SCALE Effects of Electronic and Structural Properties of Point Defects on Indium Atimonide

Graduate student Marcos Calva of NMSU presented at the Vanderbilt Seminar Series.

Indium antimonide (InSb) is a group III‑V narrow‑gap semiconductor distinguished by exceptionally high electron mobility and a direct bandgap, making it a cornerstone material for photodiodes, lasers, and advanced nanoelectronic devices. Its relevance stems from the critical role that electronic and structural imperfections play in determining device performance, especially in infrared detection technologies. Understanding how point defects modify the intrinsic properties of InSb therefore underpins both fundamental research and practical engineering of high‑sensitivity detectors.
The presentation examines intrinsic point defects in InSb, focusing on antisite configurations (InSb​ and SbIn​) and vacancy species (VIn​ and VSb​). Density‑functional theory (DFT) calculations are performed with ultra‑soft pseudopotentials within the Quantum ESPRESSO framework, employing the PBE‑GGA exchange‑correlation functional. Standard DFT erroneously predicts a metallic ground state for InSb, prompting the adoption of a DFT + U + V Hubbard correction that restores the experimental bandgap (~0.235 eV at 0 K) by enforcing local and inter‑site Coulomb interactions. Systematic convergence tests determine optimal plane‑wave energy cutoffs (≈25 Ry) and charge‑density scaling factors, ensuring reliable total‑energy, force, and electronic‑structure predictions for defect‑containing supercells.