Annealing Study Of Wide Bandgap Materials Based On Gallium Oxide

?-Ga₂O₃is a new wide bandgap oxide semiconductor material with good chemical and thermal stability,whose bandgap is about 4.9 eV,Hence,?-Ga₂O₃can be widely used in ultraviolet photodetector,power devices and so on.However,lattice mismatch and thermal mismatch between substrate and epitaxial layer cause lots of point defects,dislocation and so on,which are closely related with decives'work efficiency and reliability.In this paper,As-grown?-Ga₂O₃and?-(Al_xGa_1-x)₂O₃samples were annealed at different temperature,ambient and duration.And the effect of these parameters on crystal quality,surface morphology,optical property,surface chemical composition and chemical state were studied.In addition,solar-blind ultraviolet detectors were fabricated on?-Ga₂O₃films,the influence of annealing ambient on the detectors'performance and the micromechanism were studied.The details work are as follows.Firstly,under the annealing temperature of 700 degree centigrade,as the duration of annealing grows,the films'crystal preferred orientation improved.the films'roughness remain unchanged.the absorption edge shift towards the blue end of the spectrum.and optial bandgap increased.When annealing temperature reaches 900 degree centigrade,the diffraction peak move to small angle,This is because the stress introduced by high annealing temperature lead to lattice distortion,and its contribution to lattice is larger than interdiffusion.When annealing temperature increase up to 1000 degree centigrade,the peak diffraction peak shift towards small angle first and then shift towards large angle,this is because high temperature and annealing duration has promoted interdiffusion greatly.For optical characteristic,as the duration of annealing grows,the transmittance increased firstly and then decreased,this is in accord with the results of films'surface morphology.Secondly,for the films annealed in different ambient,annealing ambient has little effect on the crystal structure of?-Ga₂O₃under the annealing temperature of 800degree centigrade,and nitrogen has the relatively better consequence.For surface morphology,surface smoothness improved.For the transmission spectrum,the absorption edge of the films annealed in nitrogen and air shift towards the blue end of the spectrum slightly.The bandgap increased as well.For the film annealed in oxygen,the absorption edge shift towards the red end of the spectrum slightly.This is because oxygen introduced interstitial atoms,and these defect level will absorb low frequency light.Thirdly,the I-V curves of photodetectors show that the detector prepared on the film annealed in nitrogen has the maximal photocurrent.The photocurrent of samples annealed in air and oxygen is smaller than reference,because the better the crystal quality is,the easier the carriers move and the bigger the conductance is.On the contrary,deteriorated samples can scattering the carriers and result in smaller photocurrent.For the time response,the rise time and fall time both decreased after annealing.And the detector prepared on film annealed in oxygen has the shortest fall time,because the films annealed in oxygen has the least oxygen vacancy.And the number of free electrons on the film's surface decreased.So the effects of oxygen adsorption and ionization is weaken.Therefore,we should choose the reasonable annealing condition according to the requirements of devices.Finally,For ?-(Al_xGa_1-x)₂O₃films,under the annealing temperature of 800 degree centigrade,the diffraction peak shift towards to small angle slightly.And the peak intensity of the film annealed in nitrogen is strongest.Other samples almostly remain unchanged.the absorption edge and bandgap almost keep unchanged.Under the annealing temperature of 1000 degree centigrade,results show that annealing has a good influence on?-(Al_xGa_1-x)₂O₃films.And nitrogen is the best atmosphere for improving film's crystal quality.Meanwhile,the absorption edge shift towards to blue end of the spectrum and optical bandgap increased.the RMS roughness increased slightly.The results of XPS reveal that the films are oxygen deficient.The Ga in films exists inGa^3?10?,Ga^2?10?,Ga^?10?form.The amount of oxygen increased after annealed,this is because oxygen entered lattice and oxygen vacancy decreased.Meanwhile,the binding energy of Ga3d and O1s increased after annealing,the full width at half maximum deceased obviously.and the peak intensity is stronger.The results prove that the energy of Ga-O and Al-O increased and the quality of chemical bond improved.The signal peaks of N1s reveal that new nitrogen was introduced after annealing.