| As an ultra wide band gap semiconductor,?-Ga2O3 has the advantages of large band gap(4.5?4.9 e V),high breakdown field strength(8 m V/cm)and radiation resistance.It is a new type of semiconductor material with broad application potential,especially in the fields of high power devices,solar-blind and X-ray photodetectors.Fe is a common capture trap in semiconductors.The Fe impurity is intentionally mixed into?-Ga2O3 crystal to compensate the intrinsic n-type conductivity of?-Ga2O3,which is used to form semi-insulating high-resistance single crystal.Fe-doped?-Ga2O3 single crystal(Fe:?-Ga2O3)is generally used as a high performance homogeneous epitaxial substrate for gallium oxide based devices to reduce the leakage current generated in the operating state.Because the substrate does not act as the main operating region of the device,there are few basic studies on Fe:?-Ga2O3.Aiming at these problems,first of all,guided mode method is used to grow 0.05%Fe:?-Ga2O3 single crystal,and then through the combination of a variety of testing methods,systematically studied the addition of Fe in?-Ga2O3 microstructures,optical and electrical properties of crystals and the effects of the annealing further analyzes the Fe in the capture function of?-Ga2O3,including the following aspects:1.Combined with Raman scattering spectra,Electron Paramagnetic Resonance(EPR),and high-resolution XRD(HR-XRD)results,which proved that crystal has monoclinic structure and Fe will preferentially replace octorhedal without destroyed crystal structure.Quantitative analysis of EPR shows that the number of Fe3+spins after air annealing is halved from 3.077×1016 spin/mm3 to 1.877×1016 spin/mm3.2.X-ray photoelectron spectroscopy(XPS)was used to analyze Ga,O and C elements in detail.By comparing the bonds and Ga/O ratio after air annealing treatment,the possible existence mode of C element in the crystal cause the deterioration of electrical conductivity.It was concluded that the introduction of C pollution should be avoided in the growth process.3.Through UV photoelectron spectroscopy,we obtained that the fermi level of Fe:?-Ga2O3 moves from 3.94 e V to 3.78 e V after air annealing,and the I-V current shows that the resistance increases from 5.98×1011?cm to 8.94×1011?cm.It shows that air annealing improves the high resistance property.Combined with the spin number of Fe3+,the effect mechanism of annealing on the conductivity property is analyzed.4.The differences between Fe:?-Ga2O3 photoluminescence(PL)spectra andX-ray excited luminescence(XEL)have been compared.Due to the fluorescence quenching effect of Fe,the defect luminescence signal in the photoluminescence spectra only appears in the red band,which is attributed to nitrogen element.A weak signal of defect emission is generated by X-ray excitation,and then proved that the green band was vacancies of tetrahedral gallium site VGa?2–in?-Ga2O3.5.On the semi-insulated Fe:?-Ga2O3 samples,the method of ohmic contact electrode was studied.The photocurrent,darkcurrent and responsiveness of MSM X-ray photodetectors base on Fe:?-Ga2O3 single crystals have been analyzed.All of the detectors have darkcurrent with a lower extent (?10-3 n A)and fast response time less than 0.16 s. |
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