Impact of alloy disorder on the band structure of compressively strained GaBixAs1−x

Abstract

The incorporation of bismuth (Bi) in GaAs results in a large reduction of the band gap energy (E g ) accompanied with a large increase in the spin-orbit splitting energy ( SO ), leading to the condition that SO > E g , which is anticipated to reduce hot-hole producing Auger recombination losses whereby the energy and momentum of a recombining electron-hole pair are given to a second hole which is excited into the spin-orbit band. We theoretically investigate the electronic structure of experimentally grown GaBi x As 1−x samples on (100) GaAs substrates by directly comparing our data with room temperature photomodulated reflectance (PR) measurements. Our atomistic theoretical calculations, in agreement with the PR measurements, confirm that E g is equal to SO for x ≈ 9%. We then theoretically probe the inhomogeneous broadening of the interband transition energies as a function of the alloy disorder. The broadening associated with spin-split-off transitions arises from conventional alloy effects, while the behavior of the heavy-hole transitions can be well described using a valence bandanticrossing model. We show that for the samples containing 8.5% and 10.4% Bi the difficulty in identifying a clear light-hole-related transition energy from the measured PR data is due to the significant broadening of the host matrix light-hole states as a result of the presence of a large number of Bi resonant states in the same energy range and disorder in the alloy. We further provide quantitative estimates of the impact of supercell size and the assumed random distribution of Bi atoms on the interband transition energies in GaBi x As 1−x . Our calculations support a type-I band alignment at the GaBi x As 1−x /GaAs interface, consistent with recent experimental findings.

Novel Dilute Bismide, Epitaxy, Physical Properties and Device Application

“…A brief summary of the practical usage in Bi-containing III-V systems is given in Table 1. [68,69] k·p Model GaAs 1−x Bi x [58,70] GaBi x As 1−x /GaAs [63] InGaNAs [71] InGaAs 1−x Bi x [72] 2.1.…”

“…Usman et al [69] have investigated alloy disorder effects on the electronic structure of GaAsBi by comparing atomistic TB results with RT PR measurements. The disorder effects have a significant influence for low Bi compositions (2.3% and 4.5%) even in large supercells.…”

Highly mismatched III–V semiconductor alloys applied in multiple quantum well photovoltaics

“…By comparing these calculations to experiment we found the broadening linewidth of 25 meV can well describe broad band edge features in GaBiAs alloys to the impact of Bi-induced alloy disorder [17]; (v) increasing the Bi composition will not affect the magnitude of IQE but shift the IQE towards to the longer wavelength.…”

Growth of GaAsBi/GaAs Multi Quantum Wells on (100) GaAs Substrates by Molecular Beam Epitaxy

“…The band configuration of GaAsBi/GaAs is highly controversial. Tight binding band calculation of GaAsBi based on photoreflectance result suggests that GaAsBi/GaAs has the type I band configuration [20,21]. Very short decay time (70 ps) obtained by time resolved PL for a single 7.5-nm-thick GaAsBi QW at RT implies that it may have the type I band configuration.…”