Optical transitions in new semiconductor alloy GaAs/sub 1-x/Bi/sub x/ with temperature-insensitive band gap

We performed photoreflectance (PR) spectroscopy in order to investigate fundamental band-edge transitions of GaAs/sub 1-x/Bi/sub x/ alloys. GaBi-mole fractions of GaAs/sub 1-x/Bi/sub 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 /spl mu//sub hh///spl mu//sub lh/ was estimated by fast Fourier-transform analysis for the PR spectra. These results show that /spl mu//sub hh///spl mu//sub lh/ is larger for higher Bi content.