Electrical properties of GaN grown on a-plane GaN template by plasma-assisted molecular beam epitaxy

a-Plane GaN templates were grown on r-plane sapphire substrate by metalorganic vapor phase epitaxy (MOVPE) and then undoped a-plane GaN layers were grown at different growth temperatures on the a-plane GaN templates by plasma-assisted molecular beam epitaxy (PA-MBE). In order to investigate the effect of growth temperature on basal stacking fault (BSF) density and the effect of BSFs on electrical properties of a-plane GaN, background carrier concentration and electron mobility were measured by Hall measurement at room temperature. BSF density and dislocation density were also evaluated by plan-view transmission electron microscope. As the growth temperature increased from 740 to 800 degrees C, the background carrier concentration decreased from 1.4 x 10(19) to 3.2 x 10(17) cm(-3). It was observed that the electron mobility GO along c-axis [0 0 0 11 direction is larger than that (pm) along m-axis [1 (1) over bar 0 0] direction except the sample grown at 780 degrees C. The electron mobility ratio (mu(c)/mu(m)) is 0.98 for the sample grown at 780 C. Anisotropic and isotropic electrical property of a-plane GaN grown by PA-MBE is related to the BSF density. As the growth temperature was increased from 740 to 800 degrees C, the BSF density increased from 4.5 x 10(5) to 7.91 x 10(5) cm(-1). In the case of isotropic electron mobility of the sample grown at 780 degrees C, the maximum BSF density was observed. Therefore, isotropic electron mobility results mainly from the carrier scattering by the BSFs along c-axis direction. As the dislocation density was increased, the BSF density also increased. (C) 2011 Elsevier BM. All rights reserved.