The preparation and properties of vapor-grown In/1-x/Ga/x/P
Single crystal indium gallium phosphide p-n junction preparation by epitaxial vapor phase growth technique, determining energy gap dependence on alloy composition
Clough, R. B.↗
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Validation Report for the EO-1 Lightweight Flexible Solar Array Experiment
The controlled deployment of the Lightweight Flexible Solar Array (LFSA) experiment using the shape memory alloy release and deployment system has been demonstrated. Work remains to be done in increasing the efficiency of Copper Indium Diselinide (CIS) terminations to the flexible harness that carries current from the array to the I-V measurement electronics.
Carpenter, Bernie↗
Computed Tomography Support for Microgravity Materials Science Experiments
The accurate measurement of density in both liquid and solid samples is of considerable interest to Principal Investigators with materials science experiments slated for the ISS. The work to be described is an innovative application of a conventional industrial nondestructive evaluation instrument. Traditional applications of industrial computed tomography (CT) rely on reconstructing cross sections of large structures to provide two-dimensional planar views which can identify defects such as porosity, or other material anomalies. This has been done on microgravity materials science experiments to check the integrity of ampoule-cartridge assemblies for safety purposes. With a substantially monoenergetic flux, as can be obtained with a radioactive cobalt source, there will be a direct correlation between absorption and density. Under such conditions it then becomes possible to make accurate measurements of density throughout a sample, and even when the sample itself is enclosed within a furnace and a safety required cartridge. Such a system has been installed at Kennedy Space Center (KSC) and is available to PIs to examine samples before and after flight. The CT system is being used to provide density information for two purposes. Firstly, the determination of density changes from liquid to solid is vital information to the PI for purposes of modeling the solidification behavior of his sample, and to engineers who have to design containment ampoules and must allow for shrinkage and other volume changes that may occur during processing. While such information can be obtained by pycnometric measurements, the possibility of using a furnace installed on the CT system enables one to examine potentially dangerous materials having high vapor pressures, while not needing visible access to the material. In addition, uniform temperature can readily be obtained, and the system can be controlled to ramp up, hold, and ramp down while collecting data over a wide range of parameters automatically. Results of initial tests on low melting point elements such as gallium, indium and tin will be presented, and the intent is to proceed to compounds such as InSb, HgCdTe and CdTe. Alloys such as Pb-Sb (PI - Poirier, U AZ) and Cu-Al (PI - Trivedi, Ames Lab.), which are the subjects of flight experiments, will also be examined. The second application is the conversion of measured density values directly to composition. This was successfully done with the mercury cadmium telluride alloys grown on the second and fourth United States Microgravity Payload (USMP-2 and USMP-4) missions by Lehoczky. CdTe values along the length of the boules were obtained at KSC prior to cutting the sample, and could have been obtained prior to its removal from the cartridge and ampoule. Examples of the data obtained will be shown. It is anticipated that several of the materials science PIs will avail themselves of the technique described, initially for determining densities prior to flight, and then to acquire early quantitative data on the compositional variation within their samples.
Gillies, Donald C.↗
Advances in thin-film solar cells for lightweight space photovoltaic power
The present stature and current research directions of photovoltaic arrays as primary power systems for space are reviewed. There have recently been great advances in the technology of thin-film solar cells for terrestrial applications. In a thin-film solar cell the thickness of the active element is only a few microns; transfer of this technology to space arrays could result in ultralow-weight solar arrays with potentially large gains in specific power. Recent advances in thin-film solar cells are reviewed, including polycrystalline copper-indium selenide (CuInSe2) and related I-III-VI2 compounds, polycrystalline cadmium telluride and related II-VI compounds, and amorphous silicon:hydrogen and alloys. The best experimental efficiency on thin-film solar cells to date is 12 percent AMO for CuIn Se2. This efficiency is likely to be increased in the next few years. The radiation tolerance of thin-film materials is far greater than that of single-crystal materials. CuIn Se2 shows no degradation when exposed to 1 MeV electrons. Experimental evidence also suggests that most of all of the radiation damage on thin-films can be removed by a low temperature anneal. The possibility of thin-film multibandgap cascade solar cells is discussed, including the tradeoffs between monolithic and mechanically stacked cells. The best current efficiency for a cascade is 12.5 percent AMO for an amorphous silicon on CuInSe2 multibandgap combination. Higher efficiencies are expected in the future. For several missions, including solar-electric propulsion, a manned Mars mission, and lunar exploration and manufacturing, thin-film photovolatic arrays may be a mission-enabling technology.
Landis, Geoffrey A.↗
High-performance, flexible, deployable array development for space applications
Flexible, deployable arrays are an attractive alternative to conventional solar arrays for near-term and future space power applications, particularly due to their potential for high specific power and low storage volume. Combined with low-cost flexible thin-film photovoltaics, these arrays have the potential to become an enabling or an enhancing technology for many missions. In order to expedite the acceptance of thin-film photovoltaics for space applications, however, parallel development of flexible photovoltaics and the corresponding deployable structure is essential. Many innovative technologies must be incorporated in these arrays to ensure a significant performance increase over conventional technologies. For example, innovative mechanisms which employ shape memory alloys for storage latches, deployment mechanisms, and array positioning gimbals can be incorporated into flexible array design with significant improvement in the areas of cost, weight, and reliability. This paper discusses recent activities at Martin Marietta regarding the development of flexible, deployable solar array technology. Particular emphasis is placed on the novel use of shape memory alloys for lightweight deployment elements to improve the overall specific power of the array. Array performance projections with flexible thin-film copper-indium-diselenide (CIS) are presented, and government-sponsored solar array programs recently initiated at Martin Marietta through NASA and Air Force Phillips Laboratory are discussed.
Gehling, Russell N.↗
Crystal growth of compound semiconductors in a low-gravity environment (InGaAs crystals) (M-22)
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.
Tatsumi, Masami↗
Solidification of hypermonotectic Al-In alloys under microgravity conditions
Four samples of the Al-In system having monotectic and hypermonotectic compositions that were solidified under microgravity during the NASA-SPAR IX flight of January 20, 1981, are considered. The experimental thermal and physicochemical conditions that were actually achieved are analyzed. Radiographic and metallographic observations of the samples reveal a nonregular dispersed primary phase inside the monotectic matrix. These observations are discussed in relation to capillarity and solidification aspects. A key finding is the preservation of a certain degree of dispersion of the indium primary phase. This result differs fundamentally from the results obtained under microgravity conditions on the same system and compositions (Gelles and Markworth, 1980; Alborn and Loehberg, 1979). The results are seen as clearly establishing that the space environment can be used to obtain dispersed structures from hypermonotectic alloys.
Potard, C.↗
Strained quantum well photovoltaic energy converter
An indium phosphide photovoltaic cell is provided where one or more quantum wells are introduced between the conventional p-conductivity and n-conductivity indium phosphide layer. The approach allows the cell to convert the light over a wider range of wavelengths than a conventional single junction cell and in particular convert efficiently transparency losses of the indium phosphide conventional cell. The approach hence may be used to increase the cell current output. A method of fabrication of photovoltaic devices is provided where ternary InAsP and InGaAs alloys are used as well material in the quantum well region and results in an increase of the cell current output.
Freundlich, Alexandre↗
Small Business Innovations (Photodetector)
Epitaxx, Inc. of Princeton, NJ, developed the Epitaxx Near Infrared Room Temperature Indium-Gallium-Arsenide (InGaAs) Photodetector based on their Goddard Space Flight Center Small Business Innovation Research (SBIR) contract work to develop a linear detector array for satellite imaging applications using InGaAs alloys that didn't need to be cooled to (difficult and expensive) cryogenic temperatures. The photodetectors can be used for remote sensing, fiber optic and laser position-sensing applications.
Source record↗
Visible light electroluminescent diodes of indium-gallium phosphide
Vapor deposition and acceptor impurity diffusion techniques are used to prepare indium-gallium phosphide junctions. Certain problems in preparation are overcome by altering gas flow conditions and by increasing the concentration of phosphine in the gas. A general formula is given for the alloy's composition.
Clough, R.↗
Advanced Materials and Manufacturing for Low-Cost, High-Performance Liquid Rocket Combustion Chambers
A document describes the low-cost manufacturing of C103 niobium alloy combustion chambers, and the use of a high-temperature, oxidation-resistant coating that is superior to the standard silicide coating. The manufacturing process involved low-temperature spray deposition of C103 on removable plastic mandrels produced by rapid prototyping. Thin, vapor-deposited platinum-indium coatings were shown to substantially improve oxidation resistance relative to the standard silicide coating. Development of different low-cost plastic thrust chamber mandrel materials and prototyping processes (selective laser sintering and stereolithography) yielded mandrels with good dimensional accuracy (within a couple of mils) for this stage of development. The feasibility of using the kinetic metallization cold-spray process for fabrication of free-standing C1O3 thrusters on removable plastic mandrels was also demonstrated. The ambient and elevated temperature mechanical properties of the material were shown to be reasonably good relative to conventionally processed C103, but the greatest potential benefit is that coldsprayed chambers require minimal post-process machining, resulting in substantially lower machining and material costs. The platinum-iridium coating was shown to provide greatly increased oxidation resistance over the silicide when evaluated through oxyacetylene torch testing to as high as 300 F (= 150 C). The iridium component minimizes reaction with the niobium alloy chamber at high temperatures, and provides the high-temperature oxidation resistance needed at the throat.
Williams, Brian E.↗
MISSE 6, 7 and 8 Materials Sample Experiments from the International Space Station Materials and Processes Team
The International Space Station Materials and Processes (ISS M&P) team has multiple material samples on MISSE 6, 7 and 8 to observe Low Earth Orbit (LEO) environmental effects on Space Station materials. Optical properties, thickness/mass loss, surface elemental analysis, visual and microscopic analysis for surface change are some of the techniques employed in this investigation. The ISS M&P team has participated in previous MISSE activities in order to better characterize the LEO effects on Space Station materials. This investigation will further this effort. Results for the following MISSE 6 samples materials will be presented: a comparison of anodize and chemical conversion coatings on various aluminum alloys, electroless nickel; AZ93 white ceramic thermal control coating with and without Teflon; Hyzod(TM) polycarbonate used to temporarily protect ISS windows; Russian quartz window material; reformulated Teflon (TM) coated Beta Cloth (Teflon TM without perfluorooctanoic acid (PFOA)) and a Dutch version of beta cloth. Discussion for current and future MISSE materials experiments will be presented. MISSE 7 samples are: deionized water sealed anodized aluminum Photofoil(TM); indium tin oxide (ITO)- coated Kapton(TM) used as thermo-optical surfaces; mechanically scribed tin-plated beryllium-copper samples for "tin pest" growth ( alpha/Beta transformation); Crew Exploration Vehicle (CEV) parachute soft goods. MISSE 8 sample: exposed "scrim cloth" (fiberglass weave) from the ISS solar array wing material, Davlyn fiberglass sleeve material, Permacel and Intertape protective tapes, and ITO-coated Kapton.
Kravchenko, Michael↗
Crystal Growth in the SUBSA furnace in MSG: 2002 to 2022
In 2002, the investigation “Solidification Using a Baffle In Sealed Ampoules (SUBSA)” was the first investigation to utilize the Microgravity Science Glovebox (MSG) Facility on the International Space Station (ISS). The SUBSA furnace was designed for growth of indium antimonide. It features a transparent section, which allows a side view of the melt, the solid-liquid (SL) interface and the growing crystal. In 2002, four Te-doped and three Zn-doped InSb crystals were grown in microgravity. Subsequently, the SUBSA furnace was used in several materials science investigations, including growing the radiation detector materials, InI and Cs2LiYCl6:Ce from the melt and vapor phase (2017 to 2019) and “Brazing of Aluminum alloys in Space (BRAINS)”. A review of the SUBSA furnace features and parameters will be presented, including the design of the growth ampoules, charge preparation, and the procedures used to grow InSb (in 2002) and InI (in 2019).
Aleksandar Ostrogorsky↗
Crystal Growth in the SUBSA furnace at the International Space Station (ISS)
In 2002, our investigation Solidification Using a Baffle In Sealed Ampoules (SUBSA) was the first investigation to utilize the Microgravity Science Glovebox (MSG) Facility on the International Space Station (ISS). The SUBSA furnace was designed for growth of indium antimonide. It features a transparent section, which allows a side view of the melt, the solid-liquid (SL) interface and the growing crystal. In 2002, four Te- doped and three Zn-doped InSb crystals were grown in microgravity. Subsequently, the SUBSA furnace was used in several other materials science investigations, including growing the radiation detector materials InI and Cs2LiYCl6:Ce from the melt and vapor phase (2017 to 2019) and Brazing of Aluminum alloys in Space (BRAINS). A review of the SUBSA furnace features and parameters will be presented, including the design of the growth ampoules, charge preparation, and the procedures used to grow InSb (in 2002) and InI (in 2019).
A.G. Ostrogorsk↗
Triple and Quadruple Junctions Thermophotovoltaic Devices Lattice Matched to InP
Thermophotovoltaic (TPV) conversion of IR radiation emanating from a radioisotope heat source is under consideration for deep space exploration. Ideally, for radiator temperatures of interest, the TPV cell must convert efficiently photons in the 0.4-0.7 eV spectral range. Best experimental data for single junction cells are obtained for lattice-mismatched 0.55 eV InGaAs based devices. It was suggested, that a tandem InGaAs based TPV cell made by monolithically combining two or more lattice mismatched InGaAs subcells on InP would result in a sizeable efficiency improvement. However, from a practical standpoint the implementation of more than two subcells with lattice mismatch systems will require extremely thick graded layers (defect filtering systems) to accommodate the lattice mismatch between the sub-cells and could detrimentally affect the recycling of the unused IR energy to the emitter. A buffer structure, consisting of various InPAs layers, is incorporated to accommodate the lattice mismatch between the high and low bandgap subcells. There are evidences that the presence of the buffer structure may generate defects, which could extend down to the underlying InGaAs layer. The unusual large band gap lowering observed in GaAs(1-x)N(x) with low nitrogen fraction [1] has sparked a new interest in the development of dilute nitrogen containing III-V semiconductors for long-wavelength optoelectronic devices (e.g. IR lasers, detector, solar cells) [2-7]. Lattice matched Ga1-yInyNxAs1-x on InP has recently been investigated for the potential use in the mid-infrared device applications [8], and it could be a strong candidate for the applications in TPV devices. This novel quaternary alloy allows the tuning of the band gap from 1.42 eV to below 1 eV on GaAs and band gap as low as 0.6eV when strained to InP, but it has its own limitations. To achieve such a low band gap using the quaternary Ga1-yInyNxAs1-x, either it needs to be strained on InP, which creates further complications due to the creation of defects and short life of the device or to introduce high content of indium, which again is found problematic due to the difficulties in diluting nitrogen in the presence of high indium [9]. An availability of material of proper band gap and lattice matching on InP are important issues for the development of TPV devices to perform better. To address those issues, recently we have shown that by adjusting the thickness of individual sublayers and the nitrogen composition, strain balanced GaAs(1-x)N(x)/InAs(1-y)N(y) superlattice can be designed to be both lattice matched to InP and have an effective bandgap in the desirable 0.4- 0.7eV range [10,11]. Theoretically the already reduced band gap of GaAs(1-x)N(x), due to the nitrogen effects, can be further reduced by subjecting it to a biaxial tensile strain, for example, by fabricating pseudomorphically strained layers on commonly available InP substrates. While such an approach in principle could allow access to smaller band gap (longer wavelength), only a few atomic monolayers of the material can be grown due to the large lattice mismatch between GaAs(1-x)N(x) and InP (approx.3.8-4.8 % for x<0.05, 300K). This limitation can be avoided using the principle of strain balancing [12], by introducing the alternating layers of InAs(1-y)N(y) with opposite strain (approx.2.4-3.1% for x<0.05, 300K) in combination with GaAs(1-x)N(x). Therefore, even an infinite pseudomorphically strained superlattice thickness can be realized from a sequence of GaAs(1-x)N(x) and InAs(1-y)N(y) layers if the thickness of each layer is kept below the threshold for its lattice relaxation
Bhusal, L.↗
Toward the Development of Group III-V Photodetectors and Imaging Arrays
A collaboration between researchers at NASA Goddard Space Flight Center (GSFC) (Code 718.1) and the Johns Hopkins University Applied Physics Laboratory (APL) on the development of gallium nitride (GaN) based photodetectors has been in existence since July 1994. This collaboration, based on APL undertaking the material growth and GSFC undertaking the device processing, has led to discrete GaN photoconductive detectors with superior characteristics to those of similar devices reported in the literature and, more recently, to the development of state-of-the art 256x256 imaging arrays with the pixels indium bump-bonded to a silicon readout circuit (RIOC). The object of this proposal is to continue the collaboration for the period 1998-2002 by outlining a program of work at the APL on the metalorganic chemical vapor deposition (MOCVD) growth of GaN and related materials for UV detector applications. In particular, emphasis will be placed on the optimization of growth on 2 in diameter substrates, on the growth of In(sub x)Ga(1-x)N and Al(sub x)Ga(1-x)N alloy structures to produce devices with a wider range of tailored cut-off wavelengths, and on the growth of pn-junction structures for photovoltaic devices.
Wickenden, Dennis K.↗
Characterization of Oscillation Modes in Levitated Droplets Using Image and Non-Image Based Techniques
The dynamics of levitated liquid droplets can be used to measure their thermophysical properties by correlating the frequencies at which normal modes of oscillation most strongly resonate when subject to an external oscillatory force. In two preliminary works, it was shown via electrostatic levitation and processing of various metals and alloys that 1) the resonance of the first principal mode of oscillation (mode n = 2) can be used to accurately measure surface tension and 2) that so-called ‘higher-order resonance’ of n = 3 is observable at a predictable frequency. It was also shown, in the context of future space-based experimentation on the Electrostatic Levitation Furnace (ELF), a setup on the International Space Station (ISS) operated by Japan Aerospace Exploration Agency (JAXA), that while the shadow array method in which droplet behavior is visualized would be challenging to identify the n = 3 resonance, the normal mode n = 4 was predicted to be more easily identifiable. In this short communication, experimental evidence of the first three principal modes of oscillation is provided using molten samples of Tin and Indium and it is subsequently shown that, as predicted, an “image-less” approach can be used to identify both n = 2 and n = 4 resonances in levitated liquid droplets. This suggests that the shadow array method may be satisfactorily used to obtain a self-consistent benchmark of thermophysical properties by comparing results from two successive even-mode natural frequencies.
Nevin Brosius↗
Temperature Dependence of Diffusivities in Liquid Elements (LMD)
This research was to advance the understanding of diffusion mechanisms in liquid metals and alloys through accurate diffusivity measurements over a wide range of temperatures, including the proximity of the materials melting points. Specifically, it was driven towards developing a methodology (and subsequent flight hardware) to enable several diffusion coefficient measurements (i.e., at several different temperatures) to be performed using a single sample. The Liquid Metal Diffusion (LMD) was funded as a Flight Definition Project in February 1993 in response to NRA 91-OSSA-20 (Microgravity Science and Applications Division). The Science Concept Review for LAID was held during April 1994. In January 1995 we were informed that we had failed this review and the project was change to ground-based activities only. A new proposal was submitted for the next NRA addressing the panels concerns. As part of NASA's Risk Mitigation program, a scaled-down version of the hardware was funded in July of 1995 for a flight opportunity utilizing experiment on the Microgravity Isolation Mount. This experiment was to determine the self-diffusivity of indium at 185 C. The LMD was transferred to the Mir Space Station in STS-81 and returned on STS-84 (January - May 1997). Three, out of five, self-diffusion data sets were returned. A description of this experiment/hardware is included below. This summary is only intended to give the reader an overview of the results obtained for the tasks outlined in the original proposal. Research that was not published is explained in more detail. At the end of this report is a list of refereed publications and invited talks that were given as a result of this work. The reader is directed to these for further details. Attachment: Real-time diffusivity measurements in liquids at several temperatures with one sample, On the insensitivity of liquid diffusivity measurements to deviations from 1D transport, and Numerical simulations of the convective contamination of diffusivity measurements in liquids.
Banish, R. Michael↗