Characterization of free standing GaN grown by HVPE on a LiAlO2 substrate

A 230 µm thick free standing GaN layer has been grown on a LiAlO2 substrate by hydride vapor phase epitaxy, with the separation of the layer from the substrate occuring spontaneously during cooling down after growth. A strong green luminescence band is observed from the top surface, while from the bottom surface, strong blue and red bands are seen in photoluminescence (PL). The evolution of these luminescence bands with layer thickness was monitored by cross-sectional cathodoluminescence (CL). PL and CL measurements indicate that the defect structure changes with growing layer thickness. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)