Optical Properties and Morphology of Gan Grown by MBE on Sapphire Substrates

Abstract

AbstractA series of GaN films grown by MBE on sapphire substrates with different nitrogen sources are characterized by optical transmission, spectroscopic ellipsometry (SE), photoluminescence (PL) and cross-sectional atomic force microscopy (AFM). The film thicknesses determined from broad spectral range transmission measurements and the AFM images are used in the analysis of the SE spectra. Interface roughnesses between the constituent layers, such as the substrate, the buffer and GaN layers are included in the modelling of the SE spectra and are also imaged by cross-sectional AFM. An effective medium type model is used for the modelling of interface and surface roughnesses in the SE spectra. The optical constants of the films in the band edge spectral range are determined in such a way as to simultaneously satisfy the transmission and the ellipsometry data.