Luminescence, morphology and X-ray diffraction features of InGaN materials grown on sapphire by metalorganic chemical vapor deposition

Abstract

InGaN thin films were grown by low-pressure metalorganic chemical vapor deposition (MOCVD) and characterized by photoluminescence (PL) with variable excitation intensity and temperature, room-temperature cathodoluminescence (CL), high resolution X-ray diffraction (HRXRD), scanning-electron-microscopy (SEM) and atomic force microscopy (AFM). For PL, all the samples show dominant peaks at around 2.9 eV and extra peaks or shoulders at 2.8 eV at 6 K. We concluded that the low energy peak is due to the localized near-band edge transition from the phase-separated InGaN mesoscopic structure with high In-content. The strong luminescence of the low energy peak at room temperature is due to the quantum confinement enhancement in the form of nanostructures or quantum dots. AFM images showed that phase-separated InGaN samples have inverted hexagonal pits which are formed by the In segregation on the (1011) surfaces. Room temperature cathodoluminescence (CL) and images at wavelengths corresponding to the GaN band edge, the In-poor and In rich regions were studied. It was shown that phase separated In-rich regions formed at the periphery of the hexagonal pits.