Mixed Phases at the Bottom Interface of Si-Doped AlGaN Epilayers of Optoelectronic Devices

Abstract

This paper presents an analysis of crystalline structures of Si-doped Al0.4Ga0.6N layers grown on not-intentionally doped AlGaN buffer layer with an AlN nucleation layer by metal organic chemical vapor deposition. Weak cubic Al0.4Ga0.6N (002) and (103) reflection peaks are observed in high-resolution XRDθ/2θscans and cubic Al0.4Ga0.6N (LO) mode in Raman scattering spectroscopy. These cubic subgrains are localized at the bottom interface of Si-doped layer due to the pulsed lower growth temperature and rich hydrogen atmosphere at the start of silane injection. Their appearance has no direct relationship with the buffer and nucleation layer. This study is helpful not only to understand fundamental properties of high aluminum content Si-doped AlGaN alloys but also to provide specific guidance on the fabrication of multilayer optoelectronic devices where weak cubic subgrains potentially occur and exert complicated influences on the device performance.