Microstructure and physical properties of GaN films on sapphire substreates

摘要

Transmission electron microcopy (TEM), x-ray diffraction (XRD), photoluminescence )PL) and Raman scattering measurements were applied to study the correlation between the microstructure and physical properties of the GaN fims grown by light radiation heating metalorganic chemical vapordeposition (LRH-MOCVD), using GaN buffer layer on sapphire substrates. When the density of the threading disolation (TD) increases about one order of magnitude, the yellow luminescence (YL) intensity is strengtheneded from negligible to two orders of magnitude higher than the band edge emission intensity. The full width of half maximum (FWHM) of the GaN (0002) peak of the XRD rockingcurve was widened from 11 min to 15 min, and in Raman spectra, the width of E_2 mode is broadened from 5 cm~(-1) to 7 cm~(-1). A "zippers" structure at the interface of GaN/sapphire was observed by high-resolution electron microscope (HREM). Furthermore the origins of TD and relationship between physical properties and microstructures combining the grwoth conditions are discussed.