Optical and Electronic Properties of ErAs:GaAs$_{1-x}$Bi$_x$

We measured the optical absorption of ErAs:GaAs$_{1-x}$Bi$_x$ ($x = 5.3\%$), grown by molecular beam epitaxy, using Fourier Transform Infrared (FTIR) transmission spectroscopy over a spectral range from 50 um (0.02 eV) to 500 nm (2.48 eV) at room temperature. The band structure of GaAs$_{1-x}$Bi$_x$ ($x = 1.56, 5.3\%$), were calculated with Density functional theory (DFT) using QUANTUM ESPRESSO. The band structure due to Bi incorporation in GaAs from these models are also used to investigate ultrafast dynamics in infrared pump-terahertz probe experiments.