Lateral Growth Process of GaAs over Tungsten Gratings by Metalorganic Chemical Vapor Deposition

Abstract

Lateral epitaxial growth of GaAs over tungsten gratings with 5 t~m wide lines and spaces on (001) GaAs substrates i performed using metalorganic chemical vapor deposition. A study is made of the dependence of facet shapes and growth rates of the overgrown layers on grating direction, growth temperature, and arsine (AsH:~) and trimethylgallium (TMG) flow rates. From the perspective of crystallography = all the facets observed in the overgrown layers were found to be classified into four individual groups: {110}, {lll}As, {ll2}As, and {ll3}Ga faces. The GaAs opening direction on the (001) substrate surface is found to be the most essential parameter for determining the crystallographic planes of the fac-ets. Other important controlling parameters for the facet formation are the growth temperature and partial pressure of ASH:, The partial pressure of TMG has no influence on the faceting rowth. On the other hand, the overall growth rate of the overgrown layer is limited only by the TMG flow rate. These results can be qualitatively explained by the Langmuir-Ridea] model. Lateral epitaxial growth over oxide or metal mask films formed on crystal substrates has recently devel-oped into an attractive technique for fabricating such new devices as permeable base transistors (PBT's) (1-3) and