Temperature-dependent transport properties of InAs films grown on lattice-mismatched GaP

Abstract

Hall effect and electrical resistivity measurements were carried out on undoped InAs thin films grown by molecular-beam epitaxy directly on (001) GaP substrates. The large lattice mismatch between these two compounds results in a high density array of misfit dislocations at the heterointerface and threading dislocations in the InAs epilayer. The threading dislocation density varies with epilayer thickness, with the largest proportion being present near the heterointerface. This leads to variation of both the carrier concentration and electron mobility with thickness. Consequently, a multilayer analysis was used to interpret the transport data. This analysis yields a temperature-independent carrier concentration, which indicates degenerate donor levels in this narrow band-gap material. Room temperature mobilities in excess of 10 000 cm2/V s were obtained for thick InAs layers despite dislocation densities of 1010 cm−2. The relative insensitivity of the mobility to temperature suggests that temperature-independent scattering dominates over ionized impurity/defect and phonon scattering.