High-quality GaN epitaxial films have been grown on sapphire by organometallic vapor phase epitaxy using multiple-pair buffer layers. Each pair of buffer layers consists of a thin GaN nucleation layer grown at a low temperature around 500 degrees C and a thick GaN epitaxial layer around 4 mu m thick grown at a high temperature around 1000 degrees C. The sample with four-pair buffer layers showed much improved GaN epitaxial films, as compared to the sample with only one-pair of buffer layers. The better qualities include narrower full width at half maximum of 150 arc-s and stronger intensity in double-crystal X-ray diffraction, higher electron mobility of 420 cm(2) V-s(-1), lower background concentration of 3 x 10(17) cm(-3), and lower etch-pit density of mid-10(5) cm(-2). (C) 1999 Elsevier Science S.A. All rights reserved.
MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY