Optical transitions in new semiconductor alloy GaAs1-xBi x with temperature-insensitive band gap

We performed photoreflectance (PR) spectroscopy in order to investigate fundamental band-edge transitions of GaAs_1-xBi _x alloys. GaBi-mole fractions of GaAs_1-xBi_x investigated in this study are 0, 0.005, 0.012 and 0.024. The PR spectra for the four samples exhibit Franz-Keldysh oscillations (FKO) above the band-gap energy due to the built-in electric field. The FKO signal enables us to evaluate the band-gap energy. We found that a small amount of the Bi content succeeds in producing a temperature-insensitive band gap. The reduced effective mass ratio between the heavy- and light-hole bands μ_hh/μ_lh was estimated by fast Fourier-transform analysis for the PR spectra. These results show that μ_hh/μ_lh is larger for higher Bi content