Origin of Ga vacancy-related YL center in n-type GaN: A first-principles study

Abstract

The widely existed yellow luminescence (YL) in n-type GaN is attributed to Ga vacancy-related point defects. However, the nature of Ga vacancy-related YL centers, especially the identification of defect types, is still unclear. Based on first-principles calculations, we systematically investigated the defect formation energies, “0/+“-related optical transition processes and the hole non-radiative trapping of VGa-ON, VGa-VN, VGa-3H and VGa-ON-2H defects in n-type GaN. By static coupling method, the calculated capture cross-sections of VGa-ON and VGa-VN at 300 K are 3.52 × 10−14 cm2 and 6.22 × 10−14 cm2, respectively, which are in good agreement with the hole capture cross-sections of YL center measured by deep-level transient spectroscopy (DLTS) experimentally. While the calculated capture cross-section of 2.46 × 10−13 cm2 for VGa-ON-2H is three times of the maximum experimental data, and the value 1.02 × 10−12 cm2 for VGa-3H is 1–2 orders of magnitude larger than the experimental results. The calculated hole capture cross-sections of these defects centers are quite different, but the transitions between 0 and + charge states of the above defects are all consistent with the experimental YL emission process. This work provides the correlation between the VGa-related defects and the YL center in n-type GaN, bringing essential information to a long-standing controversy.