Electronic band structure of GaBiAs/GaAs layers: influence of strain and band anti-crossing, Z. Batool, K. Hild, T. J. C. Hosea, X. Lu, T. Tiedje, S. J. Sweeney, J. Appl. Phys. 111, 113108 (2012)

The GaAs1-xBix bismide III-V semiconductor system remains a relatively underexplored alloy particularly with rEgards to its detailed electronic band structure. Of particular importance to understanding the physics of this system is how the bandgap energy Eg and spin-orbit splitting energy ΔO vary relative to one another as a function of Bi content, since in this alloy it becomes possible for ΔO to exceed Eg for higher Bi fractions, which occurrence would have important implications for minimising non-radiative Auger recombination losses in such structures. However, this situation had not so far been realised in this system. Here, we study a set of epitaxial layers of GaAs1-xBix (2.3% ≤ x ≤ 10.4%), of thickness 30-40 nm, grown compressively strained onto GaAs (100) substrates. Using room temperature photomodulated reflectance, we observe a reduction in Eg , together with an increase in ΔO, with increasing Bi content. In these strained samples, it is found that the transition energy between the conduction and heavy-hole valence band edges is equal with that between the heavy-hole and spin-orbit split-off valence band edges at ∼9.0 +/- 0.2% Bi. Furthermore, we observe that the strained valence band heavy-hole/light-hole splitting increases with Bi fraction at a rate of ∼15 (+/-1) meV/Bi%, from which we are able to deduce the shear deformation potential. By application of an iterative strain theory, we decouple the strain effects from our experimental measurements and deduce Eg and ΔO of free standing GaBiAs; we find that ΔO indeed does come into resonance with Eg at ∼10.5 +/- 0.2% Bi. We also conclude that the conduction/valence band alignment of dilute-Bi GaBiAs on GaAs is most likely to be type-I.