Improvement in structural and electrical characteristics of nonpolar a-plane Si-doped n-AlGaN

Abstract

Nonpolar Si-doped AlGaN with high electron concentration (EC) and superior surface morphology (SM) layers were successfully grown on r-plane sapphire substrates for the first time with metal organic chemical vapor deposition technology. X-ray diffraction, cross-sectional scanning electron microscope, ultraviolet–visible absorption spectroscopy, atomic force microscopy, and Hall measurements were used to examine the influence of indium surfactant and an extra AlGaN buffer on crystalline quality (CQ), SM, and electrical characteristics of the nonpolar Si-doped n-AlGaN, respectively. The characterization results revealed that the anisotropy in CQ of the nonpolar Si-doped n-AlGaN epi-layers was suppressed effectively, and the SM, as well as the electrical properties including EC, electron mobility (EM), and electron resistivity (ER), had been significantly improved by using indium surfactant and an extra AlGaN buffer layer. In fact, an EC as high as 4.8 × 1017 cm−3, an EM up to 3.42 cm2/V s, an ER down to 4.78 $$\Omega \bullet $$cm , and a root-mean-square value as small as 8.2 nm for surface roughness was achieved for the nonpolar Si-doped n-AlGaN with a relatively high Al composition of 50%.