Growth of high quality a-plane GaN epi-layer on r-plane sapphire substrates with optimization of multi-buffer layer

Nonpolar (1 1-20) a-plane GaN films have been grown using the multi-buffer layer technique on (1-1 0 2) r-plane sapphire substrates. In order to obtain epitaxial a-plane GaN films, optimized growth condition of the multi-buffer layer was investigated using atomic force microscopy, high resolution X-ray diffraction, and transmission electron microscopy measurements. The experimental results showed that the growth conditions of nucleation layer and three-dimensional growth layer significantly affect the crystal quality of subsequently grown a-plane GaN films. At the optimized growth conditions, omega full-width at half maximum values of (11-20) X-ray rocking curve along c- and m-axes were 430 and 530 arcsec, respectively. From the results of transmission electron microscopy, it was suggested that the high crystal quality of the a-plane GaN film can be obtained from dislocation bending and annihilation by controlling of the island growth mode. (C) 2010 Elsevier B.V. All rights reserved.This work was supported in part by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science, and Technology (Contract no. R0A-2005-000-10079-0 and Quantum Photonic Science Research Center). S.-M. Hwang acknowledges the IT R&D program (Project no. 2009-F-022-01) by the Ministry of Knowledge Economy at Korea Electronics Technology Institute