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

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.

► Thick AlGaN epilayer was growth by combining LT-AlN nucleation layer using LPMOCVD.
► Dislocations of AlGaN epilayer were eliminated by combining LT-AlN nucleation layer.
► Surface roughness of AlGaN layer was reduced by combining LT-AlN nucleation layer.
► Insertion LT-AlN nucleation layer can enhance the optical property of AlGaN layer.