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

Usman, M., Broderick, C. A., Batool, Z., Hild, K., Hosea, T. J. C., Sweeney, S. J. and O'Reilly, E. P. (2013) Impact of alloy disorder on the band structure of compressively strained GaBixAs1-x. Physical Review B, 87(11), 115104. (doi: 10.1103/PhysRevB.87.115104)

Abstract

The incorporation of bismuth (Bi) in GaAs results in a large reduction of the band gap energy (Eg) accompanied with a large increase in the spin-orbit splitting energy (△SO), leading to the condition that △SO>Eg, 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 GaBixAs1−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 Eg 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 band-anticrossing 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 GaBixAs1−x. Our calculations support a type-I band alignment at the GaBixAs1−x/GaAs interface, consistent with recent experimental findings.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Hild, Dr Konstanze and Sweeney, Professor Stephen
• Authors: Usman, M., Broderick, C. A., Batool, Z., Hild, K., Hosea, T. J. C., Sweeney, S. J., and O'Reilly, E. P.
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Journal Name: Physical Review B
• Publisher: American Physical Society
• ISSN: 1098-0121
• ISSN (Online): 1550-235X

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