Improvements in characteristics of N-polar Si-doped AlGaN epi-layer grown on mis-oriented c-plane sapphire substrate

Abstract

The N-polar Si-doped n-type AlGaN epi-layer with an Al composition up to 54% was successfully grown on vicinal c-plane sapphire substrates by metal-organic chemical vapor deposition technology. High-resolution X-ray diffraction, atomic force microscopy, and Hall effect measurement were used to evaluate the influence of the use of vicinal sapphire substrate on the crystalline quality, the surface morphology, and the electrical property of the N-polar Si-doped AlGaN epi-layer, respectively. The characterization results reveal that the use of an optimized vicinal sapphire substrate plays a vital role in the improvements in the crystalline quality, the surface morphology, and the electrical property for the N-polar Si-doped n-type AlGaN epi-layers. In fact, a relatively smooth surface morphology with a root-mean-square value as small as 17.3 nm, an electron concentration of 1.9 × 1019 cm−3, and an electron mobility of 23.5 cm2 V−1 S−1 were achieved with the N-polar Si-doped n-type AlGaN epi-layer sample grown on a 1° mis-oriented c-plane sapphire substrate in this study.