Interface reactions and grain growth processes in poly-GaAs deposited on molybdenum substrates by the organometallic process

Abstract

This paper describes grain growth processes for polycrystalline gallium arsenide on molybdenum substrates. Growth was carried out by the pyrolytic decomposition of trimethylgallium and arsine in hydrogen. The ability of the organometallic process to allow the growth of gallium arsenide over a wide temperature range is exploited in the initial nucleation and growth phase to obtain full coverage of the substrate. A heat treatment step is used to provide grain expansion and results in a surface with a rippled character. We propose that this comes about by the dissociation of GaAs at the interface, due to strong Mo-As reactions at the annealing temperature, resulting in regrowth of GaAs from a liquid-like phase. Eventual growth of a device quality, active layer is accomplished by conventional CVD growth at 650–700°C, resulting in an average grain size of 6 μm for a 6–7 μm thick overall structure.