The Growth And Structural Properties Of Oxide Semiconductor Materials

The Zinc oxide(ZnO)is a kind of ?-? compound with excellent optical propertity and has a huge potential in the application on short wavelength photoelectric devices.Due to the problems such as the low valence band energy,the high acceptor activation energy,the low intrinsic donor activation energy and the low solid solubility of dopant,it is very difficult to obtain the reliable p-type ZnO.The lack of p-type ZnO severely hindered its development in device applications.The impurity defects of ZnO are influenced by many factors and they have an important effect on electricity,magnetic and optics properties of ZnO,so the studying and controlling the impurity defects of ZnO have profound significance on the realization of p-type ZnO and ZnO based devices.This paper deals with the above issues,focusing on controlling of impurity defects in ZnO.We further study the controlling of impurity defects of the Mono-N doping and isoelectronic co-doping technology which are considered to be the most promising technology to realize the p-type ZnO and the fabrication of the S doped alloy and low-dimension structure which are promising to reduce the difficulty of p-type doping technology.Meanwhile,we analysis the characteristics of interface of magnetic oxide heterojunction which has the important research value in spintronics.We obtain a series of innovative research results which provide the solutions and technologies for realization of p-type ZnO and ZnO based devices.The thesis mainly achieved the following results:(1)Employ the O-extreme rich condition to surpress the self-compensation.We induce shallow acceptors(NH4)Zn and(N2)Zn in N-doping ZnO successfully.The N2O acted as N dopant and abundant H in the MOCVD growth process are two important factors for the formation of(NH4)Zn and(N2)Zn.The study shows that exorbitant oxygen pressure is harmful to the formation of(NH4)Zn and(N2)Zn and the formation window is narrow.The shallow acceptors have an important influence on the electrical property of the thin film.This research has a certain value for realization of p-type ZnO.(2)Based on the principle that the O-rich thechnology will suppress the compensation donor,this paper studies the Te-N co-doping ZnO under O-rich ambinence by MOCVD and fabricated the p-type Te-N co-doping ZnO thin films successfully.The study shows that,Te prefer to occupy the Zn site and then force the N to O site,forming Tezn-No.After annealing,the Te will escape,leaving the shallow acceptor VZn-No.The C-V results show that the annealed sample is p-type and the hole concentration is about 1014cm-3.The compensation donors,like Zni-No and Hi result in the low hole concentration.The study provides a way to realize the p-type ZnO by Te-N co-doping technology.(3)According to the theory that the S-doping is benefial to improve the value band energy and lower the dopant formation energy,we developed experiment of growth ZnO1-xSx alloy by thermodynamic near equilibrium state method.The ZnO1-xSx alloy thin film and nanostructure is grown by MOCVD and CVD,respectively.Whether ZnO1-xSx alloy thin film or nanostructure is hard to obtain the he ZnO1-xSx alloy with full concentration change for the surface and substrate have different absorption coefficient for different atoms.It is very easy to form the ZnO1-xSx alloy with low S concentration(x<0.2)and high S concentration(x>0.8)and it is hard to obtain the ZnO1-xSx alloy with full concentration change.The research shows that the S-doping grown by hermodynamic near equilibrium state method is hard to control the S concentration and p-type doping as expected.(4)Based on the theory that the morphology and surface-volume ratio of nanostructure have an important influence on its optic property and doping,we obtain ZnO nanowire,nanosheet and nanoarray by CVD successfully.Fabricated ZnO nanosheet FET and the electricity characterization shows that the threshold voltage Vth=3.33V,the mobility is high reach 175 cm2V-1s-1,indicating that ZnO nanosheet have high quality.In addition,after Ar plasma,the near band emission of ZnO nanoarray is enhanced and the green band emission is weakened.It indicates that the Ar plasma can reduce surface defects of ZnO nanoarray,improving the surface state.The study provides a way to improve the performent of ZnO nanostructure base photoelectric devices.(5)Based on the the study of Fe3O4 which combine the semiconductor and magnetic properties has an important value on development of spintronics.We grow Fe3O4 thin films on oxide substrate(Al2O3 and ZnO)by MOCVD and analysis the interface and the thermos-stability of samples in detail by high temperature annealing.The reseach shows that there are atoms inter-diffusion at the interface and the annealing enhanced the Zn diffusion while nearly have no influence on the A1 diffusion.The annealing also improves the Fe3O4 quality due to the Fe vacancy and metal Fe vanished.The low concentration Zn and Al diffusion is advantage to improve the saturation moment of the samples while the high concentration Zn and Al diffusion will reduce the saturation moment.This conclusion is helpful to realize the spin-LED.(6)Based on the advantage of nitrides on p-type doping and spin-devices,we study the Fe3O4 thin film grown on GaN,especially the influence of the insert layer Ga2O3 on the interface and magnetic propertices of Fe3O4/GaN by MOCVD.XPS results show that there are exist alloy layer resulted by Ga,Fe inter-diffusion at the Fe3O4/Ga2O3 interface.Annealing enhance the inter-diffusion and then Increase the thickness of the alloy layer,changing the magnetic properties of the samples a lot.The freezen-moment are observed before annealing while no after annealing.The MR-T curve shows that the spin-dependent current dominated in the sample before annealing and the spin-independent current dominated in the sample after annealing.The annleaing enhanced the Ga diffusion and then weakened the magnetic peopertity of samples.This research has a certent reference value for fabricating GaN based spin devices.