CARBON-REDUCTION IN TRIETHYLARSENIC-GROWN GAAS FILMS USING CHEMICALLY ACTIVATED ARSINE AS A COREAGENT

N-type gallium arsenide films grown from triethylarsenic (Et3As) and trimethylgallium (Me3Ga) are generally of poor quality (μ77K(max) = 16,100 cm2/V-s) and are severely contaminated with carbon (>1018 cm-3), whereas films grown using a mixture of triethylarsenic and arsine (AsH3) with Me3Ga are typically of high purity (β77K(max) = 60,000 cm2/V-s) and contain significantly reduced carbon levels (~mid-1015 cm-3). These differences in film purity are due to the inherent growth chemistry of each reagent mixture. The respective growth chemistries of these reagent systems have been inferred from a series of decomposition experiments carried out under pseudo-growth conditions, and the differences in growth chemistry are consistent with the differences in corresponding epilayer purity. Triethylarsenic appears to decompose primarily via a bond homolysis reaction to generate alkyl-containing radical species, which can react with a growing GaAs epilayer to cause severe carbon contamination. In the Et3As/AsH3 coreagent system, the Et3As reagent decomposes to produce these alkyl-containing radical intermediates, but they then apparently react further with the arsine co-reagent to generate reactive arsenic hydride radicals under relatively facile conditions. These reactive arsenic-hydride radical species can contribute to the GaAs growth process without introducing carbon into the resultant films. © 1990 The Mineral, Metal & Materials Society, Inc.