Study On Optical Properties Of Deep UV Nitride Materials

The high A1 composition of aluminum gallium nitride(AlGaN)and AIN materials have features such as ultra-wide band gap,high temperature resistance,and radiation resistance are the preferred materials for UV LED,LD,UV detection and high power devices.However,high quality the high Al composition of AlGaN and AIN materials are difficult to prepare.Material properties prepared under different growth methods and growth conditions are quite different.Quality and properties of the device must be analyzed before application.In this dissertation,ellipsometry,Raman scattering,and transmission spectroscopy were used to characterize the optical properties,plane stress,and temperature-variation properties of AIN films and AlGaN films with different Al content.The growth of thin film materials and the preparation of high performance devices provide valuable references.The main research work of this paper is:(1)By using ellipsometry,the optical constants and temperature change properties of different thicknesses AIN films and different Al compositions AlGaN films were studied.The ellipsometric data were fitted and analyzed by dispersion models such as Tanguy and Tauch-Lorentz,and the optical constants of AIN and AlGaN were obtained in the broad band range(193 nm-1650 nm).The optical constants of AlN films with different thicknesses and AlGaN films with different Al compositions were analyzed.The thinner the thickness of AIN film,the smaller the change of band gap at different temperatures.For AlGaN samples with smaller A1 composition,the greater change in refractive index at different temperatures,and the amount of change in the optical bandgap is also greater.(2)The Raman spatial correlation model was used to analyze the plane stress of AIN films with different thicknesses and different temperatures.The results of the study show that during the growth process of AIN film,the film quality gradually increases with the increase of film thickness.The higher temperature,the greater phonon vibration and the greater shift of the high E2 vibrational modes of AlN Raman scattering,and the greater the stress in the film.Due to the different expansion coefficients of the substrate and the thin film material,the lattice mismatch rate increases.Compared with high temperature,low temperature has little effect on AIN thin films.(3)Through transmission spectroscopy,the absorption characteristics of different AIN films with different thickness and different A1 composition AlGaN were studied.Analyze the law of absorption edge and film transmittance with the change of temperature.With increasing temperature,the transmittance of the film is decreased.The band gap narrows as the temperature increases and the absorption edge red-shifts.