Growth and properties of InGaAs/FeAl/InAlAs/InP heterostructures for buried reflector/interconnect applications in InGaAs thermophotovoltaic devices
- Department of Electrical Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)
- Bettis Atomic Power Laboratory, West Mifflin, Pennsylvania 15122 (United States)
InGaAs thermophotovoltaic cells are of extreme promise for high efficiency, low bandgap TPV conversion. In the monolithic interconnected module scheme, an InGaAs lateral conduction layer (LCL) is used for the series connection between TPV cells results in undesirable free carrier absorption, causing a tradeoff between series resistance and optical absorption losses in the infrared. A potential alternative is to replace the LCL with an epitaxial metal layer that would provide a low-resistance interconnect while not suffering from free carrier absorption. The internal metal layer would also serve as an efficient, panchromatic back surface reflector, providing the additional advantage of increased effective optical thickness of the InGaAs cell. In this paper, we present the first results on the growth and development of buried epitaxial metal layers for TPV applications. High quality, single crystal, epitaxial Fe{sub x}Al{sub 1{minus}x} layers were grown on InAlAs/InP substrates, having compositions in the range x=0.40{endash}0.80. Epitaxial metal layers up to 1000 {Angstrom} in thickness were achieved, with excellent uniformity over large areas and atomically smooth surfaces. X-ray diffraction studies indicate that all FeAl layers are strained with respect to the substrate, for the entire composition range studied and, surprisingly, for all thicknesses. The FeAl layers exhibit excellent resistance characteristics, with resistivities from 60 {mu}ohm-cm to 100 {mu}ohm-cm being measured for layers having thickness greater than 200 {Angstrom}. This closely matches bulk FeAl resistivity values, indicating that interface scattering has a negligible effect on lateral conductivity. Reflectance measurements show that the FeAl thickness must be at least 1000 {Angstrom} to achieve {gt}90{percent} reflection in the infrared. Overgrowth of InGaAs and AlInAs on FeAl surfaces was achieved, with layer quality depending strongly on As overpressure, possibly due to In segregation to the FeAl surface. {copyright} {ital 1999 American Institute of Physics.}
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 700924
- Report Number(s):
- CONF-981055-; ISSN 0094-243X; TRN: 9913M0004
- Journal Information:
- AIP Conference Proceedings, Vol. 460, Issue 1; Conference: 4. National Renewable Energy Laboratory (NREL) conference on thermophotovoltaic generation of electricity, Denver, CO (United States), 11-14 Oct 1998; Other Information: PBD: Mar 1999
- Country of Publication:
- United States
- Language:
- English
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