Understanding band alignments in semiconductor heterostructures: Composition dependence and type-I-type-II transition of natural band offsets in nonpolar zinc-blende AlxGa1-xN/AlyGa1-yN composites

作者：Landmann M^*; Rauls E; Schmidt W G

来源：Physical Review B, 2017, 95(15): 155310.

DOI：10.1103/PhysRevB.95.155310

The composition dependence of the natural band alignment at nonpolar AlxGa1-xN/AlyGa1-yN heterojunctions is investigated via hybrid functional based density functional theory. Accurate band-gap data are provided using Heyd-Scuseria-Ernzerhof (HSE) type hybrid functionals with a composition dependent exact-exchange contribution. The unstrained band alignment between zincblende (zb) AlxGa1-xN semiconductor alloys is studied within the entire ternary composition range utilizing the Branch-point technique to align the energy levels related to the bulklike direct Gamma(v) -> Gamma(c) and indirect, pseudodirect, respectively, Gamma(v) -> X-c type transitions in zb-AlxGa1-xN. While the zb-GaN/AlxGa1-xN band edges consistently show a type-I alignment, the relative position of fundamental band edges changes to a type-II alignment in the Al-rich composition ranges of zb-AlxGa1-xN/AlN and zb-AlxGa1-xN/AlyGa1-yN systems. The presence of a direct-indirect band-gap transition at x(c) = 0.63 in zb-AlxGa1-xN semiconductor alloys gives rise to a notably different composition dependence of band discontinuities in the direct and indirect energy-gap ranges. Below the critical direct-indirect Al/Gacrossover concentration, the band offsets show a close to linear dependence on the alloy composition. In contrast, notable bowing characteristics of all band discontinuities are observed above the critical crossover composition.

• 出版日期2017-4-12