Resolving the mystery of the concentration-dependence of amphoteric dopant diffusion in III-V semiconductors

Abstract

Amphoteric dopants, such as silicon, exhibit a concentration-dependent diffusivity in III-V compounds characterized by a low to negligible diffusion at low dopant concentrations, which increases by orders of magnitude at high concentrations. The reason for this anomalous and non-intuitive diffusivity has largely remained a mystery. Leading models from literature, built to explain existing experimental results, make contradictory assumptions on the nature of the diffusing species, based only on thermodynamic considerations. In this work, we perform ab initio calculations to characterize the kinetics of dopant diffusion in III-V materials revealing how the nature of the primary diffusing species changes with concentration. We use these results to derive a new analytical model which fits historical, as well as more recent, experimental data on Si diffusion in GaAs and In0.57Ga0.43As. This work provides a fundamentals-based understanding of Si diffusion in III-V alloys as well as a new predictive analysis tool while showcasing a mutiscale approach of solving diffusion problems. We hope this work will help guide the design of the next generation of III-V based electronic and photonic devices.