Effect of initial layers for high-quality GaN growth by hot-wall epitaxy

We report the initial growth stage of GaN film on sapphire substrate by hot-wall epitaxy (HWE) technique. Roughness of the substrate surface for high-quality GaN film deposition can be controlled by the initially nitridated layers. We form the nitridated layer on a sapphire (0 0 0 1) surface under the ambient ammonia gas and the substrate temperature of 1050 degrees C. The initial layers are grown on the nitridated layer. The GaN epilayers are grown on the initial layer and their opto-electronic properties are examined. The photoluminescence characteristics of GaN epilayers shows strong band edge emission peaks at 3.474 eV and very weak emission in the yellow spectral region. Undoped GaN epilayer grown at around 1 mu m/h shows the carrier concentration of low 10(18) cm(-3) and mobility of up to 50 cm(2)/V s at room temperature. (C) 1998 Elsevier Science B.V. All rights reserved.