Bismuth alloying in GaAs: a first-principles study

We present a theoretical study mainly devoted to the investigation of the bowing parameter in the GaAs_1–xBi_x alloy. Results reveal that the fundamental band gap for GaAs is close to 0.08 eV and it corresponds to −2.01 eV for GaBi. The addition of Bi to GaAs serves to make the lattice constant of the crystal larger than GaAs and distorts the valence band. This causes an intrinsic asymmetry between the carrier mobility. The band gap of GaAsBi alloy decreases with increasing Bi content. Moreover, the non-linear variation of the lattice parameter is clearly visible with upward bowing parameter, equal to −0.378 ± 0.16 Å. Compared with preceding works on the matter, the band gap versus composition is well fitted with a downward bowing parameter of 1.74 ± 0.51 eV. This shows that the direct band gap of this alloy covers a spectral region ranging from near infrared to infrared.