Structural Properties of GaN Films with AlN Buffer Layers with Varying Growth Temperatures by Plasma-Assisted Molecular Beam Epitaxy

Abstract

We report the characterization of GaN films grown on AlN buffer layers with varying growth temperatures on sapphire (0001) substrates by plasma-assisted molecular beam epitaxy (PAMBE). GaN films grown on AlN buffer layers with varying growth temperatures were studied by means of high-resolution X-ray diffraction (HRXRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence (PL). The GaN film on the AlN buffer layer with two-step growth shows extremely narrow full-width at half maximum (FWHM) values at ω scans of XRD, symmetric (0002), and layer thickness interferences in the 2θ/ω direction. In the PL measurement, the FWHM value of the sample with a two-step AlN layer is comparatively narrow. From the SEM observation, the surface morphology has excellent surface flatness free from pits and grooves. The root mean square (RMS) of the sample surface from the AFM observation is 0.6 nm.