Tuning linear and nonlinear optical properties of wurtzite GaN by c-axial stress

TL;DR

This study uses density functional theory to show that applying tensile c-axial stress to wurtzite GaN enhances its linear and nonlinear optical properties, improving efficiency and electron mobility.

Contribution

It demonstrates how tensile c-axial strain can be used to tune and improve the optical and electrical properties of wurtzite GaN.

Findings

Tensile c-axial strain increases linear optical efficiency.

Strain enhances second-order nonlinear optical susceptibilities.

Stress reduces polarization, improving optical responses.

Abstract

We study the linear and nonlinear optical properties of wurtzite GaN under c-axial stress field, using density functional theory calculations. The fully structural optimization at each c-axial strain was performed. The calculated dielectric functions show that tensile c-axial strain effectively improves the linear optical efficiency, especially for the band-edge transitions, and significantly increase the mobility of electrons in the conduction band. Second-order nonlinear optical susceptibilities show that the tensile c-axial strain will enhance the zero- and low-frequency nonlinear responses of GaN. The enhancement of the nonlinear optical property is explained by the reduction of the polarization of wurtzite GaN under tensile c-axial strains. Based on these findings, we propose a method for improving the electrical and optical properties of the crystal through imposing appropriate stress on the high symmetry crystalline directions.