Radiation Damage and Point Defects in InSb

Small gap semiconductors such as InSb are materials suitable for infrared (IR) detectors. However, defects caused by radiation can affect device performance due to defect related electronic states in the bandgap. We use Density-Functional-Theory (DFT) to predict the electronic, magnetic, and optical properties of experimentally observed point defects in InSb. However, standard DFT methods predict InSb to be metallic, in contrast to its experimentally well-established semiconducting behavior. Our results, based on Hubbard U+V extensions of standard DFT, show the opening of a bandgap of 0.36 eV consistent with the extrapolated T = 0 K experimental bandgap of 0.24 eV. For small simulation cells, the electronic dispersion is larger than the narrow bandgap, hindering the determination of electronic defect states residing in the bandgap. Increasing the size of the simulation cell decreases electronic dispersion and shows that some defects, such as Sb_In, have electronic states in the bandgap of the host material. These results show that some defects provide additional recombination pathways that must be understood for the evaluation of IR detector readiness and reliability. *SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.