COMPARISON OF HYDRIDE VAPOR-PHASE EPITAXY OF GAN LAYERS ON CUBIC GAN/(100)GAAS AND HEXAGONAL GAN/(111)GAAS SUBSTRATES

GaN layers were homoepitaxially grown by hydride vapor phase epitaxy (HVPE) on cubic GaN/(100)GaAs and hexagonal GaN/(111)GaAs substrates, and the growth conditions and crystalling qualities were compared between both cases. HVPE GaN layers were epitaxially grown on hexagonal GaN/(111)GaAs substrates when the substrate temperature was below 700 degrees C, whereas on cubic GaN/(100)GaAs substrates, they were epitaxially grown only at substrate temperatures above 800 degrees C. Two-step growth was necessary for higher-quality hexagonal GaN epilayers to be grown at 900 degrees C. The growth rate of HVPE GaN epilayers on hexagonal GaN/(111)GaAs substrates was about 2.5 times higher than that on cubic GaN/(100)GaAs substrates at the same HVPE growth conditions. Cathodoluminescence spectra were measured for HVPE epilayers grown on both substrates.