Characterization of high quality InN grown on production-style plasma assisted molecular beam epitaxy system

Abstract

In this work, the authors report step-flow growth mode of InN on [0001] oriented GaN templates, using a production-style molecular beam epitaxy system, Veeco GEN200®, equipped with a plasma source. Using adaptive growth conditions, they have obtained a surface morphology that exhibits the step-flow features. The root mean squared roughness over an area of 5×5μm2 is 1.4nm with monolayer height terrace steps (0.281nm), based on atomic force microscopy. It has been found that the presence of In droplets leads to defective surface morphology. From x-ray diffraction, they estimate edge and screw dislocation densities. The former is dominant over the latter. Micro-Raman spectra reveal narrow E22 phonon lines consistent with excellent crystalline quality of the epitaxial layers. The Hall mobility of 1μm thick InN layers, grown in step-flow mode, is slightly higher than 1400cm2∕Vs, while for other growth conditions yielding a smooth surface with no well-defined steps, mobility as high as 1904cm2∕Vs at room temperature has been measured. The samples exhibit high intensity photoluminescence (PL) with a corresponding band edge that shifts with free carrier concentration. For the lowest carrier concentration of 5.6×1017cm−3, they observe PL emission at ∼0.64eV.