Defects In GaAs Bulk Crystals and Multi-Layers Caused by In Diffusion

Abstract

The objective of this work was to study by transmission electron microscopy the lattice defects in GaAs bulk crystals and heterostructures formed by In diffusion. In such samples hints for the existence of superconductivity have been found. Indium was found to move more than 100 μm into bulk GaAs during lh annealing at 550ºC (such conditions are typical for molecular beam epitaxy growth on GaAs wafers). This rapid diffusion is accompanied by the creation of dislocation networks and metallic In droplets that show evidence for lattice strain. To study the interaction of In with the GaAs lattice, In/GaAs multi-layers were grown by MBE at about 450ºC on a GaAs buffer layer. The interfaces of these structures showed misfit dislocations at islands of InAs besides the presence of lattice strain. Both types of samples showed microwave absorption signals typical for superconductivity. The most likely superconductive phases are small metastable inclusions, probably consisting of amorphous Ga or In.