Structural and optical analyses of AlxGa1−xN thin films grown by metal organic chemical vapor deposition

Abstract

A series of AlxGa1−xN thin films with x = 0.20–0.60 were grown by metal organic chemical vapor deposition (MOCVD) on sapphire (0001) substrate using AlN buffer layer. High resolution X-ray diffraction (HRXRD) was performed for (0002), (0004), and (0006) reflections to investigate the threading dislocation density in variation with Al composition by X-ray analysis technique; Williamson–Hall (WH) plot. A symmetric high resolution 2θ–ω scans exhibit high crystal quality for all the AlGaN samples. A room temperature deep ultraviolet (DUV) photoluminescence (PL) spectroscopy (excitation at 248 nm) has also been employed to investigate the effect of various Al compositions on crystal structure of the thin film layers. It was observed that the band edge transition peak energy blueshifts from 3.87 eV for x = 0.23 to 4.55 eV for x = 0.47. In addition to the band edge transition, each spectrum also shows deep impurity transitions.