Surface preparation for gallium nitride thick layers deposition by HVPE

Low-temperature gallium nitride buffer layers (LT-GaN) deposition preceded growth of high temperature gallium nitride (HT-GaN) thick layers. Buffers and thick layers were deposited on (0001) sapphire substrates by Hydride Vapor Phase Epitaxy (HVPE). Before nucleation layer deposition sapphire substrates were chemically and thermally treated in various ways. Substrate surface morphology was examined by Atomic Force Microscopy (AFM). Properties of GaN layers were investigated by AFM, Photoluminescence (PL), and micro-Raman measurements.