First principles calculations of carrier dynamics of screw dislocation

Abstract

Nonradiative carrier recombination (NCR) in semiconductor is a fundamental process determining the efficiencies of many semiconductor devices. There is a longstanding debate on which line defect is an efficient NCR center, especially in third generation semiconductor. Here we developed a systematic method to calculate the electronic structure and NCR dynamics of screw dislocation. We studied the full-core screw dislocation of GaN with atomic structure taken from TEM images, and found that there are inside band gap dislocation states. Under n-type GaN condition, these band gap states will become occupied, making the core negatively charged, and inducing a potential well, which will attract minority hole carriers. Large-scale NAMD simulation shows that the holes can easily jump across a small band gap in the dislocation state band structure and hence will be annihilated with the electron nonradiatively, which agrees with the experimental observation of the photoluminescence dark spot on each dislocation.