The electronic band structure of GaBiAs/GaAs layers: Influence of strain and band anti-crossing

Abstract

Electronic structure of C2N2X (X=O, NH, CH2): Wide band gap semiconductors J. Appl. Phys. 112, 013537 (2012) In-plane mapping of buried InGaAs quantum rings and hybridization effects on the electronic structure J. Appl. Phys. 112, 014319 (2012) Incorporation, valence state, and electronic structure of Mn and Cr in bulk single crystal β-Ga2O3 J. Appl. Phys. 111, 123716 (2012) Determination of conduction band offset between strained CdSe and ZnSe layers using deep level transient spectroscopy Appl. Phys. Lett. 100, 252110 (2012) Electronic structure and linear magnetoresistance of the gapless topological insulator PtLuSb Appl. Phys. Lett. 100, 252109 (2012) Additional information on J. Appl. Phys. The GaBi x As 1Àx 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 E g and spin-orbit splitting energy D o vary relative to one another as a function of Bi content, since in this alloy it becomes possible for D o to exceed E g 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 GaBi x As 1Àx (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 E g , together with an increase in D o , 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 6 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 (61) 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 E g and D o of free standing GaBiAs; we find that D o indeed does come into resonance with E g at $10.5 6 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. V C 2012 American Institute of Physics. [http://dx

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

“…In addition, photoreflectance measurements show that the energy separation, SO , between the spin-split-off valence band and the valence band edge also increases rapidly with Bi composition. 9 This then leads to the situation in GaBi x As 1−x where the spin-orbit-splitting energy can exceed the energy gap SO E g for x 9%. This is of significant potential benefit for telecommunication lasers, because it could enable the suppression of the Auger recombination losses which dominate the threshold characteristics of GaInAsP and AlGaInAs lasers.…”

“…[16][17][18] The theoretical analysis was undertaken using the sp 3 s * tight-binding Hamiltonian which we have developed for GaBiAs 2 to investigate the electronic structure of large randomly disordered supercells. The electronic structure is studied experimentally by photomodulated reflectance (PR) spectroscopy, 9 which is considered to be an excellent technique due to its sensitivity to critical point transitions in the band structure. 19 Further details of the experimental procedure are described by Batool et al,9 while the sample details can be found in the work of Lu et al 16,17 Three sets of features are found in the PR spectra, associated with transitions between the conduction band minimum at and valence states which respectively include host matrix heavy-hole (HH), light-hole (LH), and spin-split-off (SO) character.…”

“…The electronic structure is studied experimentally by photomodulated reflectance (PR) spectroscopy, 9 which is considered to be an excellent technique due to its sensitivity to critical point transitions in the band structure. 19 Further details of the experimental procedure are described by Batool et al,9 while the sample details can be found in the work of Lu et al 16,17 Three sets of features are found in the PR spectra, associated with transitions between the conduction band minimum at and valence states which respectively include host matrix heavy-hole (HH), light-hole (LH), and spin-split-off (SO) character. Our calculations provide a detailed understanding of the broadening observed in the PR measurements for each of these features due to the presence not just of isolated Bi atoms but also of pair and cluster states.…”

Valence band splitting in bulk dilute bismides

“…In addition, a VBS of bulk GaAs 1−x Bi x has been observed in tight-binding calculations by Usman et al 9 even though the authors do not further comment on it. They find an increase of the splitting in the case of compressive strain 10 which slightly underestimates the splitting reported by Batool et al 6 .To systematically study Bi induced VBS, we use density functional theory (DFT) for the calculation of the band structures of dilute bismide semiconductors. Remarkably, our results show that a large VBS in the range of tens to more than hundred meV exists for bulk systems without any external strain.…”

“…A wellknown example is the valence band splitting (VBS) in III-V semiconductors caused by strain due to lattice-mismatched growth 5 . Experimentally, VBS was observed for GaAs 1−x Bi x layers grown lattice-mismatched on GaAs substrates 1,6,7 . To analyze the observations, Batool et al 6 extracted the shear deformation potential for a Bi content up to x = 10.4 %.…”