Simplified kinetic Monte Carlo modeling of CdTe/GaAs (100) heteroepitaxy: Investigating defect generation and critical thickness

This study employs a phenomenological kinetic Monte Carlo method, coupled with the Bending Restricted Model as a simplification of the Valence Force Field model, to investigate atomic-scale mechanisms of heteroepitaxial growth of a Te monolayer on GaAs (100) and point defect occurrence using the concept of “soft” substrates. Our results demonstrate that defect formation is negligible for a rigid GaAs (with a real substrate elasticity: ks=1.1eV). We identify a critical threshold elasticity constant, ksth≈0.12eV, above which defect creation mechanisms are activated. These defects undergo self-annihilation, often followed by reappearance at a neighboring site via bond rupture. This defect activity preferentially nucleates and propagates in high-stress regions, ultimately leading to the formation of extended defects that influence the material's macroscopic mechanical properties. Based on these findings, we propose a novel phenomenological relationship for the critical layer thickness (hc): hc=ks/ksth, where ks is the real substrate rigidity. This formula yields an estimated critical thickness of approximately nine monolayers for the CdTe/GaAs system. This result qualitatively aligns with existing theoretical predictions and is consistent with experimental observations for systems with high lattice mismatches. This work provides essential atomic-scale understanding of defect evolution and offers a robust predictive tool for heterostructure engineering.