Reaching Of Heteroepitaxial C-axis Oriented GaN Thin Films By Sol-gel

Gallium nitride（GaN）is a direct wide band gap（3.4 e V）semiconductor material,because of its unique properties have been widely used in many fields such as in the optoelectronics GaN based high efficiency blue and green LED large screen full-color display,saving and environmental protection than ordinary incandescent lamp 5-10 times,can be prepared by high frequency and high power electronic devices are expected to play an important role in the aerospace and other special environment using GaN materials in microelectronics,the research and application of semiconductor become a hot research topic in global scope.Aimed at the process and cost drawbacks of current mainstream methods for preparing thin films,such as MBE,MOCVD,HVPE,etc High quality GaN thin films were prepared by simple sol-gel method.The heteroepitaxy c-axis orientation nanoscale GaN films were prepared by using GaCl₃ as a source of niobium and NH₃ as a nitrogen source by coating rotation and high temperature amination annealing.The following main conclusions are obtained:（1）Respectively using different concentrations（0.1M-0.5M）of reagents,different annealing temperature（700°C-900°C）and different annealing time（1h-3h）and different solvents（EA,DEA）GaN films.Through XRD,SEM and other characterization methods,it was found that 0.2M,900°C,2h,DEA were the best reaction parameters and the preferred orientation of the crystal plane was calculated as the c-axis orientation of the（002）crystal plane by calculating the diffraction intensity.（2）Photoluminescence（PL）and Raman spectroscopy indicated that the GaN/Si（111）had some red-shifted diffraction peaks around 376nm,396nm and 438nm,and the GaN thin film material prepared by this method had the E1（TO）mode.With a slight movement,the grain size is about 5 nm,so it can be considered that the movement of the peak is caused by the effect of the nano-grain size.A1（LO）phonon mode and E2（high）peak show that the GaN/Si（111）thin film material has an internal stress of 0.5GP.（3）The results of energy dispersive spectroscopy（EDS）and photoelectron spectroscopy（XPS）show that the ratio of Ga and N atoms in the GaN thin film material is22.57:2.12 and the GaN film material obtained by this method has no impurity except C and O elements.It is relatively pure.By analyzing the O element,the oxygen is not bound to oxygen.Therefore,it is inferred that there is no Ga₂O₃ generation in the film.（4）The use ofα-Al₂O₃ as a base material in the study of the epitaxial properties of GaN films was analyzed to compare the effects of using different substrate materials（α-Al₂O₃,Si）on the film quality and to give a reasonable explanation.At the same time,it was found that the temperature increase of GaN films.The epitaxy has greatly improved and the full width at half maximum（FHWM）is continuously decreasing.The calculation of the Scherrer’s formula shows that the grain size of the thin film belongs to the nano level and the grain size increases with the increase of temperature.