Experimental and Theoretical Study of Defect Evolution in InSb Epilayers under Gamma Irradiation: A Comparative Analysis of MOCVD vs MBE Growth Methods.

The operational requirements of high-radiation and extraterrestrial environments highlight the need to evaluate narrow-bandgap semiconductors that remain unexplored under such conditions, among them Indium Antimonide (InSb). As a material system, InSb offers unparalleled electron mobility and a massive g-factor, making it indispensable for next-generation infrared detection, Hall sensing, and topological quantum computing architectures. However, the practical realization of these devices is frequently hindered by the necessity of heteroepitaxial growth on lattice-mismatched substrates, typically Gallium Arsenide (GaAs), which introduces a complex landscape of threading dislocations and interfacial defects. This report presents an exhaustive, multimodal investigation into the radiation hardness of InSb epilayers, specifically contrasting the microstructural evolution of films grown via Metal-Organic Chemical Vapor Deposition (MOCVD) against those synthesized by Molecular Beam Epitaxy (MBE). Utilizing an experimental framework that integrates Electron Paramagnetic Resonance (EPR), Raman spectroscopy, High-Resolution Scanning Transmission Electron Microscopy (HR-STEM), and ab initio Density Functional Theory (DFT), this study elucidates the mechanistic divergence in radiation response between the two growth methodologies. The data reveal a critical, counterintuitive trade-off: the MOCVD-grown material, despite exhibiting superior initial crystalline quality driven by a zinc-doped seed layer that passivates interfacial traps, demonstrates a heightened susceptibility to electronic degradation and stoichiometry violation under high-fluence Gamma (γ) irradiation. In contrast, the MBE-grown material, initially marred by a higher density of dislocations, exhibits a complex "survivability" mode at elevated doses, characterized by defect saturation. This report details the atomic-level physics driving these behaviors, including the radiation-induced formation of homopolar Sb-Sb bonds, the symmetry-breaking anisotropy of the g-factor, and the thermodynamic instability of dopant-passivated interfaces under nonequilibrium conditions. Furthermore, these findings can be used as actionable engineering guidelines for Radiation Hardness Assurance (RHA), proposing novel nondestructive spectroscopic metrics for the qualification of semiconductors destined for space and nuclear applications.