Optical and structural properties of GaN epitaxial layers on LiAlO2 substrates and their correlation with basal-plane stacking faults

• PL, XRD, SEM were used for characterization of m-plane GaN layers grown on LiAlO2.
• A gradient of basal-plane stacking faults (BSF) density along the wafer was revealed.
• A correlation of in-plane strain εxx and εzz with the BSF density was observed.
• The role of anisotropic mosaicity in limitation of the BSF length was demonstrated.

The optical and structural properties of m-plane GaN layers grown by metal organic vapor phase epitaxy on LiAlO2 (100) substrates were investigated. Temperature-dependent and time-resolved photoluminescence (PL), X-ray diffraction and Raman scattering measurements were performed to analyze the correlation of the sample properties with the density of I1-type basal-plane stacking faults (BSFs). Electron channeling contrast imaging was used to reveal and calculate the density of BSFs reaching the surface of an m-plane GaN/LiAlO2 layer. It was shown that a local increase of BSF density in the investigated samples results in a rise of the total PL efficiency at low temperatures because of the localization of excitons at BSFs and, therefore, a suppression of their diffusion to nonradiative centers. Parameters of time decay and temperature quenching of the BSF-related PL band were determined. A correlation of both εxx and εzz strain components with the BSFs and crystal mosaicity was observed, and possible reasons of this correlation are discussed.