Cathodoluminescence Characterization of GaN Thick Films Grown by Using the HVPE Method

Abstract

Thick (> 200 mum) GaN films grown by hydride vapor-phase epitaxy (HVPE) were examined. High-quality films were examined by field emission scanning electron microscopy (FE-SEM), cathodoluminescence (CL) spectroscopy, and imaging. We carried out spatially resolved studies of film cross-sections and the interface side of the GaN films/sapphire as well as the top surfaces. The top surfaces of the films showed narrow band-edge emission lines while the cathodoluminescence spectra near the interface were broad and extended to energies above the band gap. Close to the interface, we were able to directly observe a region, about 20-mum thick, containing columnar structures.