Compositional profile of heteroepitaxial InAs on GaAs substrates

The nature of the interface region between semiconducting heteroepitaxial layers and their substrates has been experimentally studied using Auger electron spectroscopy and energy dispersive X-ray analysis. InAs grown epitaxially on single-crystal semi-insulating GaAs was investigated since it has exhibited electrical properties superior to those of bulk InAs in spite of the considerable crystal lattice mismatch between InAs and GaAs.Findings indicate the existence of a graded composition (In_xGa_1-xAs) region of approximately 1500 Å thickness between the substrate and epilayer which is thought to play a major role in strain relief and, consequently, in determining the electrical characteristics of the resulting InAs epilayer.