Cathodoluminescence characterization of GaN thick films grown by using theHVPE method

Thick (> 200 mum) GaN films grown by hydride vapor-phase epitaxy (HVPE) wer e examined. High-quality films were examined by field emission scanning ele ctron microscopy (FE-SEM), cathodoluminescence (CL) spectroscopy, and imagi ng. We carried out spatially resolved studies of film cross-sections and th e 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 direct ly observe a region, about 20-mum thick, containing columnar structures.