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

## TL;DR

This study compares how two growth methods affect the radiation resistance of InSb semiconductor layers, revealing how each responds to gamma irradiation.

## Contribution

The paper introduces a novel comparative analysis of MOCVD and MBE InSb epilayers under gamma irradiation, revealing atomic-level mechanisms of defect evolution.

## Key findings

- MOCVD-grown InSb shows higher initial quality but degrades more under gamma irradiation.
- MBE-grown InSb exhibits defect saturation and better survivability at high radiation doses.
- Radiation-induced Sb–Sb bonds and interface instability are key factors in electronic degradation.

## Abstract

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.