Implementation of Spatio-Time-Resolved Cathodoluminescence Spectroscopy for Studying Local Carrier Dynamics in a Low Dislocation Density m-Plane In0.05Ga0.95N Epilayer Grown on a Freestanding GaN Substrate

Abstract

Spatio-time-resolved cathodoluminescence (STRCL) spectroscopy is implemented to assess the local carrier dynamics in a 70-nm-thick, very low threading dislocation (TD) density, pseudomorphic m-plane In0.05Ga0.95N epilayer grown on a freestanding GaN substrate by metalorganic vapor phase epitaxy. Although TDs or stacking faults are absent, sub-micrometer-wide zonary patterns parallel to the c-axis and 2-µm-long-axis figure-of-8 patterns parallel to the a-axis are clearly visualized in the monochromatic cathodoluminescence intensity images. Because the STRCL measurement reveals very little spatial variation of low-temperature radiative lifetime, the considerable peak energy variation is interpreted to originate from nonidentical In-incorporation efficiency for the growing surfaces exhibiting various miscut angles. The figure-of-8 patterns are ascribed to originate from the anisotropic, severe m-plane tilt mosaic along the a-axis of the GaN substrate, and the zonary patterns may originate from the m-plane tilt mosaic along the c-axis.