The influence of implantation conditions on dopant activation in Al-implanted 4H-SiC: A MD study applying an Al potential fitted to DFT barriers

TL;DR

This study uses molecular dynamics simulations with a DFT-fitted Al potential to explore how implantation conditions affect defect evolution and dopant activation in Al-implanted 4H-SiC, revealing temperature and dose-dependent behaviors.

Contribution

It introduces a new MD simulation approach with a DFT-fitted Al potential to analyze defect dynamics and dopant activation in 4H-SiC during implantation and annealing.

Findings

Higher implantation temperature reduces Frenkel-pair production.

At high doses, higher temperature leads to larger, more stable interstitial clusters.

Two regimes of dopant behavior are identified around the Al solubility limit.

Abstract

We present molecular dynamics simulations of shallow Al implantation in 4H-SiC to clarify how implantation temperature and dose control defect evolution and dopant activation during early annealing. Using the Gao-Weber potential together with a reparameterized Morse Al-SiC interaction fitted to DFT migration and kick-in/out barriers, we find that higher implantation temperature reduces Frenkel-pair production and suppresses extended amorphous pockets. Yet at high doses (>1e20 cm^-3), annealing shows non-monotonic behavior: samples implanted at 900 K form larger, more stable interstitial clusters than those implanted at 500 K. These clusters trap Al and lower substitutional incorporation. Within MD-accessible times, the fraction of lattice-site Al is therefore higher after 500 K implantation despite better as-implanted crystallinity at 900 K. After annealing, two regimes emerge around the Al solubility limit: a low-dose regime dominated by isolated point defects and small complexes, and a high-dose regime with clustering and planar-defect formation that is strongly temperature dependent. The results explain the experimentally observed activation window (500-900 K) and indicate a kinetic route in which controlled nanoscale amorphization improves activation through regrowth-assisted incorporation while limiting extended defects. We also identify a new Al diffusion path and a carbon-antisite kick-out activation mechanism, both confirmed by DFT-NEB.