, tensile strain may be incorporated into detector devices during the growth process, enabling an extended operating wavelength range above 1600 nm. SiGe based pin photodetectors have advantages of high stability, low noise, and high responsivity compared to metal-semiconductor-metal (MSM) devices. We have developed a process flow and are fabricating SiGe detector devices on 12" (300 mm) silicon wafers in order to take advantage of high throughput, large-area leading-edge silicon based CMOS technology that provides small feature sizes with associated device cost/density scaling advantages. The fabrication of the detector devices is facilitated by a two-step growth process incorporating initial low temperature growth of Ge/SiGe to form a thin strain-relaxed layer, followed by high temperature growth to deposit a thicker absorbing film, and subsequent high temperature anneal. This growth process is designed to effectively reduce dark current and enhance detector performance by reducing the number of defects and threading dislocations which form recombination centers during the growth process. Various characterization techniques have been employed to determine the properties of the epitaxially deposited Ge/SiGe layers, and the corresponding results are discussed.

Surface and Interface Engineering of Organometallic and Two Dimensional Semiconductor

NASA Astrophysics Data System (ADS)

Park, Jun Hong

For over half a century, inorganic Si and III-V materials have led the modern semiconductor industry, expanding to logic transistor and optoelectronic applications. However, these inorganic materials have faced two different fundamental limitations, flexibility for wearable applications and scaling limitation as logic transistors. As a result, the organic and two dimensional have been studied intentionally for various fields. In the present dissertation, three different studies will be presented with followed order; (1) the chemical response of organic semiconductor in NO2 exposure. (2) The surface and stability of WSe2 in ambient air. (3) Deposition of dielectric on two dimensional materials using organometallic seeding layer. The organic molecules rely on the van der Waals interaction during growth of thin films, contrast to covalent bond inorganic semiconductors. Therefore, the morphology and electronic property at surface of organic semiconductor in micro scale is more sensitive to change in gaseous conditions. In addition, metal phthalocyanine, which is one of organic semiconductor materials, change their electronic property as reaction with gaseous analytes, suggesting as potential chemical sensing platforms. In the present part, the growth behavior of metal phthalocyanine and surface response to gaseous condition will be elucidated using scanning tunneling microscopy (STM). In second part, the surface of layered transition metal dichalcogenides and their chemical response to exposure ambient air will be investigated, using STM. Layered transition metal dichalcogenides (TMDs) have attracted widespread attention in the scientific community for electronic device applications because improved electrostatic gate control and suppression of short channel leakage resulted from their atomic thin body. To fabricate the transistor based on TMDs, TMDs should be exposed to ambient conditions, while the effect of air exposure has not been understood fully. In this part, the effect of ambient air on TMDs will be investigated and partial oxidation of TMDs. In the last part, uniform deposition of dielectric layers on 2D materials will be presented, employing organic seedling layer. Although 2D materials have been expected as next generation semiconductor platform, direct deposition of dielectric is still challenging and induces leakage current commonly, because inertness of their surface resulted from absent of dangling bond. Here, metal phthalocyanine monolayer (ML) is employed as seedling layers and the growth of atomic layer deposition (ALD) dielectric is investigated in each step using STM.

ICCG-10: Tenth International Conference on Crystal Growth. Poster presentation abstracts

NASA Technical Reports Server (NTRS)

1992-01-01

Poster presentation abstracts from the tenth International Conference on Crystal Growth (ICCG) (Aug. 16-21, 1992) are provided. Topics discussed at the conference include crystal growth mechanisms, superconductors, semiconductors, laser materials, optical materials, and biomaterials. Organizing committees, ICCG advisory board and officers, and sponsors of the conference are also included.

Growth of Solid Solution Crystals

NASA Technical Reports Server (NTRS)

Lehoczky, S. L.; Szofran, F. R.; Holland, L. R.

1985-01-01

The major objective of this program is to determine the conditions under which single crystals of solid solutions can be grown from the melt in a Bridgman configuration with a high degree of chemical homogeneity. The central aim is to assess the role of gravity in the growth process and to explore the possible advantages for growth in the absence of gravity. The alloy system being investigated is the solid solution semiconductor with x-values appropriate for infrared detector applications in Hg sub (1-x) Cd sub x Te the 8 to 14 micro m wavelength region. Both melt and Te-solvent growth are being considered. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. Experimental facilities have been established for the purification, casting, and crystal growth of the alloy system. Facilities have been also established for the metallurgical, compositional, electric and optical characterization of the alloys. Crystals are being grown by the Bridgman-Stockbarger method and are analyzed by various experimental techniques to evaluate the effects of growth conditions on the longitudinal and radial compositional variations and defect densities in the crystals.

Surface processes in OMVPE the frontiers

NASA Astrophysics Data System (ADS)

Stringfellow, G. B.; Shurtleff, J. K.; Lee, R. T.; Fetzer, C. M.; Jun, S. W.

2000-12-01

Surface processes have long been known to be an important part of any epitaxial growth process. These processes are closely linked to the surface structure. However, until recently, the surface structure and the surface processes were difficult to study experimentally for conventional vapor-phase epitaxy (VPE) and liquid-phase epitaxy. Recently, optical techniques such as surface photo absorption (SPA) have been developed to the point that they give useful information about the surface reconstruction in situ during organometallic vapor-phase epitaxial (OMVPE) growth. Thus, they can in many cases be used to monitor the surface processes. A powerful method for controlling the surface structure during epitaxial growth using surfactants has recently emerged. This work describes the use of the surfactants Te, a donor, and As, Sb, and Bi, elements that are isoelectronic with P, on the properties of GaInP grown by OMVPE. These surfactants are found to significantly affect the microscopic arrangement of Ga and In atoms in the bulk solid by effecting a change in the surface structure. CuPt ordering is ubiquitous in III/V semiconductor alloys. It is significant because of the dependence of bandgap energy on the degree of order. The CuPt structure is formed due to the strain induced by the formation of [ 1¯ 1 0] P dimers on the surface. Each of the surfactants studied is found to result in disordering for layers grown using conditions that would otherwise produce highly ordered GaInP. Te yields disordered material with no change in the SPA spectra. However, the step velocity is found to increased markedly. Thus, the effect appears to be kinetic. Sb causes disordering due to a replacement of [ 1¯ 1 0] P dimers on the nominally (0 0 1) surface by larger Sb dimers, which reduces the strain-induced driving force for CuPt ordering at the surface. Thus, the effect is due to surface thermodynamics. For high Sb concentrations in the vapor, a triple-period ordered structure is formed. The appearance of this phase coincides with a distinct change in the surface reconstruction as indicated by SPA spectroscopy. Modulation of the TESb flow rate during growth was used to produce an abrupt order/disorder heterostructure with a bandgap energy difference of 135 meV with no significant change in solid composition at the interface. SPA results show that addition of As during growth also reduces the degree of order by displacing some of the [ 1¯ 1 0] P dimers on the surface. In this case, significant As concentrations in the solid of a few percent are observed. Thus, As is not an effective surfactant. Addition of Bi during growth results in a change in the surface reconstruction, as indicated by SPA spectroscopy, for Bi concentrations producing disordered GaInP. Unlike Sb and As, the Bi also causes a marked increase in the step velocity coincident with the loss of order. For singular (001) substrates, island formation is suppressed by Bi, resulting in the growth of much smoother layers. Modulation of the TMBi concentration during growth has been used to produce disorder/order heterostructures. The use of isoelectronic surfactants during growth to influence the properties of a semiconducting solid is a new and exciting development in control of the OMVPE growth process. It is expected that the use of isoelectronic surfactants to determine the surface reconstruction will find application in the growth of complex device structures. It also appears likely that this will be useful for controlling other characteristics of the growth process and the properties of the resultant semiconductor materials.

Surface passivation process of compound semiconductor material using UV photosulfidation

DOEpatents

Ashby, Carol I. H.

1995-01-01

A method for passivating compound semiconductor surfaces by photolytically disrupting molecular sulfur vapor with ultraviolet radiation to form reactive sulfur which then reacts with and passivates the surface of compound semiconductors.

Au-thiol interaction chemistry to influence the structural transformation of semiconductor nanocrystals and formation of giant nanostructures.

PubMed

Bose, Riya; Manna, Goutam; Pradhan, Narayan

2014-04-09

Giant nanostructures which are difficult to design by the classical growth process can be fabricated in a facilitated and well programmed surface ligand removal protocol employing the thiol-gold strong interaction chemistry. When thiol capped small ZnSe seed nanocrystals are treated with amine capped gold particles, gold snatches the thiol ligands from ZnSe and forces them to agglomerate leading to the giant crystalline ZnSe nanostructures. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Review on Organic-Inorganic Halide Perovskite Photodetectors: Device Engineering and Fundamental Physics.

PubMed

Ahmadi, Mahshid; Wu, Ting; Hu, Bin

2017-11-01

The last eight years (2009-2017) have seen an explosive growth of interest in organic-inorganic halide perovskites in the research communities of photovoltaics and light-emitting diodes. In addition, recent advancements have demonstrated that this type of perovskite has a great potential in the technology of light-signal detection with a comparable performance to commercially available crystalline Si and III-V photodetectors. The contemporary growth of state-of-the-art multifunctional perovskites in the field of light-signal detection has benefited from its outstanding intrinsic optoelectronic properties, including photoinduced polarization, high drift mobilities, and effective charge collection, which are excellent for this application. Photoactive perovskite semiconductors combine effective light absorption, allowing detection of a wide range of electromagnetic waves from ultraviolet and visible, to the near-infrared region, with low-cost solution processability and good photon yield. This class of semiconductor might empower breakthrough photodetector technology in the field of imaging, optical communications, and biomedical sensing. Therefore, here, the focus is specifically on the critical understanding of materials synthesis, design, and engineering for the next-stage development of perovskite photodetectors and highlighting the current challenges in the field, which need to be further studied in the future. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

EDITORIAL: Atomic layer deposition Atomic layer deposition

NASA Astrophysics Data System (ADS)

Godlewski, Marek

2012-07-01

The growth method of atomic layer deposition (ALD) was introduced in Finland by Suntola under the name of atomic layer epitaxy (ALE). The method was originally used for deposition of thin films of sulphides (ZnS, CaS, SrS) activated with manganese or rare-earth ions. Such films were grown for applications in thin-film electroluminescence (TFEL) displays. The ALE mode of growth was also tested in the case of molecular beam epitaxy. Films grown by ALD are commonly polycrystalline or even amorphous. Thus, the name ALE has been replaced by ALD. In the 80s ALD was developed mostly in Finland and neighboring Baltic countries. Deposition of a range of different materials was demonstrated at that time, including II-VI semiconductors (e.g. CdTe, CdS) and III-V (e.g. GaAs, GaN), with possible applications in e.g. photovoltaics. The number of publications on ALD was slowly increasing, approaching about 100 each year. A real boom in interest came with the development of deposition methods of thin films of high-k dielectrics. This research was motivated by a high leakage current in field-effect transistors with SiO2-based gate dielectrics. In 2007 Intel introduced a new generation of integrated circuits (ICs) with thin films of HfO2 used as gate isolating layers. In these and subsequent ICs, films of HfO2 are deposited by the ALD method. This is due to their unique properties. The introduction of ALD to the electronics industry led to a booming interest in the ALD growth method, with the number of publications increasing rapidly to well above 1000 each year. A number of new applications were proposed, as reflected in this special issue of Semiconductor Science and Technology. The included articles cover a wide range of possible applications—in microelectronics, transparent electronics, optoelectronics, photovoltaics and spintronics. Research papers and reviews on the basics of ALD growth are also included, reflecting a growing interest in precursor chemistry and growth processes. Summarizing, this special issue of Semiconductor Science and Technology reflects the rapidly growing interest in the ALD growth method and demonstrates the wide range of possible practical applications of ALD-grown materials, not only of high-k dielectrics, but also of a range of different materials (e.g. ZnO). Finally, I would like to thank the IOP editorial staff, in particular Alice Malhador, for their support and efforts in making this special issue possible.

Application of X-ray topography to USSR and Russian space materials science

PubMed Central

Shul’pina, I. L.; Prokhorov, I. A.; Serebryakov, Yu. A.; Bezbakh, I. Zh.

2016-01-01

The authors’ experience of the application of X-ray diffraction imaging in carrying out space technological experiments on semiconductor crystal growth for the former USSR and for Russia is reported, from the Apollo–Soyuz programme (1975) up to the present day. X-ray topography was applied to examine defects in crystals in order to obtain information on the crystallization conditions and also on their changes under the influence of factors of orbital flight in space vehicles. The data obtained have promoted a deeper understanding of the conditions and mechanisms of crystallization under both microgravity and terrestrial conditions, and have enabled the elaboration of terrestrial methods of highly perfect crystal growth. The use of X-ray topography in space materials science has enriched its methods in the field of digital image processing of growth striations and expanded its possibilities in investigating the inhomogeneity of crystals. PMID:27158506

Application of X-ray topography to USSR and Russian space materials science.

PubMed

Shul'pina, I L; Prokhorov, I A; Serebryakov, Yu A; Bezbakh, I Zh

2016-05-01

The authors' experience of the application of X-ray diffraction imaging in carrying out space technological experiments on semiconductor crystal growth for the former USSR and for Russia is reported, from the Apollo-Soyuz programme (1975) up to the present day. X-ray topography was applied to examine defects in crystals in order to obtain information on the crystallization conditions and also on their changes under the influence of factors of orbital flight in space vehicles. The data obtained have promoted a deeper understanding of the conditions and mechanisms of crystallization under both microgravity and terrestrial conditions, and have enabled the elaboration of terrestrial methods of highly perfect crystal growth. The use of X-ray topography in space materials science has enriched its methods in the field of digital image processing of growth striations and expanded its possibilities in investigating the inhomogeneity of crystals.

Site-Controlled Growth of Monolithic InGaAs/InP Quantum Well Nanopillar Lasers on Silicon.

PubMed

Schuster, Fabian; Kapraun, Jonas; Malheiros-Silveira, Gilliard N; Deshpande, Saniya; Chang-Hasnain, Connie J

2017-04-12

In this Letter, we report the site-controlled growth of InP nanolasers on a silicon substrate with patterned SiO 2 nanomasks by low-temperature metal-organic chemical vapor deposition, compatible with silicon complementary metal-oxide-semiconductor (CMOS) post-processing. A two-step growth procedure is presented to achieve smooth wurtzite faceting of vertical nanopillars. By incorporating InGaAs multiquantum wells, the nanopillar emission can be tuned over a wide spectral range. Enhanced quality factors of the intrinsic InP nanopillar cavities promote lasing at 0.87 and 1.21 μm, located within two important optical telecommunication bands. This is the first demonstration of a site-controlled III-V nanolaser monolithically integrated on silicon with a silicon-transparent emission wavelength, paving the way for energy-efficient on-chip optical links at typical telecommunication wavelengths.

Growth and characterization of vertical cavity structures on InP with GaAsSb/AlAsSb Bragg mirrors for 1.55 μm emission

NASA Astrophysics Data System (ADS)

Genty, Frédéric; Almuneau, Guilhem; Chusseau, Laurent; Wilk, Arnaud; Gaillard, Serge; Boissier, Guilhem; Grech, Pierre; Jacquet, Joel

1999-05-01

With the aim of fabricating vertical cavity semiconductor lasers (VCSEL), the molecular beam epitaxy growth of GaAsSb using two different element-V precursor sets has been first evaluated. Alloy compositions as well as ease of achieving lattice-matching are compared with both (As 2-Sb 4) or (As 2-Sb 2). Change in the growth mode process that depends on the precursor couple is presumed to influence strongly As and Sb incorporation rates thereby causing difficulties in reaching lattice-matching with Sb 4. The above study has allowed the fabrication of a fully doped 3 λ/2 monolithic Sb-based VCSEL on InP. The main devices performing at 77 K are a 200 nm wide stopband centered at 1.5 μm and a clear cavity resonance at 1.53 μm from which electroluminescence has been observed.

Photo-Spectrometer Realized In A Standard Cmos Ic Process

DOEpatents

Simpson, Michael L.; Ericson, M. Nance; Dress, William B.; Jellison, Gerald E.; Sitter, Jr., David N.; Wintenberg, Alan L.

1999-10-12

A spectrometer, comprises: a semiconductor having a silicon substrate, the substrate having integrally formed thereon a plurality of layers forming photo diodes, each of the photo diodes having an independent spectral response to an input spectra within a spectral range of the semiconductor and each of the photo diodes formed only from at least one of the plurality of layers of the semiconductor above the substrate; and, a signal processing circuit for modifying signals from the photo diodes with respective weights, the weighted signals being representative of a specific spectral response. The photo diodes have different junction depths and different polycrystalline silicon and oxide coverings. The signal processing circuit applies the respective weights and sums the weighted signals. In a corresponding method, a spectrometer is manufactured by manipulating only the standard masks, materials and fabrication steps of standard semiconductor processing, and integrating the spectrometer with a signal processing circuit.

Continuous replenishment of molten semiconductor in a Czochralski-process, single-crystal-growing furnace

NASA Technical Reports Server (NTRS)

Fiegl, George (Inventor); Torbet, Walter (Inventor)

1981-01-01

A replenishment crucible is mounted adjacent the usual drawing crucible, from which a monocrystalline boule is drawn according to the Czochralski method. A siphon tube for molten semiconductor transfer extends from the replenishment crucible to the drawing crucible. Each crucible is enclosed within its own hermetic shell and is provided with its own heater. The siphon tube is initially filled with molten semiconductor by raising the inert atmospheric pressure in the shell surrounding the replenishment crucible above that surrounding the drawing crucible. Thereafter, adjustment of the level of molten semiconductor in the drawing crucible may be achieved by adjusting the level in either crucible, since the siphon tube will establish the same level in both crucibles. For continuous processing, solid semiconductor may be added to and melted in the replenishment crucible during the process of drawing crystals from the drawing crucible. A constant liquid level of melted semiconductor is maintained in the system by an optical monitoring device and any of several electromechanical controls of the rate of replenishment or crucible height.

Bottom-Up Tri-gate Transistors and Submicrosecond Photodetectors from Guided CdS Nanowalls.

PubMed

Xu, Jinyou; Oksenberg, Eitan; Popovitz-Biro, Ronit; Rechav, Katya; Joselevich, Ernesto

2017-11-08

Tri-gate transistors offer better performance than planar transistors by exerting additional gate control over a channel from two lateral sides of semiconductor nanowalls (or "fins"). Here we report the bottom-up assembly of aligned CdS nanowalls by a simultaneous combination of horizontal catalytic vapor-liquid-solid growth and vertical facet-selective noncatalytic vapor-solid growth and their parallel integration into tri-gate transistors and photodetectors at wafer scale (cm 2 ) without postgrowth transfer or alignment steps. These tri-gate transistors act as enhancement-mode transistors with an on/off current ratio on the order of 10 8 , 4 orders of magnitude higher than the best results ever reported for planar enhancement-mode CdS transistors. The response time of the photodetector is reduced to the submicrosecond level, 1 order of magnitude shorter than the best results ever reported for photodetectors made of bottom-up semiconductor nanostructures. Guided semiconductor nanowalls open new opportunities for high-performance 3D nanodevices assembled from the bottom up.

Facile Five-Step Heteroepitaxial Growth of GaAs Nanowires on Silicon Substrates and the Twin Formation Mechanism.

PubMed

Yao, Maoqing; Sheng, Chunyang; Ge, Mingyuan; Chi, Chun-Yung; Cong, Sen; Nakano, Aiichiro; Dapkus, P Daniel; Zhou, Chongwu

2016-02-23

Monolithic integration of III-V semiconductors with Si has been pursued for some time in the semiconductor industry. However, the mismatch of lattice constants and thermal expansion coefficients represents a large technological challenge for the heteroepitaxial growth. Nanowires, due to their small lateral dimension, can relieve strain and mitigate dislocation formation to allow single-crystal III-V materials to be grown on Si. Here, we report a facile five-step heteroepitaxial growth of GaAs nanowires on Si using selective area growth (SAG) in metalorganic chemical vapor deposition, and we further report an in-depth study on the twin formation mechanism. Rotational twin defects were observed in the nanowire structures and showed strong dependence on the growth condition and nanowire size. We adopt a model of faceted growth to demonstrate the formation of twins during growth, which is well supported by both a transmission electron microscopy study and simulation based on nucleation energetics. Our study has led to twin-free segments in the length up to 80 nm, a significant improvement compared to previous work using SAG. The achievements may open up opportunities for future functional III-V-on-Si heterostructure devices.

Solid State Research, 1973:2.

DTIC Science & Technology

MERCURY COMPOUNDS, CADMIUM COMPOUNDS, TELLURIDES, NEODYMIUM COMPOUNDS, PHOSPHATES , ELECTRON TRANSITIONS, INFRARED OPTICAL MATERIALS, CRYSTAL GROWTH, MAGNESIUM OXIDES, PHOSPHORESCENT MATERIALS, SEMICONDUCTOR DIODES, MICROELECTRONICS

Sensors for process control Focus Team report

NASA Astrophysics Data System (ADS)

At the Semiconductor Technology Workshop, held in November 1992, the Semiconductor Industry Association (SIA) convened 179 semiconductor technology experts to assess the 15-year outlook for the semiconductor manufacturing industry. The output of the Workshop, a document entitled 'Semiconductor Technology: Workshop Working Group Reports,' contained an overall roadmap for the technology characteristics envisioned in integrated circuits (IC's) for the period 1992-2007. In addition, the document contained individual roadmaps for numerous key areas in IC manufacturing, such as film deposition, thermal processing, manufacturing systems, exposure technology, etc. The SIA Report did not contain a separate roadmap for contamination free manufacturing (CFM). A key component of CFM for the next 15 years is the use of sensors for (1) defect reduction, (2) improved product quality, (3) improved yield, (4) improved tool utilization through contamination reduction, and (5) real time process control in semiconductor fabrication. The objective of this Focus Team is to generate a Sensors for Process Control Roadmap. Implicit in this objective is the identification of gaps in current sensor technology so that research and development activity in the sensor industry can be stimulated to develop sensor systems capable of meeting the projected roadmap needs. Sensor performance features of interest include detection limit, specificity, sensitivity, ease of installation and maintenance, range, response time, accuracy, precision, ease and frequency of calibration, degree of automation, and adaptability to in-line process control applications.

Three-dimensional GaN/AlN nanowire heterostructures by separating nucleation and growth processes.

PubMed

Carnevale, Santino D; Yang, Jing; Phillips, Patrick J; Mills, Michael J; Myers, Roberto C

2011-02-09

Bottom-up nanostructure assembly has been a central theme of materials synthesis over the past few decades. Semiconductor quantum dots and nanowires provide additional degrees of freedom for charge confinement, strain engineering, and surface sensitivity-properties that are useful to a wide range of solid state optical and electronic technologies. A central challenge is to understand and manipulate nanostructure assembly to reproducibly generate emergent structures with the desired properties. However, progress is hampered due to the interdependence of nucleation and growth phenomena. Here we show that by dynamically adjusting the growth kinetics, it is possible to separate the nucleation and growth processes in spontaneously formed GaN nanowires using a two-step molecular beam epitaxy technique. First, a growth phase diagram for these nanowires is systematically developed, which allows for control of nanowire density over three orders of magnitude. Next, we show that by first nucleating nanowires at a low temperature and then growing them at a higher temperature, height and density can be independently selected while maintaining the target density over long growth times. GaN nanowires prepared using this two-step procedure are overgrown with three-dimensionally layered and topologically complex heterostructures of (GaN/AlN). By adjusting the growth temperature in the second growth step either vertical or coaxial nanowire superlattices can be formed. These results indicate that a two-step method allows access to a variety of kinetics at which nanowire nucleation and adatom mobility are adjustable.

A compact semiconductor digital interferometer and its applications

NASA Astrophysics Data System (ADS)

Britsky, Oleksander I.; Gorbov, Ivan V.; Petrov, Viacheslav V.; Balagura, Iryna V.

2015-05-01

The possibility of using semiconductor laser interferometers to measure displacements at the nanometer scale was demonstrated. The creation principles of miniature digital Michelson interferometers based on semiconductor lasers were proposed. The advanced processing algorithm for the interferometer quadrature signals was designed. It enabled to reduce restrictions on speed of measured movements. A miniature semiconductor digital Michelson interferometer was developed. Designing of the precision temperature stability system for miniature low-cost semiconductor laser with 0.01ºС accuracy enabled to use it for creation of compact interferometer rather than a helium-neon one. Proper firmware and software was designed for the interferometer signals real-time processing and conversion in to respective shifts. In the result the relative displacement between 0-500 mm was measured with a resolution of better than 1 nm. Advantages and disadvantages of practical use of the compact semiconductor digital interferometer in seismometers for the measurement of shifts were shown.

Numerical grid generation in computational field simulations. Volume 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soni, B.K.; Thompson, J.F.; Haeuser, J.

1996-12-31

To enhance the CFS technology to its next level of applicability (i.e., to create acceptance of CFS in an integrated product and process development involving multidisciplinary optimization) the basic requirements are: rapid turn-around time, reliable and accurate simulation, affordability and appropriate linkage to other engineering disciplines. In response to this demand, there has been a considerable growth in the grid generation related research activities involving automization, parallel processing, linkage with the CAD-CAM systems, CFS with dynamic motion and moving boundaries, strategies and algorithms associated with multi-block structured, unstructured, hybrid, hexahedral, and Cartesian grids, along with its applicability to various disciplinesmore » including biomedical, semiconductor, geophysical, ocean modeling, and multidisciplinary optimization.« less

Technicians monitor USMP-4 experiments being prepared for flight on STS-87 in the SSPF

NASA Technical Reports Server (NTRS)

1997-01-01

Technicians are monitoring experiments on the United States Microgravity Payload-4 (USMP-4) in preparation for its scheduled launch aboard STS-87 on Nov. 19 from Kennedy Space Center (KSC). USMP-4 experiments are prepared in the Space Station Processing Facility at KSC. The large white vertical cylinder in the center of the photo is the Advanced Automated Directional Solidification Furnace (AADSF), which is a sophisticated materials science facility used for studying a common method of processing semiconductor crystals called directional solidification. The white horizontal tube to the right is the Isothermal Dendritic Growth Experiment (IDGE), which will be used to study the dendritic solidification of molten materials in the microgravity environment.

Technicians monitor USMP-4 experiments being prepared for flight on STS-87 in the SSPF

NASA Technical Reports Server (NTRS)

1997-01-01

Technicians are monitoring experiments on the United States Microgravity Payload-4 (USMP-4) in preparation for its scheduled launch aboard STS-87 on Nov. 19 from Kennedy Space Center (KSC). USMP-4 experiments are prepared in the Space Station Processing Facility at KSC. The large white vertical cylinder at the right of the photo is the Advanced Automated Directional Solidification Furnace (AADSF ), which is a sophisticated materials science facility used for studying a common method of processing semiconductor crystals called directional solidification. The technician in the middle of the photo is leaning over MEPHISTO, a cooperative American-French investigation of the fundamentals of crystal growth.

Solid-state-based analog of optomechanics

DOE PAGES

Naumann, Nicolas L.; Droenner, Leon; Carmele, Alexander; ...

2016-09-01

In this study, we investigate a semiconductor quantum dot as a microscopic analog of a basic optomechanical setup. We show that optomechanical features can be reproduced by the solid-state platform, arising from parallels of the underlying interaction processes, which in the optomechanical case is the radiation pressure coupling and in the semiconductor case the electron–phonon coupling. We discuss bistabilities, lasing, and phonon damping, and recover the same qualitative behaviors for the semiconductor and the optomechanical cases expected for low driving strengths. However, in contrast to the optomechanical case, distinct signatures of higher order processes arise in the semiconductor model.

Ripening of Semiconductor Nanoplatelets.

PubMed

Ott, Florian D; Riedinger, Andreas; Ochsenbein, David R; Knüsel, Philippe N; Erwin, Steven C; Mazzotti, Marco; Norris, David J

2017-11-08

Ostwald ripening describes how the size distribution of colloidal particles evolves with time due to thermodynamic driving forces. Typically, small particles shrink and provide material to larger particles, which leads to size defocusing. Semiconductor nanoplatelets, thin quasi-two-dimensional (2D) particles with thicknesses of only a few atomic layers but larger lateral dimensions, offer a unique system to investigate this phenomenon. Experiments show that the distribution of nanoplatelet thicknesses does not defocus during ripening, but instead jumps sequentially from m to (m + 1) monolayers, allowing precise thickness control. We investigate how this counterintuitive process occurs in CdSe nanoplatelets. We develop a microscopic model that treats the kinetics and thermodynamics of attachment and detachment of monomers as a function of their concentration. We then simulate the growth process from nucleation through ripening. For a given thickness, we observe Ostwald ripening in the lateral direction, but none perpendicular. Thicker populations arise instead from nuclei that capture material from thinner nanoplatelets as they dissolve laterally. Optical experiments that attempt to track the thickness and lateral extent of nanoplatelets during ripening appear consistent with these conclusions. Understanding such effects can lead to better synthetic control, enabling further exploration of quasi-2D nanomaterials.

Scalable Directed Assembly of Highly Crystalline 2,7-Dioctyl[1]benzothieno[3,2- b][1]benzothiophene (C8-BTBT) Films.

PubMed

Chai, Zhimin; Abbasi, Salman A; Busnaina, Ahmed A

2018-05-30

Assembly of organic semiconductors with ordered crystal structure has been actively pursued for electronics applications such as organic field-effect transistors (OFETs). Among various film deposition methods, solution-based film growth from small molecule semiconductors is preferable because of its low material and energy consumption, low cost, and scalability. Here, we show scalable and controllable directed assembly of highly crystalline 2,7-dioctyl[1]benzothieno[3,2- b][1]benzothiophene (C8-BTBT) films via a dip-coating process. Self-aligned stripe patterns with tunable thickness and morphology over a centimeter scale are obtained by adjusting two governing parameters: the pulling speed of a substrate and the solution concentration. OFETs are fabricated using the C8-BTBT films assembled at various conditions. A field-effect hole mobility up to 3.99 cm 2 V -1 s -1 is obtained. Owing to the highly scalable crystalline film formation, the dip-coating directed assembly process could be a great candidate for manufacturing next-generation electronics. Meanwhile, the film formation mechanism discussed in this paper could provide a general guideline to prepare other organic semiconducting films from small molecule solutions.

Hierarchical structures of carbon nanotubes and arrays of chromium-capped silicon nanopillars: formation and electrical properties.

PubMed

Koch, Stefan; Joshi, Ravi K; Noyong, Michael; Timper, Jan; Schneider, Jörg J; Simon, Ulrich

2012-09-10

The formation of stochastically oriented carbon-nanotube networks on top of an array of free-standing chromium-capped silicon nanopillars is reported. The combination of nanosphere lithography and chemical vapor deposition enables the construction of nanostructures that exhibit a hierarchical sequence of structural sizes. Metallic chromium serves as an etching mask for Si-pillar formation and as a nucleation site for the formation of carbon nanotubes through the chemical vapor deposition of ethene, ethanol, and methane, respectively, thereby bridging individual pillars from top to top. Iron and cobalt were applied onto the chromium caps as catalysts for CNT growth and the influence of different carbon sources and different gas-flow rates were investigated. The carbon nanotubes were structurally characterized and their DC electrical properties were studied by in situ local- and ex situ macroscopic measurements, both of which reveal their semiconductor properties. This process demonstrates how carbon nanotubes can be integrated into Si-based semiconductors and, thus, this process may be used to form high-surface-area sensors or new porous catalyst supports with enhanced gas-permeation properties. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Growth of Compound Semiconductors in a Low Gravity Environment: Microgravity Growth of PbSnTe

NASA Technical Reports Server (NTRS)

Fripp, A. L.; Debnam, W. J.; Rosch, W. R.; Baker, N. R.; Narayanan, R.

1999-01-01

The growth of the alloy compound semiconductor lead tin telluride (PbSnTe) was chosen for a microgravity flight experiment in the Advanced Automated Directional Solidification Furnace (AADSF), on the United States Microgravity Payload-3 (USNP-3) in February, 1996 and on USNW- 4 in November, 1997. The objective of these experiments was to determine the effect of the reduction in convection, during the growth process, brought about by the microgravity environment. The properties of devices made from PbSnTe, an alloy of PbTe and SnTe, are dependent on the ratio of the elemental components in the starting crystal. Compositional uniformity in the crystal is only obtained if there is no significant mixing in the liquid during growth. The technological importance of PbSnTe lies in its band gap versus composition diagram which has a zero energy crossing at approximately 40% SnTe. This facilitates the construction of long wavelength (greater than 6 gm) infrared detectors and lasers. The properties and utilization of PbSnTe are the subject of other papers. 1,2 PbSnTe is also interesting from a purely scientific point of view. It is, potentially, both solutally and thermally unstable due to the temperature and density gradients present during growth. Density gradients, through thermal expansion, are imposed in directional solidification because temperature gradients are required to extract heat. Solutal gradients occur in directional solidification of alloys due to segregation at the interface. Usually the gradients vary with both experiment design and inherent materials properties. In a simplified one dimensional analysis with the growth axis parallel to the gravity vector, only one of the two instabilities work at a time. During growth, the temperature in the liquid increases ahead of the interface. Therefore the density, due to thermal expansion, is decreasing in that direction. However, the phase diagram shows that the lighter SnTe is preferentially rejected at the interface. This causes the liquid density to increase with distance away from the interface.

GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies.

PubMed

Yoon, Jongseung; Jo, Sungjin; Chun, Ik Su; Jung, Inhwa; Kim, Hoon-Sik; Meitl, Matthew; Menard, Etienne; Li, Xiuling; Coleman, James J; Paik, Ungyu; Rogers, John A

2010-05-20

Compound semiconductors like gallium arsenide (GaAs) provide advantages over silicon for many applications, owing to their direct bandgaps and high electron mobilities. Examples range from efficient photovoltaic devices to radio-frequency electronics and most forms of optoelectronics. However, growing large, high quality wafers of these materials, and intimately integrating them on silicon or amorphous substrates (such as glass or plastic) is expensive, which restricts their use. Here we describe materials and fabrication concepts that address many of these challenges, through the use of films of GaAs or AlGaAs grown in thick, multilayer epitaxial assemblies, then separated from each other and distributed on foreign substrates by printing. This method yields large quantities of high quality semiconductor material capable of device integration in large area formats, in a manner that also allows the wafer to be reused for additional growths. We demonstrate some capabilities of this approach with three different applications: GaAs-based metal semiconductor field effect transistors and logic gates on plates of glass, near-infrared imaging devices on wafers of silicon, and photovoltaic modules on sheets of plastic. These results illustrate the implementation of compound semiconductors such as GaAs in applications whose cost structures, formats, area coverages or modes of use are incompatible with conventional growth or integration strategies.

Atomic Scale Dynamics of Contact Formation in the Cross-Section of InGaAs Nanowire Channels

DOE PAGES

Chen, Renjie; Jungjohann, Katherine L.; Mook, William M.; ...

2017-03-23

In the alloyed and compound contacts between metal and semiconductor transistor channels we see that they enable self-aligned gate processes which play a significant role in transistor scaling. At nanoscale dimensions and for nanowire channels, prior experiments focused on reactions along the channel length, but the early stage of reaction in their cross sections remains unknown. We report on the dynamics of the solid-state reaction between metal (Ni) and semiconductor (In 0.53Ga 0.47As), along the cross-section of nanowires that are 15 nm in width. Unlike planar structures where crystalline nickelide readily forms at conventional, low alloying temperatures, nanowires exhibit amore » solid-state amorphization step that can undergo a crystal regrowth step at elevated temperatures. Here, we capture the layer-by-layer reaction mechanism and growth rate anisotropy using in situ transmission electron microscopy (TEM). Our kinetic model depicts this new, in-plane contact formation which could pave the way for engineered nanoscale transistors.« less

The Power of Materials Science Tools for Gaining Insights into Organic Semiconductors

NASA Astrophysics Data System (ADS)

Treat, Neil D.; Westacott, Paul; Stingelin, Natalie

2015-07-01

The structure of organic semiconductors can be complex because features from the molecular level (such as molecular conformation) to the micrometer scale (such as the volume fraction and composition of phases, phase distribution, and domain size) contribute to the definition of the optoelectronic landscape of the final architectures and, hence, to device performance. As a consequence, a detailed understanding of how to manipulate molecular ordering, e.g., through knowledge of relevant phase transitions, of the solidification process, of relevant solidification mechanisms, and of kinetic factors, is required to induce the desired optoelectronic response. In this review, we discuss relevant structural features of single-component and multicomponent systems; provide a case study of the multifaceted structure that polymer:fullerene systems can adopt; and highlight relevant solidification mechanisms such as nucleation and growth, liquid-liquid phase separation, and spinodal decomposition. In addition, cocrystal formation, solid solutions, and eutectic systems are treated and their relevance within the optoelectronic area emphasized.

High-temperature electronics

NASA Technical Reports Server (NTRS)

Seng, Gary T.

1987-01-01

In recent years, there was a growing need for electronics capable of sustained high-temperature operation for aerospace propulsion system instrumentation, control and condition monitoring, and integrated sensors. The desired operating temperature in some applications exceeds 600 C, which is well beyond the capability of currently available semiconductor devices. Silicon carbide displays a number of properties which make it very attractive as a semiconductor material, one of which is the ability to retain its electronic integrity at temperatures well above 600 C. An IR-100 award was presented to NASA Lewis in 1983 for developing a chemical vapor deposition process to grow single crystals of this material on standard silicon wafers. Silicon carbide devices were demonstrated above 400 C, but much work remains in the areas of crystal growth, characterization, and device fabrication before the full potential of silicon carbide can be realized. The presentation will conclude with current and future high-temperature electronics program plans. Although the development of silicon carbide falls into the category of high-risk research, the future looks promising, and the potential payoffs are tremendous.

Semiconductor Nanomembrane Tubes: Three-Dimensional Confinement for Controlled Neurite Outgrowth

PubMed Central

Yu, Minrui; Huang, Yu; Ballweg, Jason; Shin, Hyuncheol; Huang, Minghuang; Savage, Donald E.; Lagally, Max G.; Dent, Erik W.; Blick, Robert H.; Williams, Justin C.

2013-01-01

In many neural culture studies, neurite migration on a flat, open surface does not reflect the three-dimensional (3D) microenvironment in vivo. With that in mind, we fabricated arrays of semiconductor tubes using strained silicon (Si) and germanium (Ge) nanomembranes and employed them as a cell culture substrate for primary cortical neurons. Our experiments show that the SiGe substrate and the tube fabrication process are biologically viable for neuron cells. We also observe that neurons are attracted by the tube topography, even in the absence of adhesion factors, and can be guided to pass through the tubes during outgrowth. Coupled with selective seeding of individual neurons close to the tube opening, growth within a tube can be limited to a single axon. Furthermore, the tube feature resembles the natural myelin, both physically and electrically, and it is possible to control the tube diameter to be close to that of an axon, providing a confined 3D contact with the axon membrane and potentially insulating it from the extracellular solution. PMID:21366271

Electroless silver plating of the surface of organic semiconductors.

PubMed

Campione, Marcello; Parravicini, Matteo; Moret, Massimo; Papagni, Antonio; Schröter, Bernd; Fritz, Torsten

2011-10-04

The integration of nanoscale processes and devices demands fabrication routes involving rapid, cost-effective steps, preferably carried out under ambient conditions. The realization of the metal/organic semiconductor interface is one of the most demanding steps of device fabrication, since it requires mechanical and/or thermal treatments which increment costs and are often harmful in respect to the active layer. Here, we provide a microscopic analysis of a room temperature, electroless process aimed at the deposition of a nanostructured metallic silver layer with controlled coverage atop the surface of single crystals and thin films of organic semiconductors. This process relies on the reaction of aqueous AgF solutions with the nonwettable crystalline surface of donor-type organic semiconductors. It is observed that the formation of a uniform layer of silver nanoparticles can be accomplished within 20 min contact time. The electrical characterization of two-terminal devices performed before and after the aforementioned treatment shows that the metal deposition process is associated with a redox reaction causing the p-doping of the semiconductor. © 2011 American Chemical Society

Multifunctional Organic-Semiconductor Interfacial Layers for Solution-Processed Oxide-Semiconductor Thin-Film Transistor.

PubMed

Kwon, Guhyun; Kim, Keetae; Choi, Byung Doo; Roh, Jeongkyun; Lee, Changhee; Noh, Yong-Young; Seo, SungYong; Kim, Myung-Gil; Kim, Choongik

2017-06-01

The stabilization and control of the electrical properties in solution-processed amorphous-oxide semiconductors (AOSs) is crucial for the realization of cost-effective, high-performance, large-area electronics. In particular, impurity diffusion, electrical instability, and the lack of a general substitutional doping strategy for the active layer hinder the industrial implementation of copper electrodes and the fine tuning of the electrical parameters of AOS-based thin-film transistors (TFTs). In this study, the authors employ a multifunctional organic-semiconductor (OSC) interlayer as a solution-processed thin-film passivation layer and a charge-transfer dopant. As an electrically active impurity blocking layer, the OSC interlayer enhances the electrical stability of AOS TFTs by suppressing the adsorption of environmental gas species and copper-ion diffusion. Moreover, charge transfer between the organic interlayer and the AOS allows the fine tuning of the electrical properties and the passivation of the electrical defects in the AOS TFTs. The development of a multifunctional solution-processed organic interlayer enables the production of low-cost, high-performance oxide semiconductor-based circuits. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal growth of compound semiconductors in a low-gravity environment (InGaAs crystals) (M-22)

NASA Technical Reports Server (NTRS)

Tatsumi, Masami

1993-01-01

Compound semiconductor crystals, such as gallium arsenide and indium phosphide crystals, have many interesting properties that silicon crystals lack, and they are expected to be used as materials for optic and/or electro-optic integrated devices. Generally speaking, alloy semiconductors, which consist of more than three elements, demonstrate new functions. For example, values of important parameters, such as lattice constant and emission wavelength, can be chosen independently. However, as it is easy for macroscopic and/or microscopic fluctuations of composition to occur in alloy semiconductor crystals, it is difficult to obtain crystals having homogeneous properties. Macroscopic change of composition in a crystal is caused by the segregation phenomenon. This phenomenon is due to a continuous change in the concentration of constituent elements at the solid-liquid interfacing during solidification. On Earth, attempts were made to obtain a crystal with homogeneous composition by maintaining a constant melt composition near the solid-liquid interface, through suppression of the convection flow of the melt by applying a magnetic field. However, the attempt was not completely successful. Convective flow does not occur in microgravity because the gravity in space is from four to six orders of magnitude less than that on Earth. In such a case, mass transfer in the melt is dominated by the diffusion phenomenon. So, if crystal growth is carried out at a rate that is higher than the rate of mass transfer due to this phenomenon, it is expected that crystals having a homogeneous composition will be obtained. In addition, it is also possible that microscopic composition fluctuations (striation) may disappear because microscopic fluctuations diminish in the absence of convection. We are going to grow a bulk-indium gallium arsenide (InGaAs) crystal using the gradient heating furnace (GHF) in the first material processing test (FMPT). The structure of the sample is shown where InGaAs polycrystals in a crucible are doubly sealed in two quartz tubes for safety. The GHF consists of two zones, namely, high temperature and low temperature zones, which results in a large temperature gradient at the interface. Crystal growth is performed by moving the furnace (i.e. the temperature profile) from the left to right at a definite rate. Thus, we will grow crystals both on Earth and in space under the same conditions. As previously described, it is possible to obtain good quality crystals which are homogeneous in composition both macroscopically and microscopically due to the lack of convection in space. We are planning to study the effects of convection on crystal growth from a melt by comparing and characterizing the properties of crystals grown on Earth with those grown in space.

Thermal analysis of the vertical bridgman semiconductor crystal growth technique. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Jasinski, T. J.

1982-01-01

The quality of semiconductor crystals grown by the vertical Bridgman technique is strongly influenced by the axial and radial variations of temperature within the charge. The relationship between the thermal parameters of the vertical Bridgman system and the thermal behavior of the charge are examined. Thermal models are developed which are capable of producing results expressable in analytical form and which can be used without recourse to extensive computer work for the preliminary thermal design of vertical Bridgman crystal growth systems. These models include the effects of thermal coupling between the furnace and the charge, charge translation rate, charge diameter, thickness and thermal conductivity of the confining crucible, thermal conductivity change and liberation of latent heat at the growth interface, and infinite charge length. The hot and cold zone regions, considered to be at spatially uniform temperatures, are separated by a gradient control region which provides added thermal design flexibility for controlling the temperature variations near the growth interface.

A numerical study of steady crystal growth in a vertical Bridgman device

NASA Astrophysics Data System (ADS)

Jalics, Miklos Kalman

Electronics based on semiconductors creates an enormous demand for high quality semiconductor single crystals. The vertical Bridgman device is commonly used for growing single crystals for a variety of materials such as GaAs, InP and HgCdTe. A mathematical model is presented for steady crystal growth under conditions where crystal growth is determined strictly by heat transfer. The ends of the ampoule are chosen far away from the insulation zone to allow for steady growth. A numerical solution is sought for this mathematical model. The equations are transformed into a rectangular geometry and appropriate finite difference techniques are applied on the transformed equations. Newton's method solves the nonlinear problem. To improve efficiency GMRES with preconditioning is used to compute the Newton iterates. The numerical results are used to compare with two current asymptotic theories that assume small Biot numbers. Results indicate that one of the asymptotic theories is accurate for even moderate Biot numbers.

Fabrication of Metallic Hollow Nanoparticles

NASA Technical Reports Server (NTRS)

Lillehei, Peter T. (Inventor); Chu, Sang-Hyon (Inventor); Park, Yeonjoon (Inventor); Kim, Jae-Woo (Inventor); Choi, Sr., Sang H. (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

2016-01-01

Metal and semiconductor nanoshells, particularly transition metal nanoshells, are fabricated using dendrimer molecules. Metallic colloids, metallic ions or semiconductors are attached to amine groups on the dendrimer surface in stabilized solution for the surface seeding method and the surface seedless method, respectively. Subsequently, the process is repeated with additional metallic ions or semiconductor, a stabilizer, and NaBH.sub.4 to increase the wall thickness of the metallic or semiconductor lining on the dendrimer surface. Metallic or semiconductor ions are automatically reduced on the metallic or semiconductor nanoparticles causing the formation of hollow metallic or semiconductor nanoparticles. The void size of the formed hollow nanoparticles depends on the dendrimer generation. The thickness of the metallic or semiconductor thin film around the dendrimer depends on the repetition times and the size of initial metallic or semiconductor seeds.

Ambipolar Small-Molecule:Polymer Blend Semiconductors for Solution-Processable Organic Field-Effect Transistors.

PubMed

Kang, Minji; Hwang, Hansu; Park, Won-Tae; Khim, Dongyoon; Yeo, Jun-Seok; Kim, Yunseul; Kim, Yeon-Ju; Noh, Yong-Young; Kim, Dong-Yu

2017-01-25

We report on the fabrication of an organic thin-film semiconductor formed using a blend solution of soluble ambipolar small molecules and an insulating polymer binder that exhibits vertical phase separation and uniform film formation. The semiconductor thin films are produced in a single step from a mixture containing a small molecular semiconductor, namely, quinoidal biselenophene (QBS), and a binder polymer, namely, poly(2-vinylnaphthalene) (PVN). Organic field-effect transistors (OFETs) based on QBS/PVN blend semiconductor are then assembled using top-gate/bottom-contact device configuration, which achieve almost four times higher mobility than the neat QBS semiconductor. Depth profile via secondary ion mass spectrometry and atomic force microscopy images indicate that the QBS domains in the films made from the blend are evenly distributed with a smooth morphology at the bottom of the PVN layer. Bias stress test and variable-temperature measurements on QBS-based OFETs reveal that the QBS/PVN blend semiconductor remarkably reduces the number of trap sites at the gate dielectric/semiconductor interface and the activation energy in the transistor channel. This work provides a one-step solution processing technique, which makes use of soluble ambipolar small molecules to form a thin-film semiconductor for application in high-performance OFETs.

Arbitrary cross-section SEM-cathodoluminescence imaging of growth sectors and local carrier concentrations within micro-sampled semiconductor nanorods

PubMed Central

Watanabe, Kentaro; Nagata, Takahiro; Oh, Seungjun; Wakayama, Yutaka; Sekiguchi, Takashi; Volk, János; Nakamura, Yoshiaki

2016-01-01

Future one-dimensional electronics require single-crystalline semiconductor free-standing nanorods grown with uniform electrical properties. However, this is currently unrealistic as each crystallographic plane of a nanorod grows at unique incorporation rates of environmental dopants, which forms axial and lateral growth sectors with different carrier concentrations. Here we propose a series of techniques that micro-sample a free-standing nanorod of interest, fabricate its arbitrary cross-sections by controlling focused ion beam incidence orientation, and visualize its internal carrier concentration map. ZnO nanorods are grown by selective area homoepitaxy in precursor aqueous solution, each of which has a (0001):+c top-plane and six {1–100}:m side-planes. Near-band-edge cathodoluminescence nanospectroscopy evaluates carrier concentration map within a nanorod at high spatial resolution (60 nm) and high sensitivity. It also visualizes +c and m growth sectors at arbitrary nanorod cross-section and history of local transient growth events within each growth sector. Our technique paves the way for well-defined bottom-up nanoelectronics. PMID:26881966

Origin of poor doping efficiency in solution processed organic semiconductors.

PubMed

Jha, Ajay; Duan, Hong-Guang; Tiwari, Vandana; Thorwart, Michael; Miller, R J Dwayne

2018-05-21

Doping is an extremely important process where intentional insertion of impurities in semiconductors controls their electronic properties. In organic semiconductors, one of the convenient, but inefficient, ways of doping is the spin casting of a precursor mixture of components in solution, followed by solvent evaporation. Active control over this process holds the key to significant improvements over current poor doping efficiencies. Yet, an optimized control can only come from a detailed understanding of electronic interactions responsible for the low doping efficiencies. Here, we use two-dimensional nonlinear optical spectroscopy to examine these interactions in the course of the doping process by probing the solution mixture of doped organic semiconductors. A dopant accepts an electron from the semiconductor and the two ions form a duplex of interacting charges known as ion-pair complexes. Well-resolved off-diagonal peaks in the two-dimensional spectra clearly demonstrate the electronic connectivity among the ions in solution. This electronic interaction represents a well resolved electrostatically bound state, as opposed to a random distribution of ions. We developed a theoretical model to recover the experimental data, which reveals an unexpectedly strong electronic coupling of ∼250 cm -1 with an intermolecular distance of ∼4.5 Å between ions in solution, which is approximately the expected distance in processed films. The fact that this relationship persists from solution to the processed film gives direct evidence that Coulomb interactions are retained from the precursor solution to the processed films. This memory effect renders the charge carriers equally bound also in the film and, hence, results in poor doping efficiencies. This new insight will help pave the way towards rational tailoring of the electronic interactions to improve doping efficiencies in processed organic semiconductor thin films.

Numerical Modeling of Crystal of ZnSe by Physical Vapor Transport - Towards a more Comprehensive Formulations

NASA Technical Reports Server (NTRS)

Ramachandran, N.

1999-01-01

Crystal growth from the vapor phase has various advantages over melt growth. The main advantage is from a lower processing temperature which makes the process more amenable in instances where the melting temperature of the crystal is high. Other benefits stem from the inherent purification mechanism in the process due to differences in the vapor pressures of the native elements and impurities, and the enhanced interfacial morphological stability during the growth process. Further, the implementation of PVT growth in closed ampoules affords experimental simplicity with minimal needs for complex process control which makes it an ideal candidate for space investigations in systems where gravity tends to have undesirable effects on the growth process. Bulk growth of wide band gap II-VI semiconductors by physical vapor transport has been developed and refined over the past several years at NASA MSFC. Results from a modeling study of PVT crystal growth of ZnSe are reported in this paper. The PVT process is numerically investigated using both two-dimensional and fully three-dimensional formulation of the governing equations and associated boundary conditions. Both the incompressible Boussinesq approximation and the compressible model are tested to determine the influence of gravity on the process and to discern the differences between the two approaches. The influence of a residual gas is included in the models. The results show that both the incompressible and compressible approximations provide comparable results and the presence of a residual gas tends to measurably reduce the mass flux in the system. Detailed flow, thermal and concentration profiles will be provided in the final manuscript along with computed heat and mass transfer rates. Comparisons with the 1-D model will also be provided. The effect of gravity on the process from numerical computations shows subtle effects although experimental evidence from vertically and horizontally grown samples show dramatic evidence of gravitational effects. The shortcomings of the problem formulation will be discussed and a framework will be provided leading up towards a more comprehensive model of PVT systems.

Process waste assessment: Petroleum jelly removal from semiconductor die using trichloroethylene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtin, D.P.

The process analyzed involves non-production, laboratory environment use of trichloroethylene for the cleaning of semiconductor devices. The option selection centered on the replacement of the trichloroethylene with a non-hazardous material. This process waste assessment was performed as part of a pilot project.

New materials and structures for photovoltaics

NASA Astrophysics Data System (ADS)

Zunger, Alex; Wagner, S.; Petroff, P. M.

1993-01-01

Despite the fact that over the years crystal chemists have discovered numerous semiconducting substances, and that modern epitaxial growth techniques are able to produce many novel atomic-scale architectures, current electronic and opto-electronic technologies are based but on a handful of ˜10 traditional semiconductor core materials. This paper surveys a number of yet-unexploited classes of semiconductors, pointing to the much-needed research in screening, growing, and characterizing promising members of these classes. In light of the unmanageably large number of a-priori possibilities, we emphasize the role that structural chemistry and modern computer-aided design must play in screening potentially important candidates. The basic classes of materials discussed here include nontraditional alloys, such as non-isovalent and heterostructural semiconductors, materials at reduced dimensionality, including superlattices, zeolite-caged nanostructures and organic semiconductors, spontaneously ordered alloys, interstitial semiconductors, filled tetrahedral structures, ordered vacancy compounds, and compounds based on d and f electron elements. A collaborative effort among material predictor, material grower, and material characterizer holds the promise for a successful identification of new and exciting systems.

An Ultrathin Single Crystalline Relaxor Ferroelectric Integrated on a High Mobility Semiconductor.

PubMed

Moghadam, Reza M; Xiao, Zhiyong; Ahmadi-Majlan, Kamyar; Grimley, Everett D; Bowden, Mark; Ong, Phuong-Vu; Chambers, Scott A; Lebeau, James M; Hong, Xia; Sushko, Peter V; Ngai, Joseph H

2017-10-11

The epitaxial growth of multifunctional oxides on semiconductors has opened a pathway to introduce new functionalities to semiconductor device technologies. In particular, the integration of gate materials that enable nonvolatile or hysteretic functionality in field-effect transistors could lead to device technologies that consume less power or allow for novel modalities in computing. Here we present electrical characterization of ultrathin single crystalline SrZr x Ti 1-x O 3 (x = 0.7) films epitaxially grown on a high mobility semiconductor, Ge. Epitaxial films of SrZr x Ti 1-x O 3 exhibit relaxor behavior, characterized by a hysteretic polarization that can modulate the surface potential of Ge. We find that gate layers as thin as 5 nm corresponding to an equivalent-oxide thickness of just 1.0 nm exhibit a ∼2 V hysteretic window in the capacitance-voltage characteristics. The development of hysteretic metal-oxide-semiconductor capacitors with nanoscale gate thicknesses opens new vistas for nanoelectronic devices.

Integrated Multi-Color Light Emitting Device Made with Hybrid Crystal Structure

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor)

2017-01-01

An integrated hybrid crystal Light Emitting Diode ("LED") display device that may emit red, green, and blue colors on a single wafer. The various embodiments may provide double-sided hetero crystal growth with hexagonal wurtzite III-Nitride compound semiconductor on one side of (0001) c-plane sapphire media and cubic zinc-blended III-V or II-VI compound semiconductor on the opposite side of c-plane sapphire media. The c-plane sapphire media may be a bulk single crystalline c-plane sapphire wafer, a thin free standing c-plane sapphire layer, or crack-and-bonded c-plane sapphire layer on any substrate. The bandgap energies and lattice constants of the compound semiconductor alloys may be changed by mixing different amounts of ingredients of the same group into the compound semiconductor. The bandgap energy and lattice constant may be engineered by changing the alloy composition within the cubic group IV, group III-V, and group II-VI semiconductors and within the hexagonal III-Nitrides.

Integrated Multi-Color Light Emitting Device Made with Hybrid Crystal Structure

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor)

2016-01-01

An integrated hybrid crystal Light Emitting Diode ("LED") display device that may emit red, green, and blue colors on a single wafer. The various embodiments may provide double-sided hetero crystal growth with hexagonal wurtzite III-Nitride compound semiconductor on one side of (0001) c-plane sapphire media and cubic zinc-blended III-V or II-VI compound semiconductor on the opposite side of c-plane sapphire media. The c-plane sapphire media may be a bulk single crystalline c-plane sapphire wafer, a thin free standing c-plane sapphire layer, or crack-and-bonded c-plane sapphire layer on any substrate. The bandgap energies and lattice constants of the compound semiconductor alloys may be changed by mixing different amounts of ingredients of the same group into the compound semiconductor. The bandgap energy and lattice constant may be engineered by changing the alloy composition within the cubic group IV, group III-V, and group II-VI semiconductors and within the hexagonal III-Nitrides.

Dewetting During the Crystal Growth of (Cd,Zn)Te:In Under Microgravity

NASA Astrophysics Data System (ADS)

Sylla, Lamine; Fauler, Alex; Fiederle, Michael; Duffar, Thierry; Dieguez, Ernesto; Zanotti, Lucio; Zappettini, Andrea; Roosen, GÉrald

2009-08-01

The phenomenon of ldquodewettingrdquo associated with the Vertical Bridgman (VB) crystal growth technique leads to the growth of a crystal without contact with the crucible. One dramatic consequence of this modified VB process is the reduction of structural defects within the crystal. It has been observed in several microgravity experiments for different semiconductor crystals. This work is concentrated on the growth of high resistivity (Cd,Zn)Te:In (CZT) crystals by achieving the phenomenon of dewetting under microgravity condition and its application in the processing of CZT detectors. Two Cd0.9Zn0.1Te:In crystals were grown in space on the Russian FOTON satellite in the POLIZON-M facility in September 2007 (mission M3). At the end of the preliminary melting phase of one crystal, a Rotating Magnetic Field (RMF) was applied in order to reduce the typical tellurium clusters within the melt before the pulling. The other crystal was superheated with 20 K above the melting point before the pulling. A third reference crystal has been grown on the ground in similar thermal conditions. Profiles measurements of the space grown crystals surface gave the evidence of a successful dewetting during the crystal growth. Characterization methods such as IR microscopy and CoReMa have been performed on the three crystals. CZT detectors have been processed from the grown part of the different crystals. The influence of the dewetting on the material quality and the detector properties completes the study.

Investigating Morphological Stability of Faceted Interfaces with Axial Heat Processing (AHP) Technique

NASA Technical Reports Server (NTRS)

Abbaschian, Reza; Balikci, Ercan; Deal, Andrew; Gonik, Michael; Golyshev, Viladimir D.; Leonardi, Eddie; deVahlDavis, G.; Chen, P. Y. P.; Timchenko, V.

2003-01-01

Successful processing of homogeneous semiconductor single crystals from their melts depends strongly on precise control of thermal and fluid flow conditions near the solid/liquid interface. In this project, we utilize a novel crystal growth technique called Axial Heat Processing (AHP) that uses a baffle, positioned inside the melt near the interface, to supply and/or conduct heat axially to the interface. The baffle, which may or may not have a heater encased in it, can promote more stable and planar growth as well as reduce buoyancy driven convection. The latter is because the baffle reduces the aspect ratio of the melt as it separates the melt into three sections, above the baffle, in the feed gap between the baffle and the crucible wall, and below the baffle between the baffle base and the interface. AHP also enables a close monitoring and/or control of thermal boundaries near the solid/liquid interface during crystal growth by means of thermocouples placed in the baffle. The interface is kept planar when a heating element in the baffle is used. However, a proper choice of melt height is necessary to keep the interface planar when using the baffle without a heater. This study addresses the influence of melt height and growth velocity on the segregation profile of AHP-grown Sb doped Ge single crystals.

Reduction of Charge Traps and Stability Enhancement in Solution-Processed Organic Field-Effect Transistors Based on a Blended n-Type Semiconductor.

PubMed

Campos, Antonio; Riera-Galindo, Sergi; Puigdollers, Joaquim; Mas-Torrent, Marta

2018-05-09

Solution-processed n-type organic field-effect transistors (OFETs) are essential elements for developing large-area, low-cost, and all organic logic/complementary circuits. Nonetheless, the development of air-stable n-type organic semiconductors (OSCs) lags behind their p-type counterparts. The trapping of electrons at the semiconductor-dielectric interface leads to a lower performance and operational stability. Herein, we report printed small-molecule n-type OFETs based on a blend with a binder polymer, which enhances the device stability due to the improvement of the semiconductor-dielectric interface quality and a self-encapsulation. Both combined effects prevent the fast deterioration of the OSC. Additionally, a complementary metal-oxide semiconductor-like inverter is fabricated depositing p-type and n-type OSCs simultaneously.

Photo-thermal processing of semiconductor fibers and thin films

NASA Astrophysics Data System (ADS)

Gupta, Nishant

Furnace processing and rapid thermal processing (RTP) have been an integral part of several processing steps in semiconductor manufacturing. The performance of RTP techniques can be improved many times by exploiting quantum photo-effects of UV and vacuum ultraviolet (VUV) photons in thermal processing and this technique is known as rapid photo-thermal processing (RPP). As compared to furnace processing and RTP, RPP provides higher diffusion coefficient, lower stress and lower microscopic defects. In this work, a custom designed automated photo assisted processing system was built from individual parts and an incoherent light source. This photo-assisted processing system is used to anneal silica clad silicon fibers and deposit thin-films. To the best of our knowledge, incoherent light source based rapid photo-thermal processing (RPP) was used for the first time to anneal glass-clad silicon core optical fibers. X-ray diffraction examination, Raman spectroscopy and electrical measurements showed a considerable enhancement of structural and crystalline properties of RPP treated silicon fibers. Photons in UV and vacuum ultraviolet (VUV) regions play a very important role in improving the bulk and carrier transport properties of RPP-treated silicon optical fibers, and the resultant annealing permits a path forward to in situ enhancement of the structure and properties of these new crystalline core optical fibers. To explore further applications of RPP, thin-films of Calcium Copper Titanate (CaCu3Ti4O12) or CCTO and Copper (I) Oxide (Cu2O) were also deposited using photo-assisted metal-organic chemical vapor deposition (MOCVD) on Si/SiO2 and n-Si substrate respectively. CCTO is one of the most researched giant dielectric constant materials in recent years. The given photo-assisted MOCVD approach provided polycrystalline CCTO growth on a SiO2 surface with grain sizes as large as 410 nm. Copper (I) oxide (Cu2O) is a direct band gap semiconductor with p-type conductivity and is a potential candidate for multi-junction solar cells. X-ray diffraction study revealed a preferred orientation, as (200) oriented crystals of Cu2O are grown on both substrates. Also, electrical characterization of Cu2O/n-Si devices showed the lowest saturation current density of 1.5x10-12 A/cm 2 at zero bias. As a result, photo-assisted thermal processing has the potential of making the process more effective with enhanced device performance.

REDUCTION OF ARSENIC WASTES IN THE SEMICONDUCTOR INDUSTRY

EPA Science Inventory

The research described in this report was aimed at initiating and developing processes and process modifications that could be incorporated into semiconductor manufacturing operations to accomplish pollution prevention, especially to accomplish significant reduction in the quanti...

Thermoreflectance spectroscopy—Analysis of thermal processes in semiconductor lasers

NASA Astrophysics Data System (ADS)

Pierścińska, D.

2018-01-01

This review focuses on theoretical foundations, experimental implementation and an overview of experimental results of the thermoreflectance spectroscopy as a powerful technique for temperature monitoring and analysis of thermal processes in semiconductor lasers. This is an optical, non-contact, high spatial resolution technique providing high temperature resolution and mapping capabilities. Thermoreflectance is a thermometric technique based on measuring of relative change of reflectivity of the surface of laser facet, which provides thermal images useful in hot spot detection and reliability studies. In this paper, principles and experimental implementation of the technique as a thermography tool is discussed. Some exemplary applications of TR to various types of lasers are presented, proving that thermoreflectance technique provides new insight into heat management problems in semiconductor lasers and in particular, that it allows studying thermal degradation processes occurring at laser facets. Additionally, thermal processes and basic mechanisms of degradation of the semiconductor laser are discussed.

Effects of Excess Carriers on Charged Defect Concentrations in Wide Bandgap Semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alberi, Kirstin M; Scarpulla, Michael A.

Unintentional doping and doping limits in semiconductors are typically caused by compensating defects with low formation energies. Since the formation enthalpy of a charged defect depends linearly on the Fermi level, doping limits can be especially pronounced in wide bandgap semiconductors where the Fermi level can vary substantially. Introduction of non-equilibrium carrier concentrations during growth or processing alters the chemical potentials of band carriers and allows populations of charged defects to be modified in ways impossible at thermal equilibrium. We demonstrate that in the presence of excess carriers, the rates of carrier capture and emission involving a defect charge transitionmore » level determine the admixture of electron and hole quasi-Fermi levels involved in the formation enthalpy of non-zero charge defect states. To understand the range of possible responses, we investigate the behavior of a single donor-like defect as functions of extrinsic doping and charge transition level energy. We find that that excess carriers will increase the formation enthalpy of compensating defects for most values of the charge transition level in the bandgap. Thus, it may be possible to use non-equilibrium carrier concentrations to overcome limitations on doping imposed by native defects. Cases also exist in which the concentration of defects with the same charge polarity as the majority dopant is either left unchanged or actually increases. This surprising effect arises when emission rates are suppressed relative to the capture rates and is most pronounced in wide bandgap semiconductors. We provide guidelines for carrying out experimental tests of this model.« less

Effects of excess carriers on charged defect concentrations in wide bandgap semiconductors

NASA Astrophysics Data System (ADS)

Alberi, Kirstin; Scarpulla, Michael A.

2018-05-01

Unintentional doping and doping limits in semiconductors are typically caused by compensating defects with low formation energies. Since the formation enthalpy of a charged defect depends linearly on the Fermi level, doping limits can be especially pronounced in wide bandgap semiconductors where the Fermi level can vary substantially. Introduction of non-equilibrium carrier concentrations during growth or processing alters the chemical potentials of band carriers and allows populations of charged defects to be modified in ways impossible at thermal equilibrium. We demonstrate that in the presence of excess carriers, the rates of carrier capture and emission involving a defect charge transition level determine the admixture of electron and hole quasi-Fermi levels involved in the formation enthalpy of non-zero charge defect states. To understand the range of possible responses, we investigate the behavior of a single donor-like defect as functions of extrinsic doping and charge transition level energy. We find that that excess carriers will increase the formation enthalpy of compensating defects for most values of the charge transition level in the bandgap. Thus, it may be possible to use non-equilibrium carrier concentrations to overcome limitations on doping imposed by native defects. Cases also exist in which the concentration of defects with the same charge polarity as the majority dopant is either left unchanged or actually increases. This surprising effect arises when emission rates are suppressed relative to the capture rates and is most pronounced in wide bandgap semiconductors. We provide guidelines for carrying out experimental tests of this model.

Methods of Measurement for Semiconductor Materials, Process Control, and Devices

NASA Technical Reports Server (NTRS)

Bullis, W. M. (Editor)

1973-01-01

The development of methods of measurement for semiconductor materials, process control, and devices is reported. Significant accomplishments include: (1) Completion of an initial identification of the more important problems in process control for integrated circuit fabrication and assembly; (2) preparations for making silicon bulk resistivity wafer standards available to the industry; and (3) establishment of the relationship between carrier mobility and impurity density in silicon. Work is continuing on measurement of resistivity of semiconductor crystals; characterization of generation-recombination-trapping centers, including gold, in silicon; evaluation of wire bonds and die attachment; study of scanning electron microscopy for wafer inspection and test; measurement of thermal properties of semiconductor devices; determination of S-parameters and delay time in junction devices; and characterization of noise and conversion loss of microwave detector diodes.

Understanding the Vapor-Liquid-Solid and Vapor-Solid-Solid Mechanisms of Si Nanowire Growth to Synthetically Encode Precise Nanoscale Morphology

NASA Astrophysics Data System (ADS)

Pinion, Christopher William

Precise patterning of semiconductor materials utilizing top-down lithographic techniques is integral to the advanced electronics we use on a daily basis. However, continuing development of these lithographic technologies often results in the trade-off of either high cost or low throughput, and three-dimensional (3D) patterning can be difficult to achieve. Bottom-up, chemical methods to control the 3D nanoscale morphology of semiconductor nanostructures have received significant attention as a complementary technique. Semiconductor nanowires, nanoscale filaments of semiconductor material 10-500 nm in diameter and 1-50 microns in length, are an especially promising platform because the wire composition can be modulated during growth and the high aspect ratio, one-dimensional structure enables integration in a range of devices. In this thesis, we first report a bottom-up method to break the conventional "wire" symmetry and synthetically encode a high-resolution array of arbitrary shapes along the nanowire growth axis. Rapid modulation of phosphorus doping combined with selective wet-chemical etching enables morphological features as small as 10 nm to be patterned over wires more than 50 ?m in length. Next, our focus shifts to more fundamental studies of the nanowire synthetic mechanisms. We presented comprehensive experimental measurements on the growth rate of Au catalyzed Si nanowires and developed a kinetic model of vapor-liquid-solid growth. Our analysis revealed an abrupt transition from a diameter-independent growth rate that is limited by incorporation to a diameter-dependent growth rate that is limited by crystallization. While investigating the vapor-liquid-solid mechanism, we noticed instances of unique catalyst behavior. Upon further study, we showed that it is possible to instantaneously and reversibly switch the phase of the catalyst between a liquid and superheated solid state under isothermal conditions above the eutectic temperature. The solid catalyst induces a vapor-solid-solid growth mechanism, which provides atomic-level control of dopant atoms in the nanowire. Finally, we explored a promising application of nanowires by investigating the potential for complex silicon nanowires to serve as a platform for next-generation photovoltaic devices. We reviewed the synthesis, electrical, and optical characteristics of core/shell Si nanowires that are sub-wavelength in diameter and contain radial p-n junctions. We highlighted the unique features of these nanowires, such as optical antenna effects that concentrate light and intense built-in electric fields that enable ultrafast charge-carrier separation. Based on these observations we advocate for a paradigm in which nanowires are arranged in periodic horizontal arrays to form ultrathin devices.

Experimental methods of post-growth tuning of the excitonic fine structure splitting in semiconductor quantum dots

PubMed Central

2012-01-01

Deterministic sources of polarization entangled photon pairs on demand are considered as important building blocks for quantum communication technology. It has been demonstrated that semiconductor quantum dots (QDs), which exhibit a sufficiently small excitonic fine structure splitting (FSS) can be used as triggered, on-chip sources of polarization entangled photon pairs. As-grown QDs usually do not have the required values of the FSS, making the availability of post-growth tuning techniques highly desired. This article reviews the effect of different post-growth treatments and external fields on the FSS such as thermal annealing, magnetic fields, the optical Stark effect, electric fields, and anisotropic stress. As a consequence of the tuning of the FSS, for some tuning techniques a rotation of the polarization of the emitted light is observed. The joint modification of polarization orientation and FSS can be described by an anticrossing of the bright excitonic states. PMID:22726724

Low Temperature Photoluminescence Characterization of Orbitally Grown CdZnTe

NASA Technical Reports Server (NTRS)

Ritter, Timothy M.; Larson, D. J.

1998-01-01

The II-VI ternary alloy CdZnTe is a technologically important material because of its use as a lattice matched substrate for HgCdTe based devices. The increasingly stringent requirements on performance that must be met by such large area infrared detectors also necessitates a higher quality substrate. Such substrate material is typically grown using the Bridgman technique. Due to the nature of bulk semiconductor growth, gravitationally dependent phenomena can adversely affect crystalline quality. The most direct way to alleviate this problem is by crystal growth in a reduced gravity environment. Since it requires hours, even days, to grow a high quality crystal, an orbiting space shuttle or space station provides a superb platform on which to conduct such research. For well over ten years NASA has been studying the effects of microgravity semiconductor crystal growth. This paper reports the results of photoluminescence characterization performed on an arbitrary grown CdZnTe bulk crystal.

SEMICONDUCTOR TECHNOLOGY Supercritical carbon dioxide process for releasing stuck cantilever beams

NASA Astrophysics Data System (ADS)

Yu, Hui; Chaoqun, Gao; Lei, Wang; Yupeng, Jing

2010-10-01

The multi-SCCO2 (supercritical carbon dioxide) release and dry process based on our specialized SCCO2 semiconductor process equipment is investigated and the releasing mechanism is discussed. The experiment results show that stuck cantilever beams were held up again under SCCO2 high pressure treatment and the repeatability of this process is nearly 100%.

Surface diffusion effects on growth of nanowires by chemical beam epitaxy

NASA Astrophysics Data System (ADS)

Persson, A. I.; Fröberg, L. E.; Jeppesen, S.; Björk, M. T.; Samuelson, L.

2007-02-01

Surface processes play a large role in the growth of semiconductor nanowires by chemical beam epitaxy. In particular, for III-V nanowires the surface diffusion of group-III species is important to understand in order to control the nanowire growth. In this paper, we have grown InAs-based nanowires positioned by electron beam lithography and have investigated the dependence of the diffusion of In species on temperature, group-III and -V source pressure and group-V source combinations by measuring nanowire growth rate for different nanowire spacings. We present a model which relates the nanowire growth rate to the migration length of In species. The model is fitted to the experimental data for different growth conditions, using the migration length as fitting parameter. The results show that the migration length increases with decreasing temperature and increasing group-V/group-III source pressure ratio. This will most often lead to an increase in growth rate, but deviations will occur due to incomplete decomposition and changes in sticking coefficient for group-III species. The results also show that the introduction of phosphorous precursor for growth of InAs1-xPx nanowires decreases the migration length of the In species followed by a decrease in nanowire growth rate.

Plasma Processes for Semiconductor Fabrication

NASA Astrophysics Data System (ADS)

Hitchon, W. N. G.

1999-01-01

Plasma processing is a central technique in the fabrication of semiconductor devices. This self-contained book provides an up-to-date description of plasma etching and deposition in semiconductor fabrication. It presents the basic physics and chemistry of these processes, and shows how they can be accurately modeled. The author begins with an overview of plasma reactors and discusses the various models for understanding plasma processes. He then covers plasma chemistry, addressing the effects of different chemicals on the features being etched. Having presented the relevant background material, he then describes in detail the modeling of complex plasma systems, with reference to experimental results. The book closes with a useful glossary of technical terms. No prior knowledge of plasma physics is assumed in the book. It contains many homework exercises and serves as an ideal introduction to plasma processing and technology for graduate students of electrical engineering and materials science. It will also be a useful reference for practicing engineers in the semiconductor industry.

Chalcopyrite and Orientation-Patterned Semiconductors for Mid-IR Sources: Modeling, Growth, and Characterization

DTIC Science & Technology

2006-11-01

shallow 120-meV acceptor and residual donor impurities. To produce low -absorption material for use in nonlinear optical devices, it is necessary to reduce...our knowledge, -20x higher than in previously reported works. This is accomplished by simply inserting a layer of low - index material (AlxOy) in the...and thin - film ferromagnetic semiconductors with Curie points above room temperature, and characterization of their magnetic and transport properties

High Power Mid Wave Infrared Semiconductor Lasers

DTIC Science & Technology

2006-06-15

resonance and the gain spectrum. The devices were grown using solid source molecular beam epitaxy (MBE) in a V80 reactor. Two side polished, undoped...verify the inherent low activation energy. N-type and P-type AISb, and various compositions of InxAl 1xSb, were grown by solid-source molecular beam ...level monitoring. Advances in epitaxial growth of semiconductor materials have allowed the development of Arsenic- free optically-pumped MWIR lasers on

Processing of semiconductors and thin film solar cells using electroplating

NASA Astrophysics Data System (ADS)

Madugu, Mohammad Lamido

The global need for a clean, sustainable and affordable source of energy has triggered extensive research especially in renewable energy sources. In this sector, photovoltaic has been identified as a cheapest, clean and reliable source of energy. It would be of interest to obtain photovoltaic material in thin film form by using simple and inexpensive semiconductor growth technique such as electroplating. Using this growth technique, four semiconductor materials were electroplated on glass/fluorine-doped tin oxide (FTO) substrate from aqueous electrolytes. These semiconductors are indium selenide (In[x]Sey), zinc sulphide (ZnS), cadmium sulphide (CdS) and cadmium telluride (CdTe). In[x]Se[y] and ZnS were incorporated as buffer layers while CdS and CdTe layers were utilised as window and absorber layers respectively. All materials were grown using two-electrode (2E) system except for CdTe which was grown using 3E and 2E systems for comparison. To fully optimise the growth conditions, the as-deposited and annealed layers from all the materials were characterised for their structural, morphological, optical, electrical and defects structures using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), optical absorption (UV-Vis spectroscopy), photoelectrochemical (PEC) cell measurements, current-voltage (I-V), capacitance-voltage (C-V), DC electrical measurements, ultraviolet photoelectron spectroscopy (UPS) and photoluminescence (PL) techniques. Results show that InxSey and ZnS layers were amorphous in nature and exhibit both n-type and p-type in electrical conduction. CdS layers are n-type in electrical conduction and show hexagonal and cubic phases in both the as-deposited and after annealing process. CdTe layers show cubic phase structure with both n-type and p-type in electrical conduction. CdTe-based solar cell structures with a n-n heterojunction plus large Schottky barrier, as well as multi-layer graded bandgap solar cells were fabricated. This means that the solar cells investigated in this thesis were not the conventional p-n junction type solar cells. The conventional cadmium chloride (CdCl[2] or CC) treatment was applied to the structures to produce high performance devices; however, by modifying the treatment to include cadmium chloride and cadmium fluoride (CdCl[2]+CdF[2] or CF) device performance could be improved further. The fabricated devices were characterised using I-V and C-V measurement techniques. The highest cell efficiency achieved in this research was -10%, with an open circuit voltage of 640 mV, short-circuit current density of 38.1 mAcm[-2], fill factor of 0.41 and doping concentration of 2.07x1016 cm3. These parameters were obtained for the glass/FTO/n-In[x]Se[y]/n-CdS/n-CdTe/Au solar cell structure.

Solution-processed zinc oxide field-effect transistors based on self-assembly of colloidal nanorods.

PubMed

Sun, Baoquan; Sirringhaus, Henning

2005-12-01

Colloidal zinc oxide (ZnO) nanocrystals are attractive candidates for a low-temperature and solution-processible semiconductor for high-performance thin-film field-effect transistors (TFTs). Here we show that by controlling the shape of the nanocrystals from spheres to rods the semiconducting properties of spin-coated ZnO films can be much improved as a result of increasing particle size and self-alignment of the nanorods along the substrate. Postdeposition hydrothermal growth in an aqueous zinc ion solution has been found to further enhance grain size and connectivity and improve device performance. TFT devices made from 65-nm-long and 10-nm-wide nanorods deposited by spin coating have been fabricated at moderate temperatures of 230 degrees C with mobilities of 0.61 cm(2)V(-1)s(-1) and on/off ratios of 3 x 10(5) after postdeposition growth, which is comparable to the characteristics of TFTs fabricated by traditional sputtering methods.

Metallorganic chemical vapor deposition and atomic layer deposition approaches for the growth of hafnium-based thin films from dialkylamide precursors for advanced CMOS gate stack applications

NASA Astrophysics Data System (ADS)

Consiglio, Steven P.

To continue the rapid progress of the semiconductor industry as described by Moore's Law, the feasibility of new material systems for front end of the line (FEOL) process technologies needs to be investigated, since the currently employed polysilicon/SiO2-based transistor system is reaching its fundamental scaling limits. Revolutionary breakthroughs in complementary-metal-oxide-semiconductor (CMOS) technology were recently announced by Intel Corporation and International Business Machines Corporation (IBM), with both organizations revealing significant progress in the implementation of hafnium-based high-k dielectrics along with metal gates. This announcement was heralded by Gordon Moore as "...the biggest change in transistor technology since the introduction of polysilicon gate MOS transistors in the late 1960s." Accordingly, the study described herein focuses on the growth of Hf-based dielectrics and Hf-based metal gates using chemical vapor-based deposition methods, specifically metallorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD). A family of Hf source complexes that has received much attention recently due to their desirable properties for implementation in wafer scale manufacturing is the Hf dialkylamide precursors. These precursors are room temperature liquids and possess sufficient volatility and desirable decomposition characteristics for both MOCVD and ALD processing. Another benefit of using these sources is the existence of chemically compatible Si dialkylamide sources as co-precursors for use in Hf silicate growth. The first part of this study investigates properties of MOCVD-deposited HfO2 and HfSixOy using dimethylamido Hf and Si precursor sources using a customized MOCVD reactor. The second part of this study involves a study of wet and dry surface pre-treatments for ALD growth of HfO2 using tetrakis(ethylmethylamido)hafnium in a wafer scale manufacturing environment. The third part of this study is an investigation of the properties of conductive HfN grown via plasma-assisted atomic layer deposition (PA-ALD) using tetrakis(ethylmethylamido)hafnium on a modified commercially available wafer processing tool. Key properties of these materials for use as gate stack replacement materials are addressed and future directions for further characterization and novel material investigations are proposed.

Electronic-carrier-controlled photochemical etching process in semiconductor device fabrication

DOEpatents

Ashby, C.I.H.; Myers, D.R.; Vook, F.L.

1988-06-16

An electronic-carrier-controlled photochemical etching process for carrying out patterning and selective removing of material in semiconductor device fabrication includes the steps of selective ion implanting, photochemical dry etching, and thermal annealing, in that order. In the selective ion implanting step, regions of the semiconductor material in a desired pattern are damaged and the remainder of the regions of the material not implanted are left undamaged. The rate of recombination of electrons and holes is increased in the damaged regions of the pattern compared to undamaged regions. In the photochemical dry etching step which follows ion implanting step, the material in the undamaged regions of the semiconductor are removed substantially faster than in the damaged regions representing the pattern, leaving the ion-implanted, damaged regions as raised surface structures on the semiconductor material. After completion of photochemical dry etching step, the thermal annealing step is used to restore the electrical conductivity of the damaged regions of the semiconductor material.

Electronic-carrier-controlled photochemical etching process in semiconductor device fabrication

DOEpatents

Ashby, Carol I. H.; Myers, David R.; Vook, Frederick L.

1989-01-01

An electronic-carrier-controlled photochemical etching process for carrying out patterning and selective removing of material in semiconductor device fabrication includes the steps of selective ion implanting, photochemical dry etching, and thermal annealing, in that order. In the selective ion implanting step, regions of the semiconductor material in a desired pattern are damaged and the remainder of the regions of the material not implanted are left undamaged. The rate of recombination of electrons and holes is increased in the damaged regions of the pattern compared to undamaged regions. In the photochemical dry etching step which follows ion implanting step, the material in the undamaged regions of the semiconductor are removed substantially faster than in the damaged regions representing the pattern, leaving the ion-implanted, damaged regions as raised surface structures on the semiconductor material. After completion of photochemical dry etching step, the thermal annealing step is used to restore the electrical conductivity of the damaged regions of the semiconductor material.

Understanding and control of bipolar self-doping in copper nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fioretti, Angela N., E-mail: afiorett@mines.edu, E-mail: riy.zakutayev@nrel.gov; Tamboli, Adele C.; Caskey, Christopher M.

2016-05-14

Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu{sub 3}N) is a metastable semiconductor with a solar-relevant bandgap that has been reported to exhibit bipolar doping behavior. However, deeper understanding and better control of the mechanism behind this behavior in Cu{sub 3}N is currently lacking in the literature. In this work, we use combinatorial growth with a temperature gradient to demonstrate both conduction types of phase-pure, sputter-deposited Cu{sub 3}N thin films. Room temperature Hall effect and Seebeck effect measurements show n-type Cu{sub 3}N with 10{sup 17} electrons/cm{sup 3}more » for low growth temperature (≈35 °C) and p-type with 10{sup 15} holes/cm{sup 3}–10{sup 16} holes/cm{sup 3} for elevated growth temperatures (50 °C–120 °C). Mobility for both types of Cu{sub 3}N was ≈0.1 cm{sup 2}/Vs–1 cm{sup 2}/Vs. Additionally, temperature-dependent Hall effect measurements indicate that ionized defects are an important scattering mechanism in p-type films. By combining X-ray absorption spectroscopy and first-principles defect theory, we determined that V{sub Cu} defects form preferentially in p-type Cu{sub 3}N, while Cu{sub i} defects form preferentially in n-type Cu{sub 3}N, suggesting that Cu{sub 3}N is a compensated semiconductor with conductivity type resulting from a balance between donor and acceptor defects. Based on these theoretical and experimental results, we propose a kinetic defect formation mechanism for bipolar doping in Cu{sub 3}N that is also supported by positron annihilation experiments. Overall, the results of this work highlight the importance of kinetic processes in the defect physics of metastable materials and provide a framework that can be applied when considering the properties of such materials in general.« less

Defect-Induced Nucleation and Epitaxy: A New Strategy toward the Rational Synthesis of WZ-GaN/3C-SiC Core-Shell Heterostructures.

PubMed

Liu, Baodan; Yang, Bing; Yuan, Fang; Liu, Qingyun; Shi, Dan; Jiang, Chunhai; Zhang, Jinsong; Staedler, Thorsten; Jiang, Xin

2015-12-09

In this work, we demonstrate a new strategy to create WZ-GaN/3C-SiC heterostructure nanowires, which feature controllable morphologies. The latter is realized by exploiting the stacking faults in 3C-SiC as preferential nucleation sites for the growth of WZ-GaN. Initially, cubic SiC nanowires with an average diameter of ∼100 nm, which display periodic stacking fault sections, are synthesized in a chemical vapor deposition (CVD) process to serve as the core of the heterostructure. Subsequently, hexagonal wurtzite-type GaN shells with different shapes are grown on the surface of 3C-SiC wire core. In this context, it is possible to obtain two types of WZ-GaN/3C-SiC heterostructure nanowires by means of carefully controlling the corresponding CVD reactions. Here, the stacking faults, initially formed in 3C-SiC nanowires, play a key role in guiding the epitaxial growth of WZ-GaN as they represent surface areas of the 3C-SiC nanowires that feature a higher surface energy. A dedicated structural analysis of the interfacial region by means of high-resolution transmission electron microscopy (HRTEM) revealed that the disordering of the atom arrangements in the SiC defect area promotes a lattice-matching with respect to the WZ-GaN phase, which results in a preferential nucleation. All WZ-GaN crystal domains exhibit an epitaxial growth on 3C-SiC featuring a crystallographic relationship of [12̅10](WZ-GaN) //[011̅](3C-SiC), (0001)(WZ-GaN)//(111)(3C-SiC), and d(WZ-GaN(0001)) ≈ 2d(3C-SiC(111)). The approach to utilize structural defects of a nanowire core to induce a preferential nucleation of foreign shells generally opens up a number of opportunities for the epitaxial growth of a wide range of semiconductor nanostructures which are otherwise impossible to acquire. Consequently, this concept possesses tremendous potential for the applications of semiconductor heterostructures in various fields such as optics, electrics, electronics, and photocatalysis for energy harvesting and environment processing.

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Two-stage liquid phase epitaxy for fabrication of buried InGaAsP/InP heterostructures

NASA Astrophysics Data System (ADS)

Procházková, O.; Novotný, J.; Šrobár, F.

1988-11-01

The technology of growth of buried heterojunction lasers emitting at 1.3 μm and some of their physical properties are described. Mesa stripes 8-μm wide were formed on heteroepitaxial wafers grown by liquid phase epitaxy at 630°C. They were buried by a second process at a lower temperature (590°C). The threshold current was about 100 mA and the temperature sensitivity was characterized by a parameter amounting to about 60 K. Single-mode lasing was observed occasionally.

Solid-State Division progress report for period ending March 31, 1983

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, P.H.; Watson, D.M.

1983-09-01

Progress and activities are reported on: theoretical solid-state physics (surfaces; electronic, vibrational, and magnetic properties; particle-solid interactions; laser annealing), surface and near-surface properties of solids (surface, plasma-material interactions, ion implantation and ion-beam mixing, pulsed-laser and thermal processing), defects in solids (radiation effects, fracture, impurities and defects, semiconductor physics and photovoltaic conversion), transport properties of solids (fast-ion conductors, superconductivity, mass and charge transport in materials), neutron scattering (small-angle scattering, lattice dynamics, magnetic properties, structure and instrumentation), and preparation and characterization of research materials (growth and preparative methods, nuclear waste forms, special materials). (DLC)

Intelligent monitoring and control of semiconductor manufacturing equipment

NASA Technical Reports Server (NTRS)

Murdock, Janet L.; Hayes-Roth, Barbara

1991-01-01

The use of AI methods to monitor and control semiconductor fabrication in a state-of-the-art manufacturing environment called the Rapid Thermal Multiprocessor is described. Semiconductor fabrication involves many complex processing steps with limited opportunities to measure process and product properties. By applying additional process and product knowledge to that limited data, AI methods augment classical control methods by detecting abnormalities and trends, predicting failures, diagnosing, planning corrective action sequences, explaining diagnoses or predictions, and reacting to anomalous conditions that classical control systems typically would not correct. Research methodology and issues are discussed, and two diagnosis scenarios are examined.

Crystallographic alignment of high-density gallium nitride nanowire arrays.

PubMed

Kuykendall, Tevye; Pauzauskie, Peter J; Zhang, Yanfeng; Goldberger, Joshua; Sirbuly, Donald; Denlinger, Jonathan; Yang, Peidong

2004-08-01

Single-crystalline, one-dimensional semiconductor nanostructures are considered to be one of the critical building blocks for nanoscale optoelectronics. Elucidation of the vapour-liquid-solid growth mechanism has already enabled precise control over nanowire position and size, yet to date, no reports have demonstrated the ability to choose from different crystallographic growth directions of a nanowire array. Control over the nanowire growth direction is extremely desirable, in that anisotropic parameters such as thermal and electrical conductivity, index of refraction, piezoelectric polarization, and bandgap may be used to tune the physical properties of nanowires made from a given material. Here we demonstrate the use of metal-organic chemical vapour deposition (MOCVD) and appropriate substrate selection to control the crystallographic growth directions of high-density arrays of gallium nitride nanowires with distinct geometric and physical properties. Epitaxial growth of wurtzite gallium nitride on (100) gamma-LiAlO(2) and (111) MgO single-crystal substrates resulted in the selective growth of nanowires in the orthogonal [1\\[Evec]0] and [001] directions, exhibiting triangular and hexagonal cross-sections and drastically different optical emission. The MOCVD process is entirely compatible with the current GaN thin-film technology, which would lead to easy scale-up and device integration.

Controlled growth of larger heterojunction interface area for organic photosensitive devices

DOEpatents

Yang, Fan [Somerset, NJ; Forrest, Stephen R [Ann Arbor, MI

2009-12-29

An optoelectronic device and a method of fabricating a photosensitive optoelectronic device includes depositing a first organic semiconductor material on a first electrode to form a continuous first layer having protrusions, a side of the first layer opposite the first electrode having a surface area at least three times greater than an underlying lateral cross-sectional area; depositing a second organic semiconductor material directly on the first layer to form a discontinuous second layer, portions of the first layer remaining exposed; depositing a third organic semiconductor material directly on the second layer to form a discontinuous third layer, portions of at least the second layer remaining exposed; depositing a fourth organic semiconductor material on the third layer to form a continuous fourth layer, filling any exposed gaps and recesses in the first, second, and third layers; and depositing a second electrode on the fourth layer, wherein at least one of the first electrode and the second electrode is transparent, and the first and third organic semiconductor materials are both of a donor-type or an acceptor-type relative to second and fourth organic semiconductor materials, which are of the other material type.

A new approximation of Fermi-Dirac integrals of order 1/2 for degenerate semiconductor devices

NASA Astrophysics Data System (ADS)

AlQurashi, Ahmed; Selvakumar, C. R.

2018-06-01

There had been tremendous growth in the field of Integrated circuits (ICs) in the past fifty years. Scaling laws mandated both lateral and vertical dimensions to be reduced and a steady increase in doping densities. Most of the modern semiconductor devices have invariably heavily doped regions where Fermi-Dirac Integrals are required. Several attempts have been devoted to developing analytical approximations for Fermi-Dirac Integrals since numerical computations of Fermi-Dirac Integrals are difficult to use in semiconductor devices, although there are several highly accurate tabulated functions available. Most of these analytical expressions are not sufficiently suitable to be employed in semiconductor device applications due to their poor accuracy, the requirement of complicated calculations, and difficulties in differentiating and integrating. A new approximation has been developed for the Fermi-Dirac integrals of the order 1/2 by using Prony's method and discussed in this paper. The approximation is accurate enough (Mean Absolute Error (MAE) = 0.38%) and easy enough to be used in semiconductor device equations. The new approximation of Fermi-Dirac Integrals is applied to a more generalized Einstein Relation which is an important relation in semiconductor devices.

Submillimeter Spectroscopic Diagnostics in Semiconductor Processing Plasmas

NASA Astrophysics Data System (ADS)

Helal, Yaser H.; Neese, Christopher F.; De Lucia, Frank C.; Ewing, Paul R.; Stout, Phillip J.; Walker, Quentin; Armacost, Michael D.

2014-06-01

Submillimeter absorption spectroscopy was used to study semiconductor processing plasmas. Abundances and temperatures of molecules, radicals, and ions can be determined without altering any of the properties of the plasma. The behavior of these measurements provides useful applications in monitoring process steps. A summary of such applications will be presented, including etching and cleaning endpoint detection.

Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Brebrick, Robert F.; Burger, Arnold; Dudley, Michael; Matyi, Richard J.; Ramachandran, Narayanan; Sha, Yi-Gao; Volz, Martin; Shih, Hung-Dah

2000-01-01

Interest in optical devices which can operate in the visible spectrum has motivated research interest in the II-VI wide band gap semiconductor materials. The recent challenge for semiconductor opto-electronics is the development of a laser which can operate at short visible wavelengths. In the past several years, major advances in thin film technology such as molecular beam epitaxy and metal organic chemical vapor deposition have demonstrated the applicability of II-VI materials to important devices such as light-emitting diodes, lasers, and ultraviolet detectors. With an energy gap of 2.7 eV at room temperature, and an efficient band- to-band transition, ZnSe has been studied extensively as the primary candidate for a blue light emitting diode for optical displays, high density recording, and military communications. By employing a ternary or quaternary system, the energy band gap of II-VI materials can be tuned to a specific range. While issues related to the compositional inhomogeneity and defect incorporation are still to be fully resolved, ZnSe bulk crystals and ZnSe-based heterostructures such as ZnSe/ZnSeS, ZnSe/ZnCdSe and ZnCdSe/ZnSeS have showed photopumped lasing capability in the blue-green region at a low threshold power and high temperatures. The demonstration of its optical bistable properties in bulk and thin film forms also make ZnSe a possible candidate material for the building blocks of a digital optical computer. Despite this, developments in the crystal growth of bulk H-VI semiconductor materials has not advanced far enough to provide the low price, high quality substrates needed for the thin film growth technology.

Modulational instability of helicon waves in a magnetoactive semiconductor n-InSb

NASA Astrophysics Data System (ADS)

Salimullah, M.; Ferdous, T.

1984-03-01

In this paper the modulational instabilithy of a beam of high amplitude helicon wave in a magnetoactive piezoelectric semiconductor is studied. The nonlinear response of electrons in the semiconductor plasma has been found by following the fluid model of homogeneous plasmas. The low frequency nonlinearity has been taken through the ponderomotive force on electrons, whereas the nonlinearity in the scattered helicon waves arises through the nonlinear current densities of electrons. For typical plasma parameters in n-type indium antimonide and for a considerable power density (approximately 20 kW/sq cm) of the incident helicon beam, the growth rate of the modulational instability is quite high (approximately 10 to the 7th rad/s).

Growth Of Organic Semiconductor Thin Films with Multi-Micron Domain Size and Fabrication of Organic Transistors Using a Stencil Nanosieve.

PubMed

Fesenko, Pavlo; Flauraud, Valentin; Xie, Shenqi; Kang, Enpu; Uemura, Takafumi; Brugger, Jürgen; Genoe, Jan; Heremans, Paul; Rolin, Cédric

2017-07-19

To grow small molecule semiconductor thin films with domain size larger than modern-day device sizes, we evaporate the material through a dense array of small apertures, called a stencil nanosieve. The aperture size of 0.5 μm results in low nucleation density, whereas the aperture-to-aperture distance of 0.5 μm provides sufficient crosstalk between neighboring apertures through the diffusion of adsorbed molecules. By integrating the nanosieve in the channel area of a thin-film transistor mask, we show a route for patterning both the organic semiconductor and the metal contacts of thin-film transistors using one mask only and without mask realignment.

Vapor phase growth technique of III-V compounds utilizing a preheating step

NASA Technical Reports Server (NTRS)

Olsen, Gregory Hammond (Inventor); Zamerowski, Thomas Joseph (Inventor); Buiocchi, Charles Joseph (Inventor)

1978-01-01

In the vapor phase epitaxy fabrication of semiconductor devices and in particular semiconductor lasers, the deposition body on which a particular layer of the laser is to be grown is preheated to a temperature about 40.degree. to 60.degree. C. lower than the temperature at which deposition occurs. It has been discovered that by preheating at this lower temperature there is reduced thermal decomposition at the deposition surface, especially for semiconductor materials such as indium gallium phosphide and gallium arsenide phosphide. A reduction in thermal decomposition reduces imperfections in the deposition body in the vicinity of the deposition surface, thereby providing a device with higher efficiency and longer lifetime.

Cadmium Telluride Semiconductor Detector for Improved Spatial and Energy Resolution Radioisotopic Imaging

PubMed Central

Abbaspour, Samira; Mahmoudian, Babak; Islamian, Jalil Pirayesh

2017-01-01

The detector in single-photon emission computed tomography has played a key role in the quality of the images. Over the past few decades, developments in semiconductor detector technology provided an appropriate substitution for scintillation detectors in terms of high sensitivity, better energy resolution, and also high spatial resolution. One of the considered detectors is cadmium telluride (CdTe). The purpose of this paper is to review the CdTe semiconductor detector used in preclinical studies, small organ and small animal imaging, also research in nuclear medicine and other medical imaging modalities by a complete inspect on the material characteristics, irradiation principles, applications, and epitaxial growth method. PMID:28553175

Environment, health and safety issues for sources used in MOVPE growth of compound semiconductors

NASA Astrophysics Data System (ADS)

Shenai-Khatkhate, Deodatta V.; Goyette, Randall J.; DiCarlo, Ronald L., Jr.; Dripps, Gregory

2004-12-01

As metalorganic vapor-phase epitaxy (MOVPE) is becoming well-established production technology, there are equally growing concerns associated with its bearing on personnel and community safety, environmental impact and maximum quantities of hazardous materials permissible in the device fabrication operations. Safety as well as responsible environmental care has always been of paramount importance in the MOVPE-based crystal growth of compound semiconductors. In this paper, we present the findings from workplace exposure monitoring studies on conventional MOVPE sources such as trimethylgallium, triethylgallium, trimethylantimony and diethylzinc. Also reviewed are the environmental, health and safety hazard aspects for metalorganic sources of routine elements, and the means to minimize the risks (i.e., engineering controls) involved while using these MOVPE sources.

Optimization of GaN thin films via MOCVD

NASA Technical Reports Server (NTRS)

Dickens, Corey; Wilson, Sylvia L.

1995-01-01

A unique characteristic of every semiconductor is the amount of energy required to break an electron bond in the lowest band of allowed states, the valence band. The energy necessary to set an electron free and allow it to conduct in the material is termed the energy gap (Eg). Semiconductors with wide bandgap energies have been shown to possess properties for high power, high temperature, radiation resistance damage, and short wavelength optoelectronic applications. Gallium nitride, which has a wide gap of 3.39 eV, is a material that has demonstrated these characteristics. Various growth conditions are being investigated for quality gallium nitride heteroepitaxy growth via the technique of low pressure metal organic chemical vapor deposition (MOCVD) that can be used for device development.

Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Brebrick, R. F.; Burger, A.; Dudley, M.; Matyi, R.; Ramachandran, N.; Sha, Yi-Gao; Volz, M.; Shih, Hung-Dah

1999-01-01

Complete and systematic ground-based experimental and theoretical analyses on the Physical Vapor Transport (PVT) of ZnSe and related ternary compound semiconductors have been performed. The analyses included thermodynamics, mass flux, heat treatment of starting material, crystal growth, partial pressure measurements, optical interferometry, chemical analyses, photoluminescence, microscopy, x-ray diffraction and topography as well as theoretical, analytical and numerical analyses. The experimental results showed the influence of gravity orientation on the characteristics of: (1) the morphology of the as-grown crystals as well as the as-grown surface morphology of ZnSe and Cr doped ZnSe crystals; (2) the distribution of impurities and defects in ZnSe grown crystals; and (3) the axial segregation in ZnSeTe grown crystals.

Roadmap on semiconductor-cell biointerfaces

NASA Astrophysics Data System (ADS)

Tian, Bozhi; Xu, Shuai; Rogers, John A.; Cestellos-Blanco, Stefano; Yang, Peidong; Carvalho-de-Souza, João L.; Bezanilla, Francisco; Liu, Jia; Bao, Zhenan; Hjort, Martin; Cao, Yuhong; Melosh, Nicholas; Lanzani, Guglielmo; Benfenati, Fabio; Galli, Giulia; Gygi, Francois; Kautz, Rylan; Gorodetsky, Alon A.; Kim, Samuel S.; Lu, Timothy K.; Anikeeva, Polina; Cifra, Michal; Krivosudský, Ondrej; Havelka, Daniel; Jiang, Yuanwen

2018-05-01

This roadmap outlines the role semiconductor-based materials play in understanding the complex biophysical dynamics at multiple length scales, as well as the design and implementation of next-generation electronic, optoelectronic, and mechanical devices for biointerfaces. The roadmap emphasizes the advantages of semiconductor building blocks in interfacing, monitoring, and manipulating the activity of biological components, and discusses the possibility of using active semiconductor-cell interfaces for discovering new signaling processes in the biological world.

In Situ Electrochemical Deposition of Microscopic Wires

NASA Technical Reports Server (NTRS)

Yun, Minhee; Myung, Nosang; Vasquez, Richard

2005-01-01

A method of fabrication of wires having micron and submicron dimensions is built around electrochemical deposition of the wires in their final positions between electrodes in integrated circuits or other devices in which the wires are to be used. Heretofore, nanowires have been fabricated by a variety of techniques characterized by low degrees of controllability and low throughput rates, and it has been necessary to align and electrically connect the wires in their final positions by use of sophisticated equipment in expensive and tedious post-growth assembly processes. The present method is more economical, offers higher yields, enables control of wire widths, and eliminates the need for post-growth assembly. The wires fabricated by this method could be used as simple electrical conductors or as transducers in sensors. Depending upon electrodeposition conditions and the compositions of the electroplating solutions in specific applications, the wires could be made of metals, alloys, metal oxides, semiconductors, or electrically conductive polymers. In this method, one uses fabrication processes that are standard in the semiconductor industry. These include cleaning, dry etching, low-pressure chemical vapor deposition, lithography, dielectric deposition, electron-beam lithography, and metallization processes as well as the electrochemical deposition process used to form the wires. In a typical case of fabrication of a circuit that includes electrodes between which microscopic wires are to be formed on a silicon substrate, the fabrication processes follow a standard sequence until just before the fabrication of the microscopic wires. Then, by use of a thermal SiO-deposition technique, the electrodes and the substrate surface areas in the gaps between them are covered with SiO. Next, the SiO is electron-beam patterned, then reactive-ion etched to form channels having specified widths (typically about 1 m or less) that define the widths of the wires to be formed. Drops of an electroplating solution are placed on the substrate in the regions containing the channels thus formed, then the wires are electrodeposited from the solution onto the exposed portions of the electrodes and into the channels. The electrodeposition is a room-temperature, atmospheric-pressure process. The figure shows an example of palladium wires that were electrodeposited into 1-mm-wide channels between gold electrodes.

Electrical properties of solid-solution SrZrxTi1-xO3 grown epitaxially on Ge by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Moghadam, Reza; Ahmadi, Kamyar; Xiao, Z.-Y.; Hong, Xia; Ngai, Joseph

The epitaxial growth of crystalline oxides on semiconductors enables new functionalities to be introduced to semiconductor devices. In particular, dielectric and ferroelectric oxides grown epitaxially on semiconductors provide a pathway to realize ultra-low power logic and memory devices. Here we present electrical characterization of solid-solution SrZrxTi1-xO3 grown epitaxially on Ge through oxide molecular beam epitaxy. SrZrxTi1-xO3 is of particular interest since the band offset with respect to the semiconductor can be tuned through Zr content x. We will present current-voltage, capacitance-voltage and piezoforce microscopy characterization of SrZrxTi1-xO3 -Ge heterojunctions. In particular, we will discuss how the electrical characteristics of SrZrxTi1-xO3 -Ge heterojunctions evolve with respect to composition, annealing and film thickness.

Programmable and coherent crystallization of semiconductors

PubMed Central

Yu, Liyang; Niazi, Muhammad R.; Ngongang Ndjawa, Guy O.; Li, Ruipeng; Kirmani, Ahmad R.; Munir, Rahim; Balawi, Ahmed H.; Laquai, Frédéric; Amassian, Aram

2017-01-01

The functional properties and technological utility of polycrystalline materials are largely determined by the structure, geometry, and spatial distribution of their multitude of crystals. However, crystallization is seeded through stochastic and incoherent nucleation events, limiting the ability to control or pattern the microstructure, texture, and functional properties of polycrystalline materials. We present a universal approach that can program the microstructure of materials through the coherent seeding of otherwise stochastic homogeneous nucleation events. The method relies on creating topographic variations to seed nucleation and growth at designated locations while delaying nucleation elsewhere. Each seed can thus produce a coherent growth front of crystallization with a geometry designated by the shape and arrangement of seeds. Periodic and aperiodic crystalline arrays of functional materials, such as semiconductors, can thus be created on demand and with unprecedented sophistication and ease by patterning the location and shape of the seeds. This approach is used to demonstrate printed arrays of organic thin-film transistors with remarkable performance and reproducibility owing to their demonstrated spatial control over the microstructure of organic and inorganic polycrystalline semiconductors. PMID:28275737

The United States digital recording industry

NASA Technical Reports Server (NTRS)

Simonds, John L.

1993-01-01

The recording industry resembles the semiconductor industry in several aspects. Both are large (greater than $60 Billion/year revenues); both are considered critical technologies supporting national objectives; both are experiencing increased competition from foreign suppliers; they recognize significant opportunities for both technological and market growth in the decade to come; and both realize that a key to this future growth lies in alliances among industry, academia, and government. The semiconductor industry has made significant investments in alliances relating to manufacturing technologies (SEMATECH) and to joint long-term technology research centered in universities (SRC). The federal government has provided funding support of these efforts in recognition of the critical roles semiconductor technologies play in national interests. The recording industry is now also forming critical alliances, but has been slower in starting and in gaining broad recognition by government agencies and legislators that the industry needs federal support. Traditionally, the recording industry has been viewed as mature, stable, and, while critical to national interests, able to chart and fund its own course toward future national needs. That perception is fortunately changing.

/III-V semiconductor broadband distributed Bragg reflectors for long-wavelength VCSEL and SESAM devices

NASA Astrophysics Data System (ADS)

Koeninger, Anna; Boehm, Gerhard; Meyer, Ralf; Amann, Markus-Christian

2014-12-01

Semiconductor devices such as vertical-cavity surface-emitting lasers (VCSELs) or semiconductor-saturable absorber mirrors (SESAMs) require high-reflection mirrors. Moreover, in VCSELs, it is beneficial to have a crystalline mirror, which is as thin as possible in order to ensure a high thermal conductivity for efficient heat-sinking of the laser. On the other hand, the wavelength tuning range of a SESAM is limited by the reflection bandwidth of its distributed Bragg reflector (DBR). Thus, broadband mirrors are preferable here. This paper reports a three-pair DBR grown by molecular beam epitaxy (MBE) using BaCaF2 and GaAs on a GaAs (100) substrate. Due to the high ratio in refractive indices of GaAs and the group-IIa-fluorides, high-reflectivity mirrors and wide bandwidths can be obtained with low total thicknesses. We also investigated growth and stability of the material BaCaF2, as well as its thermal conductivity both as single layer and Bragg reflector. Observed peeling of the layers could be avoided by implementing a fluorine treatment previous to the BaCaF2 growth.

Optimization of the photorefractivity in II-IV semiconductors. Final report, March 1996--March 1997

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jagannathan, G.V.; Trivedi, S.B.; Kutcher, S.W.

1998-11-01

This work was aimed at optimization of the photorefractivity in the II-VI semiconductors CdTe, ZnTe and Cd{sub x{minus}1}Zn{sub (x)}Te for real-time optical signal processing applications at near infrared wavelengths. During this work, several crystals of ZnTe, CdTe and Cd{sub x{minus}1}Zn{sub (x)}Te were grown. Crystal growth of ZnTe and CdTe was carried out using low supersaturation nucleation and `contactless` growth by Vertical Physical Vapor Transport (PVT) in closed ampoules and the CdTe and Cd{sub x{minus}1}Zn{sub (x)}Te crystals were grown using the vertical Bridgman technique. The quality of the crystals grown during this work was evaluated based on optical, electrical and structuralmore » characterization. Infrared microscopy was used to examine the internal crystalline structure of the samples. Most of the crystals grown during this work exhibited photorefractivity and photoconductivity. The resistivity of the vanadium doped crystals under dark conditions was found to be between 10 {sup 8} to 10 {sup 10} ohms cm. The resistivity decreased significantly in the presence of illumination indicating that the crystals were highly photoconductive. The photorefractive properties of the crystals grown during this project were characterized by two beam coupling. All of the measurements revealed a strong photorefractive nonlinear effect.« less

Crystal Growth, Characterization and Fabrication of Cadmium Zinc Telluride-based Nuclear Detectors

NASA Astrophysics Data System (ADS)

Krishna, Ramesh M.

In today's world, nuclear radiation is seeing more and more use by humanity as time goes on. Nuclear power plants are being built to supply humanity's energy needs, nuclear medical imaging is becoming more popular for diagnosing cancer and other diseases, and control of weapons-grade nuclear materials is becoming more and more important for national security. All of these needs require high-performance nuclear radiation detectors which can accurately measure the type and amount of radiation being used. However, most current radiation detection materials available commercially require extensive cooling, or simply do not function adequately for high-energy gamma-ray emitting nuclear materials such as uranium and plutonium. One of the most promising semiconductor materials being considered to create a convenient, field-deployable nuclear detector is cadmium zinc telluride (CdZnTe, or CZT). CZT is a ternary semiconductor compound which can detect high-energy gamma-rays at room temperature. It offers high resistivity (≥ 1010 O-cm), a high band gap (1.55 eV), and good electron transport properties, all of which are required for a nuclear radiation detector. However, one significant issue with CZT is that there is considerable difficulty in growing large, homogeneous, defect-free single crystals of CZT. This significantly increases the cost of producing CZT detectors, making CZT less than ideal for mass-production. Furthermore, CZT suffers from poor hole transport properties, which creates significant problems when using it as a high-energy gamma-ray detector. In this dissertation, a comprehensive investigation is undertaken using a successful growth method for CZT developed at the University of South Carolina. This method, called the solvent-growth technique, reduces the complexity required to grow detector-grade CZT single crystals. It utilizes a lower growth temperature than traditional growth methods by using Te as a solvent, while maintaining the advantages of crystal homogeneity of other modern CZT growth techniques. However, information about crystals grown with this method has not been undertaken in a comprehensive way thus far. In this work, Cd0.9Zn0.1Te is grown using the solvent-growth method using zone-refined precursor materials loaded into carbon-coated quartz ampoules. Ampoules were sealed and crystal growth was performed using crystal growth furnaces built in-house at USC. Ingots 1-2" in diameter produced using the solvent-growth method were wafered, processed, and polished for characterization. Semiconductor characterization is performed on the CZT crystals to determine band gap, elemental stoichiometry, and electrical resistivity. Surface modification studies were undertaken to determine if surface leakage current can be reduced using sulfur passivation. XPS studies were used to confirm the effects of passivation on the surface states, and electrical characterization was performed to measure the effects of passivation on the CZT crystals. Deep-level and surface defect studies were conducted on the CZT samples to determine the type and intensity of defects present in the crystals which may affect detector performance. Finally, nuclear detectors were fabricated and characterized using analog and digital radiation detection systems to measure their performance and energy resolution.

Ionized cluster beam deposition

NASA Technical Reports Server (NTRS)

Kirkpatrick, A. R.

1983-01-01

Ionized Cluster Beam (ICB) deposition, a new technique originated by Takagi of Kyoto University in Japan, offers a number of unique capabilities for thin film metallization as well as for deposition of active semiconductor materials. ICB allows average energy per deposited atom to be controlled and involves impact kinetics which result in high diffusion energies of atoms on the growth surface. To a greater degree than in other techniques, ICB involves quantitative process parameters which can be utilized to strongly control the characteristics of films being deposited. In the ICB deposition process, material to be deposited is vaporized into a vacuum chamber from a confinement crucible at high temperature. Crucible nozzle configuration and operating temperature are such that emerging vapor undergoes supercondensation following adiabatic expansion through the nozzle.

Temperature control of power semiconductor devices in traction applications

NASA Astrophysics Data System (ADS)

Pugachev, A. A.; Strekalov, N. N.

2017-02-01

The peculiarity of thermal management of traction frequency converters of a railway rolling stock is highlighted. The topology and the operation principle of the automatic temperature control system of power semiconductor modules of the traction frequency converter are designed and discussed. The features of semiconductors as an object of temperature control are considered; the equivalent circuit of thermal processes in the semiconductors is suggested, the power losses in the two-level voltage source inverters are evaluated and analyzed. The dynamic properties and characteristics of the cooling fan induction motor electric drive with the scalar control are presented. The results of simulation in Matlab are shown for the steady state of thermal processes.

Scalable fabrication of strongly textured organic semiconductor micropatterns by capillary force lithography.

PubMed

Jo, Pil Sung; Vailionis, Arturas; Park, Young Min; Salleo, Alberto

2012-06-26

Strongly textured organic semiconductor micropatterns made of the small molecule dioctylbenzothienobenzothiophene (C(8)-BTBT) are fabricated by using a method based on capillary force lithography (CFL). This technique provides the C(8)-BTBT solution with nucleation sites for directional growth, and can be used as a scalable way to produce high quality crystalline arrays in desired regions of a substrate for OFET applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zn(1-x)MnxTe diluted magnetic semiconductor nanowires grown by molecular beam epitaxy.

PubMed

Zaleszczyk, Wojciech; Janik, Elzbieta; Presz, Adam; Dłuzewski, Piotr; Kret, Sławomir; Szuszkiewicz, Wojciech; Morhange, Jean-François; Dynowska, Elzbieta; Kirmse, Holm; Neumann, Wolfgang; Petroutchik, Aleksy; Baczewski, Lech T; Karczewski, Grzegorz; Wojtowicz, Tomasz

2008-11-01

It is shown that the growth of II-VI diluted magnetic semiconductor nanowires is possible by the catalytically enhanced molecular beam epitaxy (MBE). Zn(1-x)MnxTe NWs with manganese content up to x=0.60 were produced by this method. X-ray diffraction, Raman spectroscopy, and temperature dependent photoluminescence measurements confirm the incorporation of Mn(2+) ions in the cation substitutional sites of the ZnTe matrix of the NWs.

Recent Vertical External Cavity Surface Emitting Lasers (VECSELs) Developments for Sensor Applications (POSTPRINT)

DTIC Science & Technology

2013-02-01

edge-emitting strained InxGa1−xSb/AlyGa1−ySb quantum well struc- tures using solid-source molecular beam epitaxy (MBE) with varying barrier heights...intersubband quantum wells. The most common high-power edge-emitting semiconductor lasers suffter from poor beam quality, due primarily to the linewidth...reduces the power scalability of semiconductor lasers. In vertical cavity surface emitting lasers ( VCSELs ), light propagates parallel to the growth

Electrical properties of metal/Al2O3/In0.53Ga0.47As capacitors grown on InP

NASA Astrophysics Data System (ADS)

Ferrandis, Philippe; Billaud, Mathilde; Duvernay, Julien; Martin, Mickael; Arnoult, Alexandre; Grampeix, Helen; Cassé, Mikael; Boutry, Hervé; Baron, Thierry; Vinet, Maud; Reimbold, Gilles

2018-04-01

To overcome the Fermi-level pinning in III-V metal-oxide-semiconductor capacitors, attention is usually focused on the choice of dielectric and surface chemical treatments prior to oxide deposition. In this work, we examined the influence of the III-V material surface cleaning and the semiconductor growth technique on the electrical properties of metal/Al2O3/In0.53Ga0.47As capacitors grown on InP(100) substrates. By means of the capacitance-voltage measurements, we demonstrated that samples do not have the same total oxide charge density depending on the cleaning solution used [(NH4)2S or NH4OH] prior to oxide deposition. The determination of the interface trap density revealed that a Fermi-level pinning occurs for samples grown by metalorganic chemical vapor deposition but not for similar samples grown by molecular beam epitaxy. Deep level transient spectroscopy analysis explained the Fermi-level pinning by an additional signal for samples grown by metalorganic chemical vapor deposition, attributed to the tunneling effect of carriers trapped in oxide toward interface states. This work emphasizes that the choice of appropriate oxide and cleaning treatment is not enough to prevent a Fermi-level pinning in III-V metal-oxide-semiconductor capacitors. The semiconductor growth technique needs to be taken into account because it impacts the trapping properties of the oxide.

Producing Silicon Carbide for Semiconductor Devices

NASA Technical Reports Server (NTRS)

Hsu, G. C.; Rohatgi, N. K.

1986-01-01

Processes proposed for production of SiC crystals for use in semiconductors operating at temperatures as high as 900 degrees C. Combination of new processes produce silicon carbide chips containing epitaxial layers. Chips of SiC first grown on porous carbon matrices, then placed in fluidized bed, where additional layer of SiC grows. Processes combined to yield complete process. Liquid crystallization process used to make SiC particles or chips for fluidized-bed process.

Competing Classical and Quantum Effects in Shape Relaxation of a Metallic Nanostructure

NASA Technical Reports Server (NTRS)

Chen, Dongmin; Okamoto, Hiroshi; Yamada, Toshishi; Biegel, Bryan (Technical Monitor)

2003-01-01

We demonstrate for the first time that the quantum size effect (QSE) plays a competing role along side the classical thermodynamic effect in the shape relaxation of a small metallic island. Together, these effects transforms a lead(Pb) island grown on Si(111) substrate from its initially flattop faceted morphology to a peculiar ring-shape island, a process catalysed by the tip electric field of a scanning tunnelling microscope (STM). We shall show for the first time how QSE affects the relaxation process dynamically. In particular, it leads to a novel strip-flow growth and double-step growth on selective strips of a plateau inside the ring, defined by the substrate steps more than 60?0?3 below. It appears that atoms diffusing on the plateau can clearly (sub i)(deg)sense(sub i)+/- the quantized energy states inside the island and have preferentially attached to regions that further reduces the surface energy as a result of the QSE, limiting its own growth and stabilizing the ring shape. The mechanism proposed here offers a sound explanation for ring shape metal and semiconductor islands observed in other systems as well.

Growth-substrate induced performance degradation in chemically synthesized monolayer MoS{sub 2} field effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amani, Matin; Chin, Matthew L.; Mazzoni, Alexander L.

2014-05-19

We report on the electronic transport properties of single-layer thick chemical vapor deposition (CVD) grown molybdenum disulfide (MoS{sub 2}) field-effect transistors (FETs) on Si/SiO{sub 2} substrates. MoS{sub 2} has been extensively investigated for the past two years as a potential semiconductor analogue to graphene. To date, MoS{sub 2} samples prepared via mechanical exfoliation have demonstrated field-effect mobility values which are significantly higher than that of CVD-grown MoS{sub 2}. In this study, we will show that the intrinsic electronic performance of CVD-grown MoS{sub 2} is equal or superior to that of exfoliated material and has been possibly masked by a combinationmore » of interfacial contamination on the growth substrate and residual tensile strain resulting from the high-temperature growth process. We are able to quantify this strain in the as-grown material using pre- and post-transfer metrology and microscopy of the same crystals. Moreover, temperature-dependent electrical measurements made on as-grown and transferred MoS{sub 2} devices following an identical fabrication process demonstrate the improvement in field-effect mobility.« less

Controlling Molecular Doping in Organic Semiconductors.

PubMed

Jacobs, Ian E; Moulé, Adam J

2017-11-01

The field of organic electronics thrives on the hope of enabling low-cost, solution-processed electronic devices with mechanical, optoelectronic, and chemical properties not available from inorganic semiconductors. A key to the success of these aspirations is the ability to controllably dope organic semiconductors with high spatial resolution. Here, recent progress in molecular doping of organic semiconductors is summarized, with an emphasis on solution-processed p-type doped polymeric semiconductors. Highlighted topics include how solution-processing techniques can control the distribution, diffusion, and density of dopants within the organic semiconductor, and, in turn, affect the electronic properties of the material. Research in these areas has recently intensified, thanks to advances in chemical synthesis, improved understanding of charged states in organic materials, and a focus on relating fabrication techniques to morphology. Significant disorder in these systems, along with complex interactions between doping and film morphology, is often responsible for charge trapping and low doping efficiency. However, the strong coupling between doping, solubility, and morphology can be harnessed to control crystallinity, create doping gradients, and pattern polymers. These breakthroughs suggest a role for molecular doping not only in device function but also in fabrication-applications beyond those directly analogous to inorganic doping. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photovoltage field-effect transistors

NASA Astrophysics Data System (ADS)

Adinolfi, Valerio; Sargent, Edward H.

2017-02-01

The detection of infrared radiation enables night vision, health monitoring, optical communications and three-dimensional object recognition. Silicon is widely used in modern electronics, but its electronic bandgap prevents the detection of light at wavelengths longer than about 1,100 nanometres. It is therefore of interest to extend the performance of silicon photodetectors into the infrared spectrum, beyond the bandgap of silicon. Here we demonstrate a photovoltage field-effect transistor that uses silicon for charge transport, but is also sensitive to infrared light owing to the use of a quantum dot light absorber. The photovoltage generated at the interface between the silicon and the quantum dot, combined with the high transconductance provided by the silicon device, leads to high gain (more than 104 electrons per photon at 1,500 nanometres), fast time response (less than 10 microseconds) and a widely tunable spectral response. Our photovoltage field-effect transistor has a responsivity that is five orders of magnitude higher at a wavelength of 1,500 nanometres than that of previous infrared-sensitized silicon detectors. The sensitization is achieved using a room-temperature solution process and does not rely on traditional high-temperature epitaxial growth of semiconductors (such as is used for germanium and III-V semiconductors). Our results show that colloidal quantum dots can be used as an efficient platform for silicon-based infrared detection, competitive with state-of-the-art epitaxial semiconductors.

The Development of III-V Semiconductor MOSFETs for Future CMOS Applications

NASA Astrophysics Data System (ADS)

Greene, Andrew M.

Alternative channel materials with superior transport properties over conventional strained silicon are required for supply voltage scaling in low power complementary metal-oxide-semiconductor (CMOS) integrated circuits. Group III-V compound semiconductor systems offer a potential solution due to their high carrier mobility, low carrier effective mass and large injection velocity. The enhancement in transistor drive current at a lower overdrive voltage allows for the scaling of supply voltage while maintaining high switching performance. This thesis focuses on overcoming several material and processing challenges associated with III-V semiconductor development including a low thermal processing budget, high interface trap state density (Dit), low resistance source/drain contacts and growth on lattice mismatched substrates. Non-planar In0.53Ga0.47As FinFETs were developed using both "gate-first" and "gate-last" fabrication methods for n-channel MOSFETs. Electron beam lithography and anisotropic plasma etching processes were optimized to create highly scaled fins with near vertical sidewalls. Plasma damage was removed using a wet etch process and improvements in gate efficiency were characterized on MOS capacitor structures. A two-step, selective removal of the pre-grown n+ contact layer was developed for "gate-last" recess etching. The final In0.53Ga 0.47As FinFET devices demonstrated an ION = 70 mA/mm, I ON/IOFF ratio = 15,700 and sub-threshold swing = 210 mV/dec. Bulk GaSb and strained In0.36Ga0.64Sb quantum well (QW) heterostructures were developed for p-channel MOSFETs. Dit was reduced to 2 - 3 x 1012 cm-2eV-1 using an InAs surface layer, (NH4)2S passivation and atomic layer deposition (ALD) of Al2O3. A self-aligned "gate-first" In0.36Ga0.64Sb MOSFET fabrication process was invented using a "T-shaped" electron beam resist patterning stack and intermetallic source/drain contacts. Ni contacts annealed at 300°C demonstrated an ION = 166 mA/mm, ION/IOFF ratio = 1,500 and sub-threshold swing = 340 mV/dec. Split C-V measurements were used to extract an effective channel mobility of muh* = 300 cm2/Vs at Ns = 2 x 1012 cm -2. "Gate-last" MOSFETs grown with an epitaxial p + contact layer were fabricated using selective gate-recess etching techniques. A parasitic "n-channel" limited ION/I OFF ratio and sub-threshold swing, most likely due to effects from the InAs surface layer.

A cyano-terminated dithienyldiketopyrrolopyrrole dimer as a solution processable ambipolar semiconductor under ambient conditions.

PubMed

Wang, Li; Zhang, Xiaojie; Tian, Hongkun; Lu, Yunfeng; Geng, Yanhou; Wang, Fosong

2013-12-14

A cyano-terminated dimer of dithienyldiketopyrrolopyrrole (TDPP), DPP2-CN, is a solution processable ambipolar semiconductor with field-effect hole and electron mobilities of 0.066 and 0.033 cm(2) V(-1) s(-1), respectively, under ambient conditions.

A hybrid life cycle inventory of nano-scale semiconductor manufacturing.

PubMed

Krishnan, Nikhil; Boyd, Sarah; Somani, Ajay; Raoux, Sebastien; Clark, Daniel; Dornfeld, David

2008-04-15

The manufacturing of modern semiconductor devices involves a complex set of nanoscale fabrication processes that are energy and resource intensive, and generate significant waste. It is important to understand and reduce the environmental impacts of semiconductor manufacturing because these devices are ubiquitous components in electronics. Furthermore, the fabrication processes used in the semiconductor industry are finding increasing application in other products, such as microelectromechanical systems (MEMS), flat panel displays, and photovoltaics. In this work we develop a library of typical gate-to-gate materials and energy requirements, as well as emissions associated with a complete set of fabrication process models used in manufacturing a modern microprocessor. In addition, we evaluate upstream energy requirements associated with chemicals and materials using both existing process life cycle assessment (LCA) databases and an economic input-output (EIO) model. The result is a comprehensive data set and methodology that may be used to estimate and improve the environmental performance of a broad range of electronics and other emerging applications that involve nano and micro fabrication.

Specific features of doping with antimony during the ion-beam crystallization of silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pashchenko, A. S., E-mail: as.pashchenko@gmail.com; Chebotarev, S. N.; Lunin, L. S.

2016-04-15

A method of doping during the growth of thin films by ion-beam crystallization is proposed. By the example of Si and Sb, the possibility of controllably doping semiconductors during the ion-beam crystallization process is shown. A calibrated temperature dependence of the antimony vapor flow rate in the range from 150 to 400°C is obtained. It is established that, an increase in the evaporator temperature above 200°C brings about the accumulation of impurities in the layer growth direction. Silicon layers doped with antimony to a concentration of 10{sup 18} cm{sup –3} are grown. It is shown that, as the evaporator temperaturemore » is increased, the efficiency of the activation of antimony in silicon nonlinearly decreases from ~10{sup 0} to ~10{sup –3}.« less

In situ growth of lamellar ZnTiO3 nanosheets on TiO2 tubular array with enhanced photocatalytic activity.

PubMed

Cai, Yunyu; Ye, Yixing; Tian, Zhenfei; Liu, Jun; Liu, Yishu; Liang, Changhao

2013-12-14

We report a self-sacrificed in situ growth design toward preparation of ZnTiO3-TiO2 heterojunction structure. Highly reactive zinc oxide colloidal particles derived by laser ablation in liquids can react with TiO2 nanotubes to form a lamellar ZnTiO3 nanosheet structure in a hydrothermal-treatment process. Such hybrid structural product was characterized by X-ray diffraction, scanning and transmission electron microscopy, UV-vis diffuse reflection spectroscopy and X-ray photoelectron spectroscopy. The enhanced photocatalytic activity of the hybrid structure toward degradation of methyl orange (MO) and pentachlorophenol (PCP) molecules was demonstrated and compared with single phase TiO2, as a result of the efficient separation of light excited electrons and holes at the hetero-interfaces in the two semiconductors.

Space- and Ground-Based Crystal Growth Using a Baffle (CGB)

NASA Technical Reports Server (NTRS)

Ostrogorsky, A. G.; Marin, C.; Peignier, T.; Duffar, T.; Volz, M.; Jeter, L.; Luz, P.

2001-01-01

The composition of semiconductor crystals produced in space by conventional melt-growth processes (directional solidification and zone melting) is affected by minute levels of residual micro-acceleration, which causes natural convection. The residual acceleration has random magnitude, direction and frequency. Therefore, the velocity field in the melt is apriori unpredictable. As a result, the composition of the crystals grown in space can not be predicted and reproduced. The method for directional solidification with a submerged heater or a baffle was developed under NASA sponsorship. The disk-shaped baffle acts as a partition, creating a small melt zone at the solid-liquid interface. As a result, in ground based experiment the level of buoyancy-driven convection at the interface is significantly reduced. In several experiments with Te-doped GaSb, nearly diffusion controlled segregation was achieved.

Growth of catalyst-free high-quality ZnO nanowires by thermal evaporation under air ambient

PubMed Central

2012-01-01

ZnO nanowires have been successfully fabricated on Si substrate by simple thermal evaporation of Zn powder under air ambient without any catalyst. Morphology and structure analyses indicated that ZnO nanowires had high purity and perfect crystallinity. The diameter of ZnO nanowires was 40 to 100 nm, and the length was about several tens of micrometers. The prepared ZnO nanowires exhibited a hexagonal wurtzite crystal structure. The growth of the ZnO nanostructure was explained by the vapor-solid mechanism. The simplicity, low cost and fewer necessary apparatuses of the process would suit the high-throughput fabrication of ZnO nanowires. The ZnO nanowires fabricated on Si substrate are compatible with state-of-the-art semiconductor industry. They are expected to have potential applications in functional nanodevices. PMID:22502639

The MSFC complementary metal oxide semiconductor (including multilevel interconnect metallization) process handbook

NASA Technical Reports Server (NTRS)

Bouldin, D. L.; Eastes, R. W.; Feltner, W. R.; Hollis, B. R.; Routh, D. E.

1979-01-01

The fabrication techniques for creation of complementary metal oxide semiconductor integrated circuits at George C. Marshall Space Flight Center are described. Examples of C-MOS integrated circuits manufactured at MSFC are presented with functional descriptions of each. Typical electrical characteristics of both p-channel metal oxide semiconductor and n-channel metal oxide semiconductor discrete devices under given conditions are provided. Procedures design, mask making, packaging, and testing are included.

The AMOS cell - An improved metal-semiconductor solar cell. [Antireflection coated Metal Oxide Semiconductor

NASA Technical Reports Server (NTRS)

Stirn, R. J.; Yeh, Y.-C. M.

1975-01-01

A new fabrication process is being developed which significantly improves the efficiency of metal-semiconductor solar cells. The resultant effect, a marked increase in the open-circuit voltage, is produced by the addition of an interfacial layer oxide on the semiconductor. Cells using gold on n-type gallium arsenide have been made in small areas (0.17 sq cm) with conversion efficiencies of 15% in terrestrial sunlight.

Dry texturing of solar cells

DOEpatents

Sopori, B.L.

1994-10-25

A textured backside of a semiconductor device for increasing light scattering and absorption in a semiconductor substrate is accomplished by applying infrared radiation to the front side of a semiconductor substrate that has a metal layer deposited on its backside in a time-energy profile that first produces pits in the backside surface and then produces a thin, highly reflective, low resistivity, epitaxial alloy layer over the entire area of the interface between the semiconductor substrate and a metal contact layer. The time-energy profile includes ramping up to a first energy level and holding for a period of time to create the desired pit size and density and then rapidly increasing the energy to a second level in which the entire interface area is melted and alloyed quickly. After holding the second energy level for a sufficient time to develop the thin alloy layer over the entire interface area, the energy is ramped down to allow epitaxial crystal growth in the alloy layer. The result is a textured backside on an optically reflective, low resistivity alloy interface between the semiconductor substrate and the metal electrical contact layer. 9 figs.

Dry texturing of solar cells

DOEpatents

Sopori, Bhushan L.

1994-01-01

A textured backside of a semiconductor device for increasing light scattering and absorption in a semiconductor substrate is accomplished by applying infrared radiation to the front side of a semiconductor substrate that has a metal layer deposited on its backside in a time-energy profile that first produces pits in the backside surface and then produces a thin, highly reflective, low resistivity, epitaxial alloy layer over the entire area of the interface between the semiconductor substrate and a metal contact layer. The time-energy profile includes ramping up to a first energy level and holding for a period of time to create the desired pit size and density and then rapidly increasing the energy to a second level in which the entire interface area is melted and alloyed quickly. After holding the second energy level for a sufficient time to develop the thin alloy layer over the entire interface area, the energy is ramped down to allow epitaxial crystal growth in the alloy layer. The result is a textured backside an optically reflective, low resistivity alloy interface between the semiconductor substrate and the metal electrical contact layer.

Semiconductor chips, genes, and stem cells: new wine for new bottles?

PubMed

Rose, Simone A

2012-01-01

This Article analogizes early semiconductor technology and its surrounding economics with isolated genes, stem cells, and related bioproducts, and their surrounding economics, to make the case for sui generis (of its own class) intellectual property protection for isolated bioproducts. Just as early semiconductors failed to meet the patent social bargain requiring novelty and non-obviousness in the 1980s, isolated genes and stem cells currently fail to meet the patent bargain requirements of non-obviousness and eligible subject matter that entitle them to traditional intellectual property protection. Like early semiconductor chip designs, nevertheless, the high cost of upstream bioproduct research and development, coupled with the need to sustain continued economic growth of the biotechnology industry, mandates that Congress provide some level of exclusive rights to ensure continued funding for this research. Sui generis intellectual property protection for isolated bioproducts would preserve the incentive to continue innovation in the field. As illustrated by the semiconductor industry, however, such sui generis protection for this technology must include limitations that address the need to provide an appropriate level of public access to facilitate downstream product development and enrich the public domain.

Selective nanoscale growth of lattice mismatched materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Seung-Chang; Brueck, Steven R. J.

Exemplary embodiments provide materials and methods of forming high-quality semiconductor devices using lattice-mismatched materials. In one embodiment, a composite film including one or more substantially-single-particle-thick nanoparticle layers can be deposited over a substrate as a nanoscale selective growth mask for epitaxially growing lattice-mismatched materials over the substrate.

One-pot size-controlled growth of graphene-encapsulated germanium nanocrystals

NASA Astrophysics Data System (ADS)

Lee, Jae-Hyun; Lee, Eun-Kyung; Kang, Seog-Gyun; Jung, Su-Ho; Son, Seok-Kyun; Nam, Woo Hyun; Kim, Tae-Hoon; Choi, Byong Lyong; Whang, Dongmok

2018-05-01

To realize graphene-encapsulated semiconductor nanocrystals (NCs), an additional graphene coating process, which causes shape destruction and chemical contamination, has so far been inevitable. We report herein one-pot growth of uniform graphene-germanium core-shell nanocrystals (Ge@G NCs) in gram scale by the addition of methane as a carbon source during the thermal pyrolysis of germane. The methane plays a critical role in the growth of the graphene shell, as well as in the determination of the nucleation density and diameter of the NCs, similar to a surfactant in the liquid-phase growth of monodisperse NCs. By adjusting the gas ratio of precursors, a mixture of germane and methane, we can control the size of the Ge@G NCs in the range of ∼5-180 nm. The Ge@G NCs were characterized by various microscopic and spectroscopic tools, which indicated that the Ge core is single crystalline, and is completely covered by the graphene shell. We further investigated the merits of the graphene shell, which can enhance the electrical conductivity of nanocrystalline materials.

Spatial localization of nanoparticle growth in photoinduced nanocomposites

NASA Astrophysics Data System (ADS)

Smirnov, Anton A.; Pikulin, Alexander; Bityurin, Nikita

2018-02-01

Photoinduced nanocomposites are the polymer materials where the nanoparticles can be generated by the light irradiation. The single atoms of metal are formed due to the photoreduction of the metal-containing precursor added to the polymer matrix. Then the atoms precipitate into the nanoparticles (NPs). Similarly, semiconductor NPs are assembled from the monomer species such as CdS, which can be released due to the photodestruction of the appropriate precursor. We analyze theoretically the possibility of spatial confinement of growing nanoparticles in a domain where the elementary species are generated by a three-dimensionally localized source. It is shown that the effective confinement can be achieved only if the size of the generation domain exceeds some critical spatial scale determined by the parameters of the system. The confinement is provided by the trapping of the diffusing elementary species by the growing nanoparticles. The proposed model considers the irreversible particle growth, typical for the noble metals. Both the nucleation and the particle growth processes are suggested to be diffusion controlled.

Cathode Degradation in Thallium Bromide Devices

NASA Astrophysics Data System (ADS)

Datta, Amlan; Motakef, Shariar

2015-06-01

Thallium bromide (TlBr) is a wide bandgap, compound semiconductor with high gamma-ray stopping power and promising physical properties. However, performance degradation and the eventual irreversible failure of TlBr devices can occur rapidly at room temperature, due to “polarization”, caused by the electromigration of Tl+ and Br- ions to the electrical contacts across the device. Using the Accelerated Device Degradation (ADD) experiment, the degradation phenomena in TlBr devices have been visualized and recorded. This paper focuses on “ageing” of the device cathode at various temperatures. ADD is a fast and reliable direct characterization technique that can be used to identify the effects of various growth and post-growth process modifications on device degradation. Using this technique we have identified cathode degradation with the migration of Br- ions and an associated generation and growth of Thallium-rich fractal “ferns” from the cathode. Its effect on the radiation response of the device has also been discussed in this paper. The chemical changes in the cathode were characterized using Energy-dispersive X-ray spectroscopy.

n-Type Doping of Vapor-Liquid-Solid Grown GaAs Nanowires.

PubMed

Gutsche, Christoph; Lysov, Andrey; Regolin, Ingo; Blekker, Kai; Prost, Werner; Tegude, Franz-Josef

2011-12-01

In this letter, n-type doping of GaAs nanowires grown by metal-organic vapor phase epitaxy in the vapor-liquid-solid growth mode on (111)B GaAs substrates is reported. A low growth temperature of 400°C is adjusted in order to exclude shell growth. The impact of doping precursors on the morphology of GaAs nanowires was investigated. Tetraethyl tin as doping precursor enables heavily n-type doped GaAs nanowires in a relatively small process window while no doping effect could be found for ditertiarybutylsilane. Electrical measurements carried out on single nanowires reveal an axially non-uniform doping profile. Within a number of wires from the same run, the donor concentrations ND of GaAs nanowires are found to vary from 7 × 10(17) cm(-3) to 2 × 10(18) cm(-3). The n-type conductivity is proven by the transfer characteristics of fabricated nanowire metal-insulator-semiconductor field-effect transistor devices.

A new direct growth method of graphene on Si-face of 6H-SiC by synergy of the inner and external carbon sources

NASA Astrophysics Data System (ADS)

Yang, Zhiyuan; Xu, Shicai; Zhao, Lili; Zhang, Jing; Wang, Zhengping; Chen, Xiufang; Cheng, Xiufeng; Yu, Fapeng; Zhao, Xian

2018-04-01

Graphene is a promising two-dimensional material that has possible application in various disciplines, due to its super properties, including high carrier mobility, chemical stability, and optical transparency etc. In this paper, we report an inner and external carbon synergy (IECS) method to grow graphene on Si-face of 6H-SiC. This method combined the advantages of chemical vapor deposition (CVD) and traditional epitaxial growth (EG) based on silicon carbide, which providing a feasible approach for growing graphene on the SiC substrates. The graphene was synthesized within just 3 min, which was more than one order of magnitude faster than the graphene grown on 6H-SiC substrates by the traditional EG method. The growth temperature was ∼200 °C lower than the EG process. The directly grown graphene maintained the compatibility with the semiconductor technique, which is benefit for use in graphene-based microelectronic devices.

Formation routes and structural details of the CaF1 layer on Si(111) from high-resolution noncontact atomic force microscopy data

NASA Astrophysics Data System (ADS)

Rahe, Philipp; Smith, Emily F.; Wollschläger, Joachim; Moriarty, Philip J.

2018-03-01

We investigate the CaF1/Si (111 ) interface using a combination of high-resolution scanning tunneling and noncontact atomic force microscopy operated at cryogenic temperature as well as x-ray photoelectron spectroscopy. Submonolayer CaF1 films grown at substrate temperatures between 550 and 600 ∘C on Si (111 ) surfaces reveal the existence of two island types that are distinguished by their edge topology, nucleation position, measured height, and inner defect structure. Our data suggest a growth model where the two island types are the result of two reaction pathways during CaF1 interface formation. A key difference between these two pathways is identified to arise from the excess species during the growth process, which can be either fluorine or silicon. Structural details as a result of this difference are identified by means of high-resolution noncontact atomic force microscopy and add insights into the growth mode of this heteroepitaxial insulator-on-semiconductor system.

The use of metalorganics in the preparation of semiconductor materials. VIII - Feasibility studies of the growth of Group III-Group V compounds of boron by MOCVD

NASA Technical Reports Server (NTRS)

Manasevit, H. M.; Hewitt, W. B.; Nelson, A. J.; Mason, A. R.

1989-01-01

The MOCVD growth of B-As and B-P films on Si, sapphire, and Si-on-sapphire substrates is described; in this process, trimethylborane (TMB) or triethylborane (TEB) is pyrolyzed in the presence of AsH3 or PH3 in an H2 atmosphere. The procedures employed are outlined, and the results are presented in graphs, tables, and micrographs. It is found that the growth rate of the primarily amorphous films is dependent on the TMB or TEB concentration but approximately constant for TEB and AsH3 at 550-900 C. The nominal compositions of films grown using TMB are given as B(12-16)As2 and B(1-1.3)P. Carbon impurities and significant stress, bowing, and crazing are observed in the films grown on Si substrates, with the highest carbon content in the films grown from TMB and PH3.

Multiple sensor multifrequency eddy current monitor for solidification and growth

NASA Technical Reports Server (NTRS)

Wallace, John

1990-01-01

A compact cylindrical multisensor eddy current measuring system with integral furnace was develop to monitor II-VI crystal growth to provide interfacial information, solutal segregation, and conductivities of the growth materials. The use of an array of sensors surrounding the furnace element allows one to monitor the volume of interest. Coupling these data with inverse multifrequency analysis allows radial conductivity profiles to be generated at each sensor position. These outputs were incorporated to control the processes within the melt volume. The standard eddy current system functions with materials whose electric conductivities are as low as 2E2 Mhos/m. A need was seen to extend the measurement range to poorly conducting media so the unit was modified to allow measurement of materials conductivities 4 order of magnitude lower and bulk dielectric properties. Typically these included submicron thick films and semiinsulating GaAs. This system was used to monitor complex heat transfer in grey bodies as well as semiconductor and metallic solidification.

Heteroepitaxial Growth of Germanium-on-Silicon Using Ultrahigh-Vacuum Chemical Vapor Deposition with RF Plasma Enhancement

NASA Astrophysics Data System (ADS)

Alharthi, Bader; Grant, Joshua M.; Dou, Wei; Grant, Perry C.; Mosleh, Aboozar; Du, Wei; Mortazavi, Mansour; Li, Baohua; Naseem, Hameed; Yu, Shui-Qing

2018-05-01

Germanium (Ge) films have been grown on silicon (Si) substrate by ultrahigh-vacuum chemical vapor deposition with plasma enhancement (PE). Argon plasma was generated using high-power radiofrequency (50 W) to assist in germane decomposition at low temperature. The growth temperature was varied in the low range of 250°C to 450°C to make this growth process compatible with complementary metal-oxide-semiconductor technology. The material and optical properties of the grown Ge films were investigated. The material quality was determined by Raman and x-ray diffraction techniques, revealing growth of crystalline films in the temperature range of 350°C to 450°C. Photoluminescence spectra revealed improved optical quality at growth temperatures of 400°C and 450°C. Furthermore, material quality study using transmission electron microscopy revealed existence of defects in the Ge layer grown at 400°C. Based on the etch pit density, the average threading dislocation density in the Ge layer obtained at this growth temperature was measured to be 4.5 × 108 cm-2. This result was achieved without any material improvement steps such as use of graded buffer or thermal annealing. Comparison between PE and non-plasma-enhanced growth, in the same machine at otherwise the same growth conditions, indicated increased growth rate and improved material and optical qualities for PE growth.

Seed-induced growth of flower-like Au-Ni-ZnO metal-semiconductor hybrid nanocrystals for photocatalytic applications.

PubMed

Chen, Yuanzhi; Zeng, Deqian; Cortie, Michael B; Dowd, Annette; Guo, Huizhang; Wang, Junbao; Peng, Dong-Liang

2015-03-25

The combination of metal and semiconductor components in nanoscale to form a hybrid nanocrystal provides an important approach for achieving advanced functional materials with special optical, magnetic and photocatalytic functionalities. Here, a facile solution method is reported for the synthesis of Au-Ni-ZnO metal-semiconductor hybrid nanocrystals with a flower-like morphology and multifunctional properties. This synthetic strategy uses noble and magnetic metal Au@Ni nanocrystal seeds formed in situ to induce the heteroepitaxial growth of semiconducting ZnO nanopyramids onto the surface of metal cores. Evidence of epitaxial growth of ZnO{0001} facets on Ni {111} facets is observed on the heterojunction, even though there is a large lattice mismatch between the semiconducting and magnetic components. Adjustment of the amount of Au and Ni precursors can control the size and composition of the metal core, and consequently modify the surface plasmon resonance (SPR) and magnetic properties. Room-temperature superparamagnetic properties can be achieved by tuning the size of Ni core. The as-prepared Au-Ni-ZnO nanocrystals are strongly photocatalytic and can be separated and re-cycled by virtue of their magnetic properties. The simultaneous combination of plasmonic, semiconducting and magnetic components within a single hybrid nanocrystal furnishes it multifunctionalities that may find wide potential applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Support apparatus for semiconductor wafer processing

DOEpatents

Griffiths, Stewart K.; Nilson, Robert H.; Torres, Kenneth J.

2003-06-10

A support apparatus for minimizing gravitational stress in semiconductor wafers, and particularly silicon wafers, during thermal processing. The support apparatus comprises two concentric circular support structures disposed on a common support fixture. The two concentric circular support structures, located generally at between 10 and 70% and 70 and 100% and preferably at 35 and 82.3% of the semiconductor wafer radius, can be either solid rings or a plurality of spaced support points spaced apart from each other in a substantially uniform manner. Further, the support structures can have segments removed to facilitate wafer loading and unloading. In order to withstand the elevated temperatures encountered during semiconductor wafer processing, the support apparatus, including the concentric circular support structures and support fixture can be fabricated from refractory materials, such as silicon carbide, quartz and graphite. The claimed wafer support apparatus can be readily adapted for use in either batch or single-wafer processors.

Accuracy of existing atomic potentials for the CdTe semiconductor compound

NASA Astrophysics Data System (ADS)

Ward, D. K.; Zhou, X. W.; Wong, B. M.; Doty, F. P.; Zimmerman, J. A.

2011-06-01

CdTe and CdTe-based Cd1-xZnxTe (CZT) alloys are important semiconductor compounds that are used in a variety of technologies including solar cells, radiation detectors, and medical imaging devices. Performance of such systems, however, is limited due to the propensity of nano- and micro-scale defects that form during crystal growth and manufacturing processes. Molecular dynamics simulations offer an effective approach to study the formation and interaction of atomic scale defects in these crystals, and provide insight on how to minimize their concentrations. The success of such a modeling effort relies on the accuracy and transferability of the underlying interatomic potential used in simulations. Such a potential must not only predict a correct trend of structures and energies of a variety of elemental and compound lattices, defects, and surfaces but also capture correct melting behavior and should be capable of simulating crystalline growth during vapor deposition as these processes sample a variety of local configurations. In this paper, we perform a detailed evaluation of the performance of two literature potentials for CdTe, one having the Stillinger-Weber form and the other possessing the Tersoff form. We examine simulations of structures and the corresponding energies of a variety of elemental and compound lattices, defects, and surfaces compared to those obtained from ab initio calculations and experiments. We also perform melting temperature calculations and vapor deposition simulations. Our calculations show that the Stillinger-Weber parameterization produces the correct lowest energy structure. This potential, however, is not sufficiently transferrable for defect studies. Origins of the problems of these potentials are discussed and insights leading to the development of a more transferrable potential suitable for molecular dynamics simulations of defects in CdTe crystals are provided.

A MoTe2-based light-emitting diode and photodetector for silicon photonic integrated circuits.

PubMed

Bie, Ya-Qing; Grosso, Gabriele; Heuck, Mikkel; Furchi, Marco M; Cao, Yuan; Zheng, Jiabao; Bunandar, Darius; Navarro-Moratalla, Efren; Zhou, Lin; Efetov, Dmitri K; Taniguchi, Takashi; Watanabe, Kenji; Kong, Jing; Englund, Dirk; Jarillo-Herrero, Pablo

2017-12-01

One of the current challenges in photonics is developing high-speed, power-efficient, chip-integrated optical communications devices to address the interconnects bottleneck in high-speed computing systems. Silicon photonics has emerged as a leading architecture, in part because of the promise that many components, such as waveguides, couplers, interferometers and modulators, could be directly integrated on silicon-based processors. However, light sources and photodetectors present ongoing challenges. Common approaches for light sources include one or few off-chip or wafer-bonded lasers based on III-V materials, but recent system architecture studies show advantages for the use of many directly modulated light sources positioned at the transmitter location. The most advanced photodetectors in the silicon photonic process are based on germanium, but this requires additional germanium growth, which increases the system cost. The emerging two-dimensional transition-metal dichalcogenides (TMDs) offer a path for optical interconnect components that can be integrated with silicon photonics and complementary metal-oxide-semiconductors (CMOS) processing by back-end-of-the-line steps. Here, we demonstrate a silicon waveguide-integrated light source and photodetector based on a p-n junction of bilayer MoTe 2 , a TMD semiconductor with an infrared bandgap. This state-of-the-art fabrication technology provides new opportunities for integrated optoelectronic systems.

E-beam-pumped semiconductor lasers

NASA Astrophysics Data System (ADS)

Rice, Robert R.; Shanley, James F.; Ruggieri, Neil F.

1995-04-01

The collapse of the Soviet Union opened many areas of laser technology to the West. E-beam- pumped semiconductor lasers (EBSL) were pursued for 25 years in several Soviet Institutes. Thin single crystal screens of II-VI alloys (ZnxCd1-xSe, CdSxSe1-x) were incorporated in laser CRTs to produce scanned visible laser beams at average powers greater than 10 W. Resolutions of 2500 lines were demonstrated. MDA-W is conducting a program for ARPA/ESTO to assess EBSL technology for high brightness, high resolution RGB laser projection application. Transfer of II-VI crystal growth and screen processing technology is underway, and initial results will be reported. Various techniques (cathodoluminescence, one- and two-photon laser pumping, etc.) have been used to assess material quality and screen processing damage. High voltage (75 kV) video electronics were procured in the U.S. to operate test EBSL tubes. Laser performance was documented as a function of screen temperature, beam voltage and current. The beam divergence, spectrum, efficiency and other characteristics of the laser output are being measured. An evaluation of the effect of laser operating conditions upon the degradation rate is being carried out by a design-of-experiments method. An initial assessment of the projected image quality will be performed.

A MoTe2-based light-emitting diode and photodetector for silicon photonic integrated circuits

NASA Astrophysics Data System (ADS)

Bie, Ya-Qing; Grosso, Gabriele; Heuck, Mikkel; Furchi, Marco M.; Cao, Yuan; Zheng, Jiabao; Bunandar, Darius; Navarro-Moratalla, Efren; Zhou, Lin; Efetov, Dmitri K.; Taniguchi, Takashi; Watanabe, Kenji; Kong, Jing; Englund, Dirk; Jarillo-Herrero, Pablo

2017-12-01

One of the current challenges in photonics is developing high-speed, power-efficient, chip-integrated optical communications devices to address the interconnects bottleneck in high-speed computing systems. Silicon photonics has emerged as a leading architecture, in part because of the promise that many components, such as waveguides, couplers, interferometers and modulators, could be directly integrated on silicon-based processors. However, light sources and photodetectors present ongoing challenges. Common approaches for light sources include one or few off-chip or wafer-bonded lasers based on III-V materials, but recent system architecture studies show advantages for the use of many directly modulated light sources positioned at the transmitter location. The most advanced photodetectors in the silicon photonic process are based on germanium, but this requires additional germanium growth, which increases the system cost. The emerging two-dimensional transition-metal dichalcogenides (TMDs) offer a path for optical interconnect components that can be integrated with silicon photonics and complementary metal-oxide-semiconductors (CMOS) processing by back-end-of-the-line steps. Here, we demonstrate a silicon waveguide-integrated light source and photodetector based on a p-n junction of bilayer MoTe2, a TMD semiconductor with an infrared bandgap. This state-of-the-art fabrication technology provides new opportunities for integrated optoelectronic systems.

New method of 2-dimensional metrology using mask contouring

NASA Astrophysics Data System (ADS)

Matsuoka, Ryoichi; Yamagata, Yoshikazu; Sugiyama, Akiyuki; Toyoda, Yasutaka

2008-10-01

We have developed a new method of accurately profiling and measuring of a mask shape by utilizing a Mask CD-SEM. The method is intended to realize high accuracy, stability and reproducibility of the Mask CD-SEM adopting an edge detection algorithm as the key technology used in CD-SEM for high accuracy CD measurement. In comparison with a conventional image processing method for contour profiling, this edge detection method is possible to create the profiles with much higher accuracy which is comparable with CD-SEM for semiconductor device CD measurement. This method realizes two-dimensional metrology for refined pattern that had been difficult to measure conventionally by utilizing high precision contour profile. In this report, we will introduce the algorithm in general, the experimental results and the application in practice. As shrinkage of design rule for semiconductor device has further advanced, an aggressive OPC (Optical Proximity Correction) is indispensable in RET (Resolution Enhancement Technology). From the view point of DFM (Design for Manufacturability), a dramatic increase of data processing cost for advanced MDP (Mask Data Preparation) for instance and surge of mask making cost have become a big concern to the device manufacturers. This is to say, demands for quality is becoming strenuous because of enormous quantity of data growth with increasing of refined pattern on photo mask manufacture. In the result, massive amount of simulated error occurs on mask inspection that causes lengthening of mask production and inspection period, cost increasing, and long delivery time. In a sense, it is a trade-off between the high accuracy RET and the mask production cost, while it gives a significant impact on the semiconductor market centered around the mask business. To cope with the problem, we propose the best method of a DFM solution using two-dimensional metrology for refined pattern.

PREFACE: Semiconductor Nanostructures towards Electronic and Optoelectronic Device Applications II (Symposium K, E-MRS 2009 Spring Meeting)

NASA Astrophysics Data System (ADS)

Nötzel, Richard

2009-07-01

This volume of IOP Conference Series: Materials Science and Engineering contains papers that were presented at the special symposium K at the EMRS 2009 Spring Meeting held 8-12 June in Strasbourg, France, which was entitled 'Semiconductor Nanostructures towards Electronic and Optoelectronic Device Applications II'. Thanks to the broad interest a large variety of quantum dots and quantum wires and related nanostructures and their application in devices could be covered. There was significant progress in the epitaxial growth of semiconductor quantum dots seen in the operation of high-power, as well as mode locked laser diodes and the lateral positioning of quantum dots on patterned substrates or by selective area growth for future single quantum dot based optoelectronic and electronic devices. In the field of semiconductor nanowires high quality, almost twin free structures are now available together with a new degree of freedom for band structure engineering based on alternation of the crystal structure. In the search for Si based light emitting structures, nanocrystals and miniband-related near infrared luminescence of Si/Ge quantum dot superlattices with high quantum efficiency were reported. These highlights, among others, and the engaged discussions of the scientists, engineers and students brought together at the symposium emphasize how active the field of semiconductor nanostructures and their applications in devices is, so that we can look forward to the progress to come. Guest Editor Richard Nötzel COBRA Research Institute Department of Applied Physics Eindhoven University of Technology 5600 MB Eindhoven The Netherlands Tel.: +31 40 247 2047; fax: +31 40 246 1339 E-mail address: r.noetzel@tue.nl

Guided Growth of Horizontal p-Type ZnTe Nanowires

PubMed Central

2016-01-01

A major challenge toward large-scale integration of nanowires is the control over their alignment and position. A possible solution to this challenge is the guided growth process, which enables the synthesis of well-aligned horizontal nanowires that grow according to specific epitaxial or graphoepitaxial relations with the substrate. However, the guided growth of horizontal nanowires was demonstrated for a limited number of materials, most of which exhibit unintentional n-type behavior. Here we demonstrate the vapor–liquid–solid growth of guided horizontal ZnTe nanowires and nanowalls displaying p-type behavior on four different planes of sapphire. The growth directions of the nanowires are determined by epitaxial relations between the nanowires and the substrate or by a graphoepitaxial effect that guides their growth along nanogrooves or nanosteps along the surface. We characterized the crystallographic orientations and elemental composition of the nanowires using transmission electron microscopy and photoluminescence. The optoelectronic and electronic properties of the nanowires were studied by fabricating photodetectors and top-gate thin film transistors. These measurements showed that the guided ZnTe nanowires are p-type semiconductors and are photoconductive in the visible range. The guided growth of horizontal p-type nanowires opens up the possibility of parallel nanowire integration into functional systems with a variety of potential applications not available by other means. PMID:27885331

Guided Growth of Horizontal p-Type ZnTe Nanowires.

PubMed

Reut, Gilad; Oksenberg, Eitan; Popovitz-Biro, Ronit; Rechav, Katya; Joselevich, Ernesto

2016-08-04

A major challenge toward large-scale integration of nanowires is the control over their alignment and position. A possible solution to this challenge is the guided growth process, which enables the synthesis of well-aligned horizontal nanowires that grow according to specific epitaxial or graphoepitaxial relations with the substrate. However, the guided growth of horizontal nanowires was demonstrated for a limited number of materials, most of which exhibit unintentional n-type behavior. Here we demonstrate the vapor-liquid-solid growth of guided horizontal ZnTe nanowires and nanowalls displaying p-type behavior on four different planes of sapphire. The growth directions of the nanowires are determined by epitaxial relations between the nanowires and the substrate or by a graphoepitaxial effect that guides their growth along nanogrooves or nanosteps along the surface. We characterized the crystallographic orientations and elemental composition of the nanowires using transmission electron microscopy and photoluminescence. The optoelectronic and electronic properties of the nanowires were studied by fabricating photodetectors and top-gate thin film transistors. These measurements showed that the guided ZnTe nanowires are p-type semiconductors and are photoconductive in the visible range. The guided growth of horizontal p-type nanowires opens up the possibility of parallel nanowire integration into functional systems with a variety of potential applications not available by other means.

Vertically aligned GaAs nanowires on graphite and few-layer graphene: generic model and epitaxial growth.

PubMed

Munshi, A Mazid; Dheeraj, Dasa L; Fauske, Vidar T; Kim, Dong-Chul; van Helvoort, Antonius T J; Fimland, Bjørn-Ove; Weman, Helge

2012-09-12

By utilizing the reduced contact area of nanowires, we show that epitaxial growth of a broad range of semiconductors on graphene can in principle be achieved. A generic atomic model is presented which describes the epitaxial growth configurations applicable to all conventional semiconductor materials. The model is experimentally verified by demonstrating the growth of vertically aligned GaAs nanowires on graphite and few-layer graphene by the self-catalyzed vapor-liquid-solid technique using molecular beam epitaxy. A two-temperature growth strategy was used to increase the nanowire density. Due to the self-catalyzed growth technique used, the nanowires were found to have a regular hexagonal cross-sectional shape, and are uniform in length and diameter. Electron microscopy studies reveal an epitaxial relationship of the grown nanowires with the underlying graphitic substrates. Two relative orientations of the nanowire side-facets were observed, which is well explained by the proposed atomic model. A prototype of a single GaAs nanowire photodetector demonstrates a high-quality material. With GaAs being a model system, as well as a very useful material for various optoelectronic applications, we anticipate this particular GaAs nanowire/graphene hybrid to be promising for flexible and low-cost solar cells.

Cancer mortality among US workers employed in semiconductor wafer fabrication.

PubMed

Boice, John D; Marano, Donald E; Munro, Heather M; Chadda, Bandana K; Signorello, Lisa B; Tarone, Robert E; Blot, William J; McLaughlin, Joseph K

2010-11-01

To evaluate potential cancer risks in the US semiconductor wafer fabrication industry. A cohort of 100,081 semiconductor workers employed between 1968 and 2002 was studied. Standardized mortality ratios and relative risks (RRs) were estimated. Standardized mortality ratios were similar and significantly low among fabrication and nonfabrication workers for all causes (0.54 and 0.54) and all cancers (0.74 and 0.72). Internal comparisons also showed similar overall cancer risks among fabrication workers (RR = 0.98), including process equipment operators and process equipment service technicians (OP/EST) employed in cleanrooms (RR = 0.97), compared with nonfabrication workers. Nonsignificantly elevated RRs were observed for a few cancer sites among OP/EST workers, but the numbers of deaths were small and there were no trends of increasing risk with duration of employment. Work in the US semiconductor industry, including semiconductor wafer fabrication in cleanrooms, was not associated with increased cancer mortality overall or mortality from any specific form of cancer. However, due to the young average age of this cohort and its associated relatively low numbers of deaths, regular mortality updates of this semiconductor worker cohort are warranted.

Semiconductor Crystal Growth in Static and Rotating Magnetic fields

NASA Technical Reports Server (NTRS)

Volz, Martin

2004-01-01

Magnetic fields have been applied during the growth of bulk semiconductor crystals to control the convective flow behavior of the melt. A static magnetic field established Lorentz forces which tend to reduce the convective intensity in the melt. At sufficiently high magnetic field strengths, a boundary layer is established ahead of the solid-liquid interface where mass transport is dominated by diffusion. This can have a significant effect on segregation behavior and can eliminate striations in grown crystals resulting from convective instabilities. Experiments on dilute (Ge:Ga) and solid solution (Ge-Si) semiconductor systems show a transition from a completely mixed convective state to a diffusion-controlled state between 0 and 5 Tesla. In HgCdTe, radial segregation approached the diffusion limited regime and the curvature of the solid-liquid interface was reduced by a factor of 3 during growth in magnetic fields in excess of 0.5 Tesla. Convection can also be controlled during growth at reduced gravitational levels. However, the direction of the residual steady-state acceleration vector can compromise this effect if it cannot be controlled. A magnetic field in reduced gravity can suppress disturbances caused by residual transverse accelerations and by random non-steady accelerations. Indeed, a joint program between NASA and the NHMFL resulted in the construction of a prototype spaceflight magnet for crystal growth applications. An alternative to the suppression of convection by static magnetic fields and reduced gravity is the imposition of controlled steady flow generated by rotating magnetic fields (RMF)'s. The potential benefits of an RMF include homogenization of the melt temperature and concentration distribution, and control of the solid-liquid interface shape. Adjusting the strength and frequency of the applied magnetic field allows tailoring of the resultant flow field. A limitation of RMF's is that they introduce deleterious instabilities above a critical magnetic field value. Growth conditions in which static magnetic fields rotational magnetic fields, and reduced gravitational levels can have a beneficial role will be described.

Screenable contact structure and method for semiconductor devices

DOEpatents

Ross, Bernd

1980-08-26

An ink composition for deposition upon the surface of a semiconductor device to provide a contact area for connection to external circuitry is disclosed, the composition comprising an ink system containing a metal powder, a binder and vehicle, and a metal frit. The ink is screened onto the semiconductor surface in the desired pattern and is heated to a temperature sufficient to cause the metal frit to become liquid. The metal frit dissolves some of the metal powder and densifies the structure by transporting the dissolved metal powder in a liquid sintering process. The sintering process typically may be carried out in any type of atmosphere. A small amount of dopant or semiconductor material may be added to the ink systems to achieve particular results if desired.

Skylab experiments. Volume 3: Materials science. [Skylab experiments on metallurgy, crystal growth, semiconductors, and combustion physics in weightless environment for high school level education

NASA Technical Reports Server (NTRS)

1973-01-01

The materials science and technology investigation conducted on the Skylab vehicle are discussed. The thirteen experiments that support these investigations have been planned to evaluate the effect of a weightless environment on melting and resolidification of a variety of metals and semiconductor crystals, and on combustion of solid flammable materials. A glossary of terms which define the space activities and a bibliography of related data are presented.

Refractive Index of III-metal-polar and N-polar AlGaN Waveguides Grown by Metal Organic Chemical Vapor Deposition

DTIC Science & Technology

2013-06-03

traditional birefringent materials is the wide bandgap semiconductor AlGaN. This semiconductor belongs to the 6 mm point group, and thus, has five non...effi- ciency of the SHG structure. As the two different polar surfa- ces incorporate point defects at a different rate during growth,25,26 the...diffraction in a triple axis geometry to determine the c-lattice parameter through the use of the (002) symmetric reflection and relating it to com

Semiconductor nanowhiskers: Synthesis, properties, and applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubrovskii, V. G., E-mail: dubrovskii@mail.ioffe.ru; Cirlin, G. E., E-mail: Cirlin@beam.ioffe.ru; Ustinov, V. M., E-mail: Vmust@beam.ioffe.ru

2009-12-15

Recent results of studying the semiconductor's whisker nanocrystals are reviewed. Physical grounds of growing whisker nanocrystals using the mechanism vapor-liquid-crystal are given and the main epitaxial technologies of synthesis of whisker nanocrystals are described. Thermodynamic and kinetic factors controlling the morphological properties, composition, and crystal structure of whisker nanocrystals are considered in detail. The main theoretical models of the growth and structure of whisker nanocrystals are described. The data on physical properties of whisker nanocrystals and possibilities of their use in nanophotonics, nanoelectronics, and nanobiotechnology are presented.

Quantum theory of the electronic and optical properties of low-dimensional semiconductor systems

NASA Astrophysics Data System (ADS)

Lau, Wayne Heung

This thesis examines the electronic and optical properties of low-dimensional semiconductor systems. A theory is developed to study the electron-hole generation-recombination process of type-II semimetallic semiconductor heterojunctions based on a 3 x 3 k·p matrix Hamiltonian (three-band model) and an 8 x 8 k·p matrix Hamiltonian (eight-band model). A novel electron-hole generation and recombination process, which is called activationless generation-recombination process, is predicted. It is demonstrated that the current through the type-II semimetallic semiconductor heterojunctions is governed by the activationless electron-hole generation-recombination process at the heterointerfaces, and that the current-voltage characteristics are essentially linear. A qualitative agreement between theory and experiments is observed. The numerical results of the eight-band model are compared with those of the threeband model. Based on a lattice gas model, a theory is developed to study the influence of a random potential on the ionization equilibrium conditions for bound electron-hole pairs (excitons) in III--V semiconductor heterostructures. It is demonstrated that ionization equilibrium conditions for bound electron-hole pairs change drastically in the presence of strong disorder. It is predicted that strong disorder promotes dissociation of excitons in III--V semiconductor heterostructures. A theory of polariton (photon dressed by phonon) spontaneous emission in a III--V semiconductor doped with semiconductor quantum dots (QDs) or quantum wells (QWs) is developed. For the first time, superradiant and subradiant polariton spontaneous emission phenomena in a polariton-QD (QW) coupled system are predicted when the resonance energies of the two identical QDs (QWs) lie outside the polaritonic energy gap. It is also predicted that when the resonance energies of the two identical QDs (QWs) lie inside the polaritonic energy gap, spontaneous emission of polariton in the polariton-QD (QW) coupled system is inhibited and polariton bound states are formed within the polaritonic energy gap. A theory is also developed to study the polariton eigenenergy spectrum, polariton effective mass, and polariton spectral density of N identical semiconductor QDs (QWs) or a superlattice (SL) placed inside a III--V semiconductor. A polariton-impurity band lying within the polaritonic energy gap of the III--V semiconductor is predicted when the resonance energies of the QDs (QWs) lie inside the polaritonic energy gap. Hole-like polariton effective mass of the polariton-impurity band is predicted. It is also predicted that the spectral density of the polariton has a Lorentzian shape if the resonance energies of the QDs (QWs) lie outside the polaritonic gap.

Final Technical Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Lian

2017-03-08

Our BES supported program integrates molecular beam epitaxy growth with in situ atomic scale imaging using scanning tunneling microscopy/spectroscopy and atomic force microscopy. Aided by density functional theory calculations, we explore enhanced functionalities emerging from the interplay of strain, proximity, and spin-orbit interactions in heterostructures of wide band gap semiconductors, graphene, and Dirac materials, focusing on three thrusts: 1) doping wide bandgap semiconductors and graphene; 2) graphene nanoribbons and graphene-semiconductor heterostructures; and 3) Dirac materials. Our findings and discoveries have led to the publication of one book chapter and twenty-three refereed journal articles, including several in high impact journals suchmore » as Nature Communications, Physical Review Letters, and Nano Letters. Highlights of each thrust are provided in the report.« less

Recent progress in high-mobility thin-film transistors based on multilayer 2D materials

NASA Astrophysics Data System (ADS)

Hong, Young Ki; Liu, Na; Yin, Demin; Hong, Seongin; Kim, Dong Hak; Kim, Sunkook; Choi, Woong; Yoon, Youngki

2017-04-01

Two-dimensional (2D) layered semiconductors are emerging as promising candidates for next-generation thin-film electronics because of their high mobility, relatively large bandgap, low-power switching, and the availability of large-area growth methods. Thin-film transistors (TFTs) based on multilayer transition metal dichalcogenides or black phosphorus offer unique opportunities for next-generation electronic and optoelectronic devices. Here, we review recent progress in high-mobility transistors based on multilayer 2D semiconductors. We describe the theoretical background on characterizing methods of TFT performance and material properties, followed by their applications in flexible, transparent, and optoelectronic devices. Finally, we highlight some of the methods used in metal-semiconductor contacts, hybrid structures, heterostructures, and chemical doping to improve device performance.

Micro-Raman spectroscopy as a tool for the characterization of silicon carbide in power semiconductor material processing

NASA Astrophysics Data System (ADS)

De Biasio, M.; Kraft, M.; Schultz, M.; Goller, B.; Sternig, D.; Esteve, R.; Roesner, M.

2017-05-01

Silicon carbide (SiC) is a wide band-gap semi-conductor material that is used increasingly for high voltage power devices, since it has a higher breakdown field strength and better thermal conductivity than silicon. However, in particular its hardness makes wafer processing difficult and many standard semi-conductor processes have to be specially adapted. We measure the effects of (i) mechanical processing (i.e. grinding of the backside) and (ii) chemical and thermal processing (i.e. doping and annealing), using confocal microscopy to measure the surface roughness of ground wafers and micro-Raman spectroscopy to measure the stresses induced in the wafers by grinding. 4H-SiC wafers with different dopings were studied before and after annealing, using depth-resolved micro-Raman spectroscopy to observe how doping and annealing affect: i.) the damage and stresses induced on the crystalline structure of the samples and ii.) the concentration of free electrical carriers. Our results show that mechanical, chemical and thermal processing techniques have effects on this semiconductor material that can be observed and characterized using confocal microscopy and high resolution micro Raman spectroscopy.

Photoreflectance for in-situ characterization of MOCVD growth of semiconductors under micro-gravity conditions

NASA Technical Reports Server (NTRS)

Pollak, Fred H.

1990-01-01

A contactless electromodulation technique of photoreflectance (PR) was developed for in-situ monitoring of metal-organic chemical vapor deposition (MOCVD) semiconductor growth for micro-gravity applications. PR can be employed in a real MOCVD reactor including rotating substrate (approximately 500 rev/min) in flowing gases and through a diffuser plate. Measurements on GaAs and Ga(0.82)Al(0.18)As were made up to 690 C. The direct band gaps of In(x)Ga(1-x)As (x = 0.07 and 0.16) were evaluated up to 600 C. In order to address the question of real time measurement, the spectra of the direct gap of GaAs at 650 C was obtained in 30 seconds and 15 seconds seems feasible.

Crystal growth of hexaferrite architecture for magnetoelectrically tunable microwave semiconductor integrated devices

NASA Astrophysics Data System (ADS)

Hu, Bolin

Hexaferrites (i.e., hexagonal ferrites), discovered in 1950s, exist as any one of six crystallographic structural variants (i.e., M-, X-, Y-, W-, U-, and Z-type). Over the past six decades, the hexaferrites have received much attention owing to their important properties that lend use as permanent magnets, magnetic data storage materials, as well as components in electrical devices, particularly those operating at RF frequencies. Moreover, there has been increasing interest in hexaferrites for new fundamental and emerging applications. Among those, electronic components for mobile and wireless communications especially incorporated with semiconductor integrated circuits at microwave frequencies, electromagnetic wave absorbers for electromagnetic compatibility, random-access memory (RAM) and low observable technology, and as composite materials having low dimensions. However, of particular interest is the magnetoelectric (ME) effect discovered recently in the hexaferrites such as SrScxFe12-xO19 (SrScM), Ba2--xSrxZn 2Fe12O22 (Zn2Y), Sr4Co2Fe 36O60 (Co2U) and Sr3Co2Fe 24O41 (Co2Z), demonstrating ferroelectricity induced by the complex internal alignment of magnetic moments. Further, both Co 2Z and Co2U have revealed observable magnetoelectric effects at room temperature, representing a step toward practical applications using the ME effect. These materials hold great potential for applications, since strong magnetoelectric coupling allows switching of the FE polarization with a magnetic field (H) and vice versa. These features could lead to a new type of storage devices, such as an electric field-controlled magnetic memory. A nanoscale-driven crystal growth of magnetic hexaferrites was successfully demonstrated at low growth temperatures (25--40% lower than the temperatures required often for crystal growth). This outcome exhibits thermodynamic processes of crystal growth, allowing ease in fabrication of advanced multifunctional materials. Most importantly, the crystal growth technique is considered theoretically and experimentally to be universal and suitable for the growth of a wide range of diverse crystals. In the present experiment, the conical spin structure of Co2Y ferrite crystals were a found to give rise to an intrinsic magnetoelectric effect. Our experiment reveals a remarkable increase in the conical phase transition temperature by ~150 K for Co 2Y ferrite, compared to 5--10 K of Zn2Y ferrites recently reported. The high quality Co2Y ferrite crystals, having low microwave loss and magnetoelectricity, were successfully grown on wide bandgap semiconductor GaN. The demonstration of the nanostructure materials-based "system on a wafer" architecture is a critical milestone to next generation microwave integrated systems. It is also practical that future microwave integrated systems and their magnetic performances could be tuned by an electric field because of the magnetoelectricity of hexaferrites.

Electron-phonon interaction, transport and ultrafast processes in semiconductor microstructures

NASA Astrophysics Data System (ADS)

Sarma, Sankar D.

1992-08-01

We have fulfilled our contract obligations completely by doing theoretical research on electron-phonon interaction and transport properties in submicron semiconductor structures with the emphasis on ultrafast processes and many-body effects. Fifty-five papers have been published based on our research during the contract period.

Centro-Apical Self-Organization of Organic Semiconductors in a Line-Printed Organic Semiconductor: Polymer Blend for One-Step Printing Fabrication of Organic Field-Effect Transistors

PubMed Central

Jin Lee, Su; Kim, Yong-Jae; Young Yeo, So; Lee, Eunji; Sun Lim, Ho; Kim, Min; Song, Yong-Won; Cho, Jinhan; Ah Lim, Jung

2015-01-01

Here we report the first demonstration for centro-apical self-organization of organic semiconductors in a line-printed organic semiconductor: polymer blend. Key feature of this work is that organic semiconductor molecules were vertically segregated on top of the polymer phase and simultaneously crystallized at the center of the printed line pattern after solvent evaporation without an additive process. The thickness and width of the centro-apically segregated organic semiconductor crystalline stripe in the printed blend pattern were controlled by varying the relative content of the organic semiconductors, printing speed, and solution concentrations. The centro-apical self-organization of organic semiconductor molecules in a printed polymer blend may be attributed to the combination of an energetically favorable vertical phase-separation and hydrodynamic fluids inside the droplet during solvent evaporation. Finally, a centro-apically phase-separated bilayer structure of organic semiconductor: polymer blend was successfully demonstrated as a facile method to form the semiconductor and dielectric layer for OFETs in one- step. PMID:26359068

Centro-Apical Self-Organization of Organic Semiconductors in a Line-Printed Organic Semiconductor: Polymer Blend for One-Step Printing Fabrication of Organic Field-Effect Transistors.

PubMed

Lee, Su Jin; Kim, Yong-Jae; Yeo, So Young; Lee, Eunji; Lim, Ho Sun; Kim, Min; Song, Yong-Won; Cho, Jinhan; Lim, Jung Ah

2015-09-11

Here we report the first demonstration for centro-apical self-organization of organic semiconductors in a line-printed organic semiconductor: polymer blend. Key feature of this work is that organic semiconductor molecules were vertically segregated on top of the polymer phase and simultaneously crystallized at the center of the printed line pattern after solvent evaporation without an additive process. The thickness and width of the centro-apically segregated organic semiconductor crystalline stripe in the printed blend pattern were controlled by varying the relative content of the organic semiconductors, printing speed, and solution concentrations. The centro-apical self-organization of organic semiconductor molecules in a printed polymer blend may be attributed to the combination of an energetically favorable vertical phase-separation and hydrodynamic fluids inside the droplet during solvent evaporation. Finally, a centro-apically phase-separated bilayer structure of organic semiconductor: polymer blend was successfully demonstrated as a facile method to form the semiconductor and dielectric layer for OFETs in one- step.

Strain-Driven Stacking Faults in CdSe/CdS Core/Shell Nanorods.

PubMed

Demortière, Arnaud; Leonard, Donovan N; Petkov, Valeri; Chapman, Karena; Chattopadhyay, Soma; She, Chunxing; Cullen, David A; Shibata, Tomohiro; Pelton, Matthew; Shevchenko, Elena V

2018-04-19

Colloidal semiconductor nanocrystals are commonly grown with a shell of a second semiconductor material to obtain desired physical properties, such as increased photoluminescence quantum yield. However, the growth of a lattice-mismatched shell results in strain within the nanocrystal, and this strain has the potential to produce crystalline defects. Here, we study CdSe/CdS core/shell nanorods as a model system to investigate the influence of core size and shape on the formation of stacking faults in the nanocrystal. Using a combination of high-angle annular dark-field scanning transmission electron microscopy and pair-distribution-function analysis of synchrotron X-ray scattering, we show that growth of the CdS shell on smaller, spherical CdSe cores results in relatively small strain and few stacking faults. By contrast, growth of the shell on larger, prolate spheroidal cores leads to significant strain in the CdS lattice, resulting in a high density of stacking faults.