Replica observation by transmission electron microscopy of GaAs surface grown on vicinal Si (001)

Abstract

Over the past several years, heteroepitaxy of GaAs on Si substrates has received strong interest because of its potential for monolithic integration of GaAs optical devices with Si integrated circuit technology. For heteroepitaxy of GaAs on Si substrate, Si(001) substrates oriented toward [110] by a few degrees (1) are used, therefore the GaAs epitaxial layer is expected to have a stepped surface. In this study, we characterized the GaAs surface, grown on vicinal Si(001 ) substrates, by replica observation using transmission electron microscopy (TEM).The Si substrates were oriented 2 degrees off towards [110] and their surface was expected to have a regular array of [110] steps, 8 nm apart. A two-step growth process (1) was employed to grow GaAs on Si(001) by metalorganic chemical vapor deposition (MOCVD). The Ga source was trimetyl gallium (TMG) and As source was AsH3. Following 10 minutes of 1000°C heat treatment in a H2, gas flow to remove the native oxide, 20 nm GaAs buffer layers were grown at 450°C. They were then heated to a growth temperature of 650°C to grow the GaAs epitaxial layers an additional 3 μm.