EFFECT OF CHLORIDE ETCHING ON GAAS EPITAXY USING TMG AND ASH3

A study has been made of the effect of in situ etching of (100) Cr-doped semi-insulating and Te-doped n + -GaAs substrates on epitaxial layers, grown by the reaction of trimethylgallium and arsine. It is shown that in situ etching enables the growth rate to be increased by a factor of two while retaining a specular surface. In addition, the Hall mobility is higher in epitaxial layers grown on in situ etched substrates than on unetched ones. Epitaxial films on both AsCl3 and HC1 gas-etched substrates had a room temperature mobility that decreased from ~6100 cm2/V-sec in 5.5 μm layers to ~5100 cm2/V-sec in 1 μm layers. However, for layers grown on substrates which were not in situ etched, the mobility decreased from ~5800 to ~3800 cm2/ V-sec for layer thicknesses from 5.5 to 1 μm, respectively. Further it is shown that the carrier concentration profile is more abrupt near the epitaxial layer/ Te-doped GaAs substrate interface when the substrates were in situ etched. Finally, experiments with chloride etching during growth were disappointing because it was not possible to obtain simultaneously good surface morphology, low carrier concentration, and high mobility for any given set of reactor conditions. © 1978, The Electrochemical Society, Inc. All rights reserved.