Significance of a Nucleation Layer in Inhibiting Interfacial Pitting in InAs Films Grown by Two-Step MOVCD on (100) Inp Substrates

Abstract

AbstractIn this paper, we study the significance of a low temperature nucleation layer and its role in inhibiting interfacial pitting vapor deposition. Transmission electron microscopy and scanning electron microscopy studies show that severe interfacial pitting occurs for thin nucleation layers of average thicknesses of 200Å and 400Å. For these average nucleation layer thicknesses we have found that the InAs islands do not cover the entire substrate surface during the low temperature deposition. Hence, when the film is heated to a higher temperature for the growth of the remainder of the film severe pitting at the heterointerface is produced. The thermal etchpits are sources of threading dislocations, which propagate to the surface of the film. For thicker nucleation layers we observe no interfacial pitting. Our studies show that there is an optimum nucleation layer thickness for which high quality InAs films with reduced threading dislocation densities and relatively high electron mobilities are obtained. Both electrical and structural studies suggest that ∼ 800Å is an optimum thickness of the low temperature nucleation layer.