Structural and electrical characterization of a-plane GaN grown on a-plane SiC

Planar nonpolar (11 (2) over bar0) a-plane GaN thin films were grown on (11 (2) over bar0) a-plane 6H-SiC substrates via metalorganic chemical vapor deposition by depositing a high temperature AlN buffer layer prior to the epitaxial GaN growth. The orientation of the GaN film and AlN buffer layer directly match that of the SiC substrate, as determined by on- and off-axis X-ray diffraction measurements. The morphological evolution of GaN grown on the AlN buffer layers was investigated using atomic force microscopy. Microstrucrural characterization of the coalesced a-plane GaN films provided by plan-view transmission electron microscopy revealed threading dislocation and stacking fault densities of similar to3 x 10(10) cm(-2) and similar to7 x 10(5) cm(-1), respectively. Structural comparisons to a-plane GaN films grown on r-plane sapphire substrates are presented. Si-doped films were grown with a variety of Si/Ga ratios and electrically characterized using Hall effect measurements. A maximum Hall mobility of 109 cm(2)/Vs was attained at a carrier concentration of 1.8 x 10(19) cm(-3). (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim