Bowing of the band gap and spin-orbit splitting energy in BGaAs

BGaAs layers with the boron concentration up to 17.7% have been grown by molecular beam epitaxy on GaAs and GaP substrates and studied by photoreflectance (PR) spectroscopy. The direct optical transitions between the valence band (heavy hole, light hole, and the spin–orbit split-off band) and the conduction band have been observed in PR spectra. The bowing parameter for the band gap and the spin–orbit splitting has been determined from PR studies to be 3.6 ± 0.2 and 0.2 ± 0.1 eV, respectively. These values are very close to those determined using state-of-the-art first principle density functional methods (bdir = 3.5 ± 0.1 eV and bSO = 0.06 ± 0.02 eV). In addition, the indirect band gap has been examined theoretically and the bowing parameter has been determined to be 2.3 ± 0. eV, with the crossing between the direct and indirect gap in BGaAs at ∼12% B.