Understanding Bond-Selective Damage Mechanisms for Radiation-Tolerant III-V APD Heterointerface Design: A Coupled AIMD-Monte Carlo Study

Abstract

Developing radiation-tolerant InGaAs-based photodetectors is essential for space applications. Displacement damage is often characterized by defect formation and energy-loss metrics, yet the bond-selective atomistic mechanisms linking it to electronic degradation at III-V heterointerfaces remain unclear. This study combines ab initio molecular dynamics with Monte Carlo simulations to investigate radiation damage in the InGaAsP/InGaAs heterointerface. Threshold displacement energies (TDEs) of primary knock-on atoms (PKAs) were determined along [001], [010], [110], and [111] relative to the (001) interface. Cation TDEs on the InGaAs side (In: 14-16 eV; Ga: 10-13 eV) exceed anion TDEs on the InGaAsP side (As and P: 9-12 eV), reflecting longer In-As bonds and resilient Ga-As bonding. Anion PKAs accommodate damage through local distortion and Frenkel-pair formation, whereas cation PKAs redistribute it through antisite exchange and replacement sequences; formation energies span 2.80-7.45 eV. Radial distribution analysis reveals the bond-selective response: In-P reconstruction near the second coordination shell and Ga-As sensitivity to angular deformation, which narrow the band gap and induce band-edge tailing. Nuclear stopping dominates energy loss, and the stepwise increase in projected range (6.2-8.2 Å) between 25 and 75 eV broadens the ring-like damage profiles; correspondingly, the cascade localization index decreases from 0.908 to 0.649, marking a transition from localized bond-level damage to distributed cascade disorder with gap closure at 75 eV. These results rely on PBE-GGA, four directions sampled at single sites, and a 288-atom supercell, and therefore indicate relative trends rather than averaged values. The findings establish a bond-to-cascade mechanism for designing radiation-tolerant III-V APD heterointerfaces.