We have developed multijunction monolithic interconnected module (MIM) InGaAs/InP structures for thermophotovoltaic (TPV) applications. Murray, David Riley, Westinghouse Electric Corporation, West Mifflin, PA and David Scheiman, NYMA, Inc., Brook Park, OH. Hoffman, Jr., Essential Research, Inc., Cleveland, OH Christopher S. Wilt, NASA Lewis Research Center, Cleveland, OH Phillip P. Fatemi, Essential Research, Inc., Cleveland, OH David M. MULTIJUNCTION InGaAs THERMOPHOTOVOLTAIC DEVICES. We will show that both hydrides are effective at removing carbon from the surface of Ge and that extended exposure of the Ge surface to indium precursors has a detrimental effect on the morphology and defect structure of the heteroepilayer. We also present studies of the initial stages of the nucleation on Ge(100) surfaces and examine the similarities and differences between PH3 and AsH3. Arsine suppresses this ``surface melting'' and enhances the rate of the reverse reaction (disordered surface to ordered surface) by almost an order of magnitude.
Above 570C (in H2), the surface becomes optically and structurally isotropic, i.e. Annealed at temperatures below 57010C in H2, the Ge(100) surface slowly develops a preference for single-domain 1x2 terraces separated by a/2 steps where a is the unit cell dimension of Ge with AsH3 this reaction is much faster. In this paper we first examine the state of the initial Ge(100) surface in various AsH3/PH3/H2 atmospheres using LEED, AES and STM to interpret the in situ RD spectra. The MOCVD apparatus is also equipped with reflectance difference spectroscopy (RDS) and laser light scattering. The analytical chamber is equipped with scanning tunneling microscopy (STM), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES). Recently we have coupled an MOCVD apparatus to a conventional solid source MBE system and an analytical chamber via a UHV transfer chamber. While much is known about the Ge(100) surface in a UHV/MBE environment, little has been published about this surface in an MOCVD environment.
Virtually all of these devices are grown on Ge substrates. GaAs single junction and GaInP/GaAs tandem solar cells are currently being produced by MOCVD on a large scale for communication satellite power applications. McMahon, National Renewable Energy Laboratory, Golden, CO. Rommel Noufi, National Renewable Energy Laboratoryīhushan Sopori, National Renewable Energy Laboratory Symposium Support
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