Effect of epitaxial temperature on N-polar InN films grown by molecular beam epitaxy

Abstract

Effect of growth temperature on 2.3μm thick N-polar InN films grown on GaN template at 440–620°C by plasma-assisted molecular beam epitaxy was investigated. We found different growth behaviors depending on the growth temperatures, which greatly influenced surface morphology. The surface showed dendritic morphologies at temperatures lower than 540°C while step-flow-like morphologies and spiral growth were clearly observed at temperatures higher than 540°C. Crystalline quality was improved with increasing growth temperature up to 540°C and was almost saturated at higher temperatures. A gradual blueshift of the emission peak was observed from 13K photoluminescence (PL) spectra with increasing growth temperature, which was due to the increased compressive strain in InN films. A Poisson ratio (ν=0.21±0.05) for InN and a slope of PL peak energy as a function of εc (δE∕δεc=18.9eV) were obtained. Our results indicated that the epitaxial temperatures of 540–600°C were best to achieve high quality InN films with a smooth surface.