Influence of growth parameters on structural anisotropy of epitaxial a-plane GaN films

Abstract

We investigated the structural anisotropy of a-plane GaN films grown by using multi-buffer layer technique on (1-102) r-plane sapphire substrates. For high quality a-plane GaN films, multi-buffer layers with various growth conditions were grown by metal-organic chemical vapor deposition, and analyzed by using several measurement systems such as optical microscopy, scanning electron microscopy, high resolution x-ray diffraction. The experimental results showed that the nucleation-layer thickness and the growth temperature of three-dimensional (3D) growth layer affect significantly the crystal quality of subsequently grown a-plane GaN films. When the nucleation-layer thickness was 150 nm, nuclei were fully coalesced. From the x-ray diffraction results, it appeared that the growth temperature during 3D islands growth affects the full-width at half maximum (FWHM) values of x-ray rocking curves along c- or m-directions. At optimized growth conditions, the omega FWHM values of (11-20) x-ray rocking curve along c- and m-axis were 0.137° and 0.163°, respectively.