Semipolar (112¯2) GaN Films Improved by in situ SiNx Pretreatment of m‐Sapphire Substrate Surface

Abstract

The authors report on growth and characterization of semipolar () GaN films improved by an in situ SiNx pretreatment of m‐sapphire substrate surface. Formation of SiNx and Ga‐rich surface at the initial growth stages is evidenced by X‐ray photoelectron spectroscopy. With the SiNx pretreatment, the GaN nucleated island density decreases due to the reduction of nucleation density by the SiNx mask. X‐ray diffraction and Raman analyses show reduction of threading defect density for the SiNx pretreated GaN films. Cathodoluminescence studies show enhanced D0X emission and suppressed defect‐related emissions. The improvements in crystalline quality and optical properties of semipolar GaN films with the SiNx pretreatment are attributed to the reduction in nucleated island density and coalescence boundaries, and enhancement of the +c island sidewall facet growth under Ga‐rich growth conditions.