Preparation And Photoelectric Properties Of N Doped P Type ZnO Materials

ZnO is a new type of wide and direct bandgap semiconductor material,the forbidden band width at room temperature is about 3.37 eV,the corresponding wavelength in the near ultraviolet region,visible light band transparent.It has many advantages such as excellent resistance to radiation,good thermal stability,non-toxic and non-polluting,rich raw materials,adjustable band width and so on,and has great potential in the field of ultraviolet optoelectronic devices.At present,although the international range of researchers have fabricated many ZnO ultraviolet optoelectronic devices with good performance by using the P-MBE,PLD and other technologies.However,there are still some problems need to be solved,such as p-type conductivity mechanism,stable and high hole concentration and mobility p-type thin film preparation process,doping technology and other in-depth study.In this thesis,we use "two-step" method to prepare N-doped ZnO thin films.Firstly,Zn3N2 thin films were deposited on quartz substrate by radio frequency reactive magnetron sputtering technique,using Zn as target,N2 as reaction gas.And then in the tube furnace the Zn3N2 turned into ZnO after high temperature oxidation,by controlling the oxidation process we could achieve the purpose of the preparing ZnO: N thin film.This method is much simpler and improves the solid solubility of N to a certain extent.We investigated the effect of nitrogen argon partial pressure,sputtering power and substrate temperature on the deposition of Zn3N2 thin films by RF reactive magnetron sputtering.We come to the conclusion that Zn3N2 thin films with good morphology and uniform film formation could be prepared under the conditions of nitrogen argon partial pressure of 2:1,sputtering power of 80 W and substrate temperature of 200?.The Zn3N2 thin film was then placed in a tube furnace and oxidized at different temperatures to convert it to ZnO: N.We used SEM,XRD,UV-Vis and other technical means to characterize the ZnO: N thin films and the conclusions are as follows.Under the conditions of oxidation temperature of 700 degree and oxidation time of 3 hours,the ZnO: N thin films exhibited good c-axis preferential orientation and the defects in the crystal were also much less.Visible light band transmittance at 90%,while in the ultraviolet band has a strong absorption,fitting to calculate the optical band gap is about 3.55 eV.The hole-concentration was 1.6×1015cm-3 and the mobility was 0.3cm2/Vs.Finally,an ultraviolet photodetector with MSM structure was fabricated by sputtering Cu interdigitated electrode on ZnO: N thin film.After annealing at 600?,the I-V test showed that the metal and the film formed a good ohmic contact.The dark current of the device is 13.4mA.With 254 nm ultraviolet mercury lamp as light source,the photocurrent was measured to be 32.2mA.Light and dark current ratio is about 2.4,it indicates that the ZnO: N thin film has a certain detection performance when subjected to 254 nm band UV light.