Thin films of gallium arsenide on low-cost substrates. Quarterly technical progress report No. 5 and topical report No. 1, October 2, 1977-December 31, 1977

The metalorganic chemical vapor deposition (MO-CVD) technique has been applied to the growth of thin films of GaAs and GaAlAs on inexpensive polycrystalline or amorphous substrate materials (primarily glasses and metals) for use in fabrication of large-area low-cost photovoltaic device structures. Trimethylgallium (TMG), arsine (AsH/sub 3/), and trimethylaluminum (TMAl) are mixed in appropriate concentrations at room temperature in the gaseous state and pyrolyzed at the substrate, which is heated in a vertical reactor chamber to temperatures of 725 to 750/sup 0/C, to produce the desired film composition and properties. The substrates used during the quarter included composite structure of sputtered Mo films on various glasses, composites of CVD (GeH/sub 4/ pyrolysis) Ge films of these same glasses, large-grained annealed bulk Mo sheet, large-grained bulk polycrystalling GaAs, and one grade of high-purity high-density graphite. The glasses used were Corning Codes 0317, 7059, and 1723, with most of the composites involving the 0317 type. Preliminary results with graphite substrates were not encouraging, but the available substrates used were not of adequate purity or surface quality. Results are discussed. (WHK)