Investigation On The Electrical And Anti-irradition Properties Of Au/n-Hg₃In₂Te₆ Schottky Contact

Mercury indium telluride?MIT?is a novel promising ?-? compound semiconductor material,which is due to some interesting properties,such as,higher photoconductive quantum efficiency,good temperature stability,and radiation-resistant.It has been applied in the fields of aviation guidance,space exploration,optical fiber communication,nuclear power station safety monitoring,and so on.As for the Schottky photodetector with high quality,the electrical characteristics of Schottky contact can be affected by surface treatment,temperature and radiation,and so on.Therefore,it is important to study the influence of surface treatment,temperature and irradiation on the electrical characteristics of MIT Schottky photodetector,which has an important guiding significance to control the electrical performance of the MIT Schottky photodetector and to realize the industrialization of the detector.In this paper,the valence band and work function on the surface of MIT crystal were firstly studied,which was due to surface treatment.The electrical properties mechanisms of Au/n-MIT Schottky contact affected by the passivation and interlayer were explored.Meanwhile,the interface characteristics and band offsets of interlayer/MIT heterojunction were systematically analyzed.In addition,the temperature dependent of current-voltage characteristics??-??and the the deep level defects at the interface of Au/n-MIT Schottky contact were obtained respectively.The influence mechanism on ? ray irradiation of the electrical properties of MIT crystal and Au/n-MIT Schottky contact was illustrated.Under ultrahigh vacuum conditions,X-ray photoelectron spectroscopy?XPS?was used to study the valence band and work function of n-type MIT single crystal under different Ar⁺ ion etching voltage.It is found that Te and Hg concentration on the surface of MIT increased and decreased with the increasing of etching voltage respectively.Meanwhile,the surface work function increased from 4.23 eV to 4.83 eV,with the increasing of etching voltage.It was due to Te-O bond breaking and Te element clusters on the surface of MIT crystal,which can lead to the Fermi level pinning.Synchrotron radiation photoelectron spectroscopy was applied to study the valence band and work function at the surface of MIT?110?.The results showed that the valence band maximum of MIT?110?clean surface was about 0.4 eV,and the workfunction was about 4.83 eV.Then,after etching 0.5 K eV for 15 min,the cleaned and orderly surface of MIT?110?was obtaind,and the valence band maximum was about 0.6 eV,and the work function was about 4.69 eV.Here in,the concentration of Hg on the surface of MIT crystal has decreased dramatically.It can cause Fermi level pining and the dropping of vacuum level,and lead to the decrease of surface work function.The influence of H₂O₂ passivation on the electrical properties Au/n-MIT Schottky contact between Au and MIT wafer was studied by XPS and current-voltage ?-? measurement??-??.The XPS results showed that Te^2-changed into Te⁰ and HgO formed on the surface of MIT after passivation.Meanwhile,the Schottky barrier height of Au/n-MIT contact varied from 0.42 eV to 0.38 eV,and the leakage current reduced from 9.62×10^-4 A to 4.35×10^-4A after H₂O₂ passivation.It can be deduced that the passivated surface of MIT wafer decreased the number of dangling bonding,reduced the surface states,and led to the leakage current decreasing.By the means of XPS depth analysis and ?-? measurement,combined with pulsed laser deposition,the influence mechanism of the Indium tin oxide?ITO?and ZnO interlayer on the electrical characteristics of Au/n-MIT Schottky contact were analyzed.It was found that the atomic interdiffusion presented at the interface between interlayer and MIT during the deposition of ITO and ZnO interlayer.The leakage current of Au/n-MIT Schottky contact reduced from 8.1×10^-4 A to 2.3×10^-4 A,and the barrier height increased by 0.17 eV,which was due to ITO interlayer.After the ZnO introduction,the leakage current reduced from 2.3×10^-4 A to 7.3×10^-5 A,and the increase of barrier height was in agreement with the ITO interlayer.At the same time,when the ITO and ZnO interlayer were introduced,the ideal factor and resistance of Au/n-MIT Schottky contact decreased.This phenomenon can be explained that the interlayer reduced the surface states of MIT wafer and weakened the Fermi level pining,which was due to inter-diffusion.It was indicated that the interlayer introduction can improve the electrical characteristics of Au/n-MIT Schottky contacts.In situ X-ray photoelectron spectroscopy was utilized to examine the band offsets of ITO/MIT?110?and ZnO/MIT?110?heterojunctions.It was found that the atomic interdiffusion presented at the interface heterojunctions during the deposition of ITO and ZnO films.According to photoelectron spectroscopy,the valence and conduction band offset of the ITO/MIT?110?heterojunction can be calculated to be-1±0.15 eV and-3.96±0.15 eV,which is a type-? band alignment.The valence and conduction band offset of the ZnO/MIT?110?heterojunction can be calculated to be 2.3±0.15 eV and 0.46±0.15 eV,which is a type-I band alignment.The temperature dependent electrical characteristics of the Au/n-MIT Schottky contact have been studied.It was found that Schottky barrier height of Au/n-MIT contact increased from 0.39 eV to 0.5 eV and the ideality factor decreased from 3.18 to 1.88 when the temperature rose from 140 K to 315 K.Based on the plot of zero-bias barrier heights ?bo versus q/2kT,combined with Gaussian distribution of barrier height,the lateral inhomogeneity of Au/n-MIT Schottky barrier height distribution was confirmed,which was the main reason for the barrier height and the ideal factor changing with temperature.Finally,the deep levels at the interface of Au/n-MIT Schottky contact were analyzed by deep level transient spectroscopy.There were two electron trap centers at the interface of Au/n-MIT Schottky contact The defects level activation energy were 20 m eV and 278 m eV respectively,with the defect level density about 2.78×10¹⁶?1.13×10¹⁷cm^-3.By the means of Hall test,infrared transmission and ?-? test,the effect of y ray on the MIT crystal and Au/n-MIT Schottky contact were investigated respectively.The results showed that the carrier concentrations,mobility,resistivity of MIT crystals were not significantly reduced with the increase of irradiation dose,indicating that the MIT crystal has anti irradiation properties.By the means of ?-? testing,it was found that the leakage current of Au/n-MIT Schottky contact rose with increasing of irradiation dose.However,the forward saturation current and the barrier height remained unchanging.It can be explained that the interface states density increased due to new defect levels induced by irradiation,and lead to the increasing of leakage current.