| Gallium oxide not only possesses many unique and excellent physical properties,but also becomes more and more mature in the preparation technology of gallium oxide single crystal substrate,epitaxial film,nanostructure material.Thus,it has a wide application prospect in solar-blind photodetector,power transistor,ultraviolet-transparent conductive electrode,LED,resistive random access memory,gas sensors and so on.High quality epitaxial film growth technology is the key factor of the Ga2O3 material application in optical electronic devices.In this dissertation,we mainly take advantages of wide bandgap and large breakdown electric field of gallium oxide.Based on the demand of device design and preparation,the controlled growth of gallium oxide epitaxial thin film is explored to study optical,solar-blind optoelectronic,electrical properties of the epitaxial thin films and their applications in solar blind detector,phototransistor and field effect transistor.The main research results are as follows:(1)?-Ga2O3 thin films with different crystal quality,morphology and optical bandgap have been obtained by tuning the growth temperature and post-annealed treatment.Solar-blind photodetectors based on ?-Ga2O3 thin films have been fabricated.Higher crystal defect and oxygen vacancy density make the thin film higher responsivity,and it also makes the spectral selectivity of the film worse and the response speed slower.Large size crystal grain can greatly reduce the grain boundary scattering effect,which allows the film to obtain higher photocurrent gain and faster response speed.(2)Through the doping of Al,the free energy of the system have been adjusted,and a thermally stable metastable phase ?-Ga2O3 thin films have been successfully grown by magnetron sputtering at 750 ?.The solar blind optoelectronic properties of ?-Ga2O3 thin film are reported for the first time.Benefitting from high crystal quality and absence of oxygen vacancies in ?-Ga2O3,the device exhibits high rejection ratio of solar blind versus solar visible and fast response speed.By introducing Al2O3 ultrathin film,we can realize the stress modulation during the growth of the thin film,thus the controllable growth of the surface morphology of the ?-Ga2O3 film from one-dimensional to two-dimensional has been successfully achieved.?-Ga2O3:Al2O3 nanowires films have larger surface-to-volume ratio and stronger light scattering effects,which can benefit the higher responsivity of films to the incident solar blind light.(3)?-(Al,Ga1-x)2O3 and(Ga1-x-yFexAly)2O3 thin films have been grown by alternative deposition technique and post-annealed treatment,which have a maximum bandgap of 6.12 eV and bandgaps ranging from 4.96 to 5.99 eV respectively.(Ga1-x-yFexAly)O3 with excellent insulating and dielectric properties can be used as buffer layer between the substrate and channel layer,and passivation layer between the channel layer and insulating layer for the MOSFET preparation based on Ga2O3.By introducing of ?-In2O3 cathode buffer layer,the electric properties of?-Ga2O3 thin film can be successfully tuned.The ?-Ga2O3/?-In2O3 bilayer films exhibit high carrier mobility of 25.5 cm2/V·s,which will benefit the preparation of high mobility field effect transistor.(4)The back gate and top gate solar blind-ultraviolet phototransistors have been designed and successfully been prepared based on the Ga2O3 thin films.The back gate phototransistor is an enhancement-mode MOSFET with n-channel,the threshold voltage and field-effect mobility are 1.12 V and 6.19×10-2 cm2/V·s respectively.Moreover,the back gate phototransistor can obtain 3.58 times photocurrent gain with +40 V gate voltage applied,which exhibits good gate voltage manipulation characteristics of the device.The top gate phototransistor is a depletion-mode MOSFET with n-channel,the on/off ratio of drain current and field-effect mobility increase gradually with increasing incident light intensities.The drain current on/off ratio and breakdown electric field are 1.20×104 and 2.1×10-2 cm2/V·s respectively under 500 ?W/cm2 of 254 nm light illuminations. |
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