Radiation Damage and Point Defects in GaSb and InAs

Narrow gap semiconductors are suitable materials for the design of infrared sensors (IR), but they suffer from the formation of defects that can affect device performance. Density-Functional-Theory (DFT) can provide insights into changes in electronic structure due to defect formation. However, standard DFT methods predict GaSb and InAs to be metallic, while experiment shows them to be semiconducting. Our results, based on Hubbard U+V extensions to standard DFT, recover the semiconducting state with bandgaps of 0.82 eV and 0.30 eV, for GaSb and InAs, respectively, consistent with the extrapolated T=0 K corresponding bandgaps of 0.81 eV and 0.42 eV. For small simulation cells, the defect-induced electronic band dispersion is larger than the bandgap, hindering the analysis of whether electronic defect states reside in the bandgap or not. With increasing simulation cell size, and increasing defect-defect distances, this dispersion decreases, and for the experimentally observed Sb_Ga defect, we find that the electronic defect states reside in the bandgap. We will discuss the impact of these results for the operation and reliability of infrared sensors. *SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.