Study Of Single Crystal β-Ga₂O₃ Film Prepared By Sol-Gel Method

β-Ga₂O₃is an ultra-wide bandgap semiconductor material（～4.9eV）,its band gap and Barriga are much larger than GaN and Si C,which can provide higher breakdown voltage and lower On-resistance(R_on).At the same time,β-Ga₂O₃with excellent ultraviolet-light transmission characteristic has unique advantages in optoelectronic devices,solar-blind ultraviolet photodetectors,and ultra-high-efficiency,low-loss devices.In addition to being a semiconductor material for high-performance device,β-Ga₂O₃can be used as a substrate material for epitaxial GaN due to its small lattice mismatch（～2.6%）.In the previous research of our laboratory,theβ-Ga₂O₃film has been nitridated and converted to porous GaN substrate,which was successfully applied to the preparation of low-stress GaN free-standing substrates.The overall aim of this thesis is to prepare gallium oxide（Ga₂O₃）single crystal film by the sol-gel spin coating method,and to study the influence of sol-concentration,preheating temperature and spin coating times on the crystal structure,surface morphology and optional property ofβ-Ga₂O₃film.The Sol-Gel method is a simple,economical and efficient process that doesnot require expensive equipment,vacuum environment,substrate conductivity and other special requirements to prepare large-area uniform films.The Sol-Gel and spin coating methods provide an inexpensive and readily accessible route for the preparation of oxide single crystal films,and can also be used for the preparation of low-stress GaN substrate materials.This thesis mainly focuses on the preparation of large-sizeβ-Ga₂O₃single crystal films on c-plane sapphire substrate by the sol-gel-spin coating method.The influence of process parameters such as sol-concentration,preheating temperature and spin coating times on the preparedβ-Ga₂O₃film was systematically studied,and the crystal structure,surface morphology and optical properties was characterized and discussed.The main research results include:1.The 2-inchβ-Ga₂O₃single crystal film with（（?）01）preferred orientation was successfully prepared on the c-plane sapphire substrate by spin coating method and spin coating process,and the FWHM of the（（?）01）characteristic peak is 0.831°.Theβ-Ga₂O₃film has a smooth surface,high transmittance in the Near-Ultraviolet-visible region,and its optical band gap is about 4.8 eV.2.The process of preparing（（?）01）orientedβ-Ga₂O₃films with different sol-concentration was studied.When prepared at a low sol-concentration,theβ-Ga₂O₃film has only a weak（（?）01）diffraction peak.With the increase of the sol-concentration,theβ-Ga₂O₃film showing obvious（（?）01）preferred orientation appeared（（?）02）and（（?）03）diffraction peaks,the intensity of the（（?）01）diffraction peak gradually increased,but the film crystal quality was low.When the sol-concentration is too high,the uniformity and light transmittance of theβ-Ga₂O₃film will deteriorate.3.The effect of different preheating temperature on the preparation ofβ-Ga₂O₃films with（（?）01）preferred orientation were studied.When prepared at a low preheating temperature,theβ-Ga₂O₃film suffered from powdering and cracking,which affects the transmittance and optical band gap.Additional,properly increasing the preheating temperature can improve the crystallinity of the film,reduce the degree of cracking,and improve the optical properties of theβ-Ga₂O₃film.4.The influence of different spin-coating times on the preparation ofβ-Ga₂O₃films with（（?）01）preferred orientation was studied.With the increase of the time of spin coating,the intensity of the diffraction peak ofβ-Ga₂O₃film（（?）01）gradually increases,while the degree of（（?）01）preferred orientation decreases.Properly increasing the time of spin coatings can improve the surface morphology of the film and make its grain size and distribution uniform.5.Theβ-Ga₂O₃film prepared by sol-gel method was nitrided at high temperature to obtain porous GaN single crystal film with c-axis orientation,which has higher crystalline quality and lower stress,and the FWHM of the（002）characteristic peak is1.148°.It can be used as the template for HVPE epitaxial growth in our laboratory.