Nonrad: Computing Nonradiative Capture Coefficients from First Principles

TL;DR

This paper introduces Nonrad, a first-principles computational tool for accurately calculating nonradiative carrier capture rates in semiconductors, addressing previous approximation errors and improving predictive reliability.

Contribution

The paper presents the Nonrad code implementing a quantum-mechanical approach for nonradiative capture coefficients, including improved electron-phonon coupling evaluation and vibrational broadening treatment.

Findings

Implemented a new scheme for vibrational broadening that reduces errors.

Compared analytic and numerical methods for Sommerfeld parameter, validating accuracy.

Provided a first-principles method for more reliable defect recombination rate calculations.

Abstract

Point defects in semiconductor crystals provide a means for carriers to recombine nonradiatively. This recombination process impacts the performance of devices. We present the Nonrad code that implements the first-principles approach of Alkauskas et al. [Phys. Rev. B 90, 075202 (2014)] for the evaluation of nonradiative capture coefficients based on a quantum-mechanical description of the capture process. An approach for evaluating electron-phonon coupling within the projector augmented wave formalism is presented. We also show that the common procedure of replacing Dirac delta functions with Gaussians can introduce errors into the resulting capture rate, and implement an alternative scheme to properly account for vibrational broadening. Lastly, we assess the accuracy of using an analytic approximation to the Sommerfeld parameter by comparing with direct numerical evaluation.