Epitaxial Growth of GaAs with (C₂H₅)₂GaCl and AsH₃ in a Hotwall Reactor

Abstract

The metalorganic vapor phase epitaxy (MOVPE) of GaAs in a hotwall reactor has been investigated using the growth precursors diethylgalliumchloride [(C2H5)2GaCl, DEGaCl], AsH3, and the carrier gases H2 or He. The growth temperature range of 350 < T < 700°C was investigated at reactor pressures of 0.10-10 torr. Selective growth was achieved on SiNx masked substrates at temperatures of 400°C and above throughout the reactor pressure range of investigation. Significant differences in growth characteristics of the hotwall reactor were observed with respect to a coldwall reactor: the growth rate was reaction rate-limited only at very low temperatures and a precipitous drop in growth rate was observed at high temperatures. At low growth temperatures these differences are ascribed to a change in the growth reaction rate due to distinct group III-growth species in the two reactors configurations, and at high growth temperatures to a shift in the group V growth species from AsH3 to As4 in the HW reactor. The growth mechanism is essentially independent of the carrier gas. The electrical characteristics of the deposited GaAs were n-type throughout the range of growth parameters and demonstrated a minimum in the electron concentration of ≃2 x 1015 cm-3 at 550-600°C. Secondary ion mass spectroscopy identified the dominant impurity concentrations in the grown material at high growth temperatures to be Si, and at low growth temperatures, S. These and additional Sn and Zn impurities are attributed to the DEGaCl source material. Quantitative agreement was found between the electron concentration and the sum of the S and Si impurity concentrations. © 1991, The Electrochemical Society, Inc. All rights reserved.