Nonrad: Computing nonradiative capture coefficients from first principles

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. (2014) [8] 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.

半导体晶体中的点缺陷为载流子的非辐射复合提供了途径。此复合过程对器件的性能产生影响。本报告提出了Nonrad代码，该代码实现了Alkauskas等人（2014年）[8]提出的基于捕获过程量子力学描述的第一性原理方法，以评估非辐射捕获系数。本文还提出了一种在投影增强波形式中评估电子-声子耦合的方法。此外，我们指出，用高斯函数替换Dirac delta函数的常见做法可能会引入捕获率的误差，并实施了一种替代方案以正确考虑振动展宽。最后，我们通过将解析近似Sommerfeld参数与直接数值评估进行比较，评估了使用解析近似的方法的准确性。