Transmission electron microscopy studies of the microstructure of Si layers grown on GaAs(001) under an excess As or Al flux

Abstract

Abstract Si layers with nominal thickness of 30–40 monolayers were grown at 400°C on GaAs(001)c(4 × 4) surfaces under an excess As or Al flux. Similar growth conditions are used by some workers to fabricate Si interlayers in metal/GaAs diodes and to modify the Schottky barrier. We investigated the microstructural changes caused by the expected large As or Al incorporation in the Si layers. We found that Si epitaxial layers grown under an As flux have a structure similar to that of control samples in which the Si layer was grown in the absence of any excess anion or cation flux. Surprisingly, the only microstructural modification induced by the excess As is a somewhat higher density of extended defects at the interface. Conversely, the use of an excess Al fiux during growth yields large microstructural modifications relative to the control samples. A relatively thick, highly disordered quaternary layer appears to form on most of the surface, while Ga islands are also observed, sometimes with the inclusion of A1 clusters.