GAN EPILAYER ON SEPARATELY DEPOSITED BUFFER LAYER BY HOT-WALL EPITAXY

High quality GaN epilayers were grown on a sapphire substrate using a hot wall epitaxy method. We have investigated the crystal, optical, an d electrical properties of GaN epilayers grown as functions of the nit ridation condition of the substrate and the growth condition of GaN bu ffer layer. In order to study an effective method to grow a buffer lay er for the growth of high quality GaN epilayer, the buffer layers were formed on the nitridated substrate using two different methods. One i s separately deposited buffer layer (SDBL), and the other is co-deposi ted buffer layer (CDBL). It was observed that the growth condition of the buffer layer had a strong influence on the crystal and optical pro perties of GaN epilayer. A strong band edge emission peak at 3.474 eV was observed from the photoluminescence spectrum measured at 5 K for G aN epilayer grown at the optimum condition of the buffer layer. The ca rrier concentration and mobility of undoped GaN epilayer grown with a growth rate of 0.5 mu m h(-1) were 2 x 10(18) cm(-3) and >50 cm(3) V-1 s(-1) at room temperature, respectively. (C) 1998 Elsevier Science S. A. All rights reserved.