Structural and electrical characterization of InAs grown on GaAs substrates by molecular-beam epitaxy

Abstract

Epitaxial InAs:Sn is grown on semi-insulating GaAs substrates by molecular-beam epitaxy. The large lattice mismatch between these materials (∼7.1%) generates a high density of threading dislocations which propagate into the epitaxial film. Both plan-view and cross-sectional transmission electron microscopy techniques are used to investigate the generation and propagation of these dislocations. For films that exceed the critical thickness, the threading dislocation density is inversely proportional to the epilayer thickness. Epitaxial layers incorporating growth interrupts have lower overall defect densities, yet maintain defect reduction profiles similar to those observed in layers grown without the growth interrupt. Room-temperature mobilities for InAs:Sn epitaxial layers varied from 11 200 to 22 100 cm2/V s for epilayer thicknesses of 0.4 to 4.4 μm, respectively. The thickness dependence on the mobility is attributed to a multiplicity of factors including surface scattering, interfacial strain, surface accumulation, and the high interfacial dislocation density.