Composition dependence of band alignments in GaxIn1−xAsySb1−y heterojunctions lattice matched to GaSb and InAs

Abstract

A theoretical model utilizing a universal tight binding method and a correlated function expansion technique is presented to calculate the valence band maximum (VBM) and the conduction band minimum (CBM) of the binary (GaAs, InAS, GaSb, and InSb) and quaternary alloy GaxIn1−xAsySb1−y systems. By organizing the relative positions of the VBM and CBM between semiconductors, the band alignments and band types in the heterojunctions are determined. A straddling (type-I) band alignment in InAs/GaAs, InSb/GaAs, and GaSb/InSb, staggered (type-II) band alignment in GaSb/GaAs, and broken (type-III) band alignment in InSb/InAs and InAs/GaSb are found respectively. In addition, the compositional variations of VBM, CBM, valence band offset, conduction band offset, and band type for the alloy GaxIn1−xAsySb1−y lattice matched on GaSb and InAs are obtained as increasing the composition x. A pronounced upward bowing for the VBM and a very slight upward bowing (almost linear) for CBM are found, respectively. By controlling the compositions (x, y), band type transitions occur. The GaxIn1−xAsySb1−y heterojunctions lattice matched to GaSb changes their band types from type-III at x∼0→ to type-II at x = 0.07, and → to type-I at x = 0.38. In contrast, the GaxIn1−xAsySb1−y heterojunctions lattice matched to InAs changes their band types from type-II x∼0→ to type-III at x = 0.32. Reasonable agreement is obtained between our theoretical results and existing experimental data.