Reducing dislocations of thick AlGaN epilayer by combining low-temperature AlN nucleation layer on c-plane sapphire substrates

Abstract

In this study, we have reported on growth of thick AlGaN layer on the c-plane sapphire substrate with low-temperature AlN (LT-AlN) nucleation layer by low-pressure metal–organic chemical vapor deposition (LPMOCVD). High resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), and photoluminescence (PL) measurements have been employed to study the crystal quality, threading dislocation density, surface morphology, and optical properties of thick AlGaN layer. Results indicate that the insertion of LT-AlN nucleation layer between sapphire substrate and high-temperature AlN nucleation layer effectively improves the thick AlGaN crystal quality, reduces the surface roughness and eliminates the threading dislocation density.