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The authors report on midinfrared photoreflectance measurements of the band gap ͑E 0 ͒ and spin-orbit splitting energies ͑⌬ 0 ͒ in InAs-rich InAsSb and GaInAsPSb samples for varying antimony contents ഛ22.5%. The E 0 behavior as a function of Sb content is consistent with the literature value bowing parameter of ϳ670 meV. However, ⌬ 0 does not exhibit the positive bowing of +1170 meV quoted in the literature: rather, a best fit to their data tentatively suggests a negative bowing of −225 meV. This result is likely to have strong impact due to the importance of the ⌬ 0 parameter in governing InAsSb-based device performance. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2728752͔ Recent interest in developing midinfrared ͑MIR, 2-5 m͒ light emitters and detectors has been driven by the wide range of potential applications in this spectral region. 1As a result of high Auger recombination coefficients, MIR semiconductors exhibit low quantum efficiencies and devices often have to operate below room temperature.2 The Auger recombination rates are sensitive to the fundamental band gap energy E 0 and ͓in the case of the conduction, heavy-hole, spin split-off hole, heavy-hole ͑CHSH͒ process͔ the spinorbit splitting energy ⌬ 0 .3 Therefore, in order to evaluate losses by these nonradiative recombination paths, a good knowledge of both E 0 and ⌬ 0 is essential.The InAs 1−x Sb x alloy plays a particularly important role in many MIR devices. 2,4,5 As a ternary alloy it is possible to define the compositional dependence of a parameter T ͑such as E 0 or ⌬ 0 ͒ using T = xB 1 + ͑1−x͒B 2 − x͑1−x͒C, where B 1 is the binary end-point InSb value, B 2 the InAs value, and C a bowing parameter which describes any deviation from the virtual crystal approximation. 6 A range of studies of E 0 in InAs 1−x Sb x indicates that C lies between 570-690 meV [7][8][9] and the review of Vurgaftman et al. recommends using C͑E 0 ͒ = + 670 meV. 10

Room-temperature electroluminescence is reported from InAsSb multiple-quantum-well light-emitting diodes. The diodes exhibited emission in the mid-infrared peaking near 4 m. The spectral dependence on injection current at 4 K was investigated and two transitions were identified, centered at 4.05 and 3.50 m, which are associated with the eigenstates of the confined holes inside the quantum well. The use of an Sb predeposition and As flux surface exposure during epitaxial growth was observed to have a major effect on the electroluminescence output.

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