InGaBiAs/InP semiconductors for mid-infrared applications: Dependence of bandgap and spin-orbit splitting on temperature and bismuth content

Replacing small amounts of As with Bi in InGaBiAs/InP induces large decreases and increases in the bandgap, E_g, and spin-orbit splitting, Δ_SO, respectively. The possibility of achieving Δ_SO>;E_g and a reduced temperature (T) dependence for E_g are significant for suppressing recombination losses and improving performance in mid-infrared photonic devices. We measure E_g(x, T) and Δ_SO(x, T) in In_0.53Ga_0.47Bi_xAs_1-x/InP samples for 0≤x≤0.032 by optical spectroscopy. While we find no clear evidence of a decreased dE_g/dT (≈0.33±0.07meV/K in all samples) we find Δ_SO>;E_g for x>;3.3-4.3%. The predictions of a valence band anti-crossing model agree well with the measurements.