The Preparation And Performance Research Of Ultraviolet Detector Based On GaN/ZnO Pn Heterostructure

With the development of human society,the application of ultraviolet photoelectric detection technology is more and more extensive,which plays a very important role in military and civil fields.With the rapid development of these fields,the demand for UV detection technology is becoming higher and higher.As the core of UV detection technology,high-performance UV detector has been widely concerned.As a kind of wide-band gap oxide semiconductor material,zinc oxide（Zn O）has the characteristics of large bandwidth（3.37 e V）,high exciton binding energy（60 Me V）,large optical absorption coefficient,simple preparation method,etc.,which makes it have great potential in photoelectric detection applications.However,due to the strong self-compensation effect,it is difficult to obtain stable p-type doping.Therefore,the preparation of heterogeneous structures by combining zinc oxide with other p-type materials is a feasible solution.Nowadays,gallium nitride（GaN）can achieve reliable and controllable p-type doping,with a band gap of about 3.44 e V at room temperature.Moreover,it has the same crystal structure as Zn O,which is wurtzite structure,and the in-plane lattice mismatch is as low as 1.8%,which can form high-quality heterostructures.Therefore,in this paper,p-type gallium nitride is introduced to construct n-Zn O/p-Ga N heterojunction UV photoelectrodetector and study its photoelectric performance.Due to the need for further optimization of its structure,its optimization was carried out in this experiment.The main research contents of this paper are as follows:Firstly,zinc oxide thin films were prepared on sapphire substrate by magnetron sputtering technology.The effects of growth pressure,sputtering power and gas flow rate on the crystal quality of zinc oxide thin films were systematically investigated.At the same time,the influence of hot annealing on the quality of zinc oxide film was also investigated.The results show that the luminescence of zno films in visible light can be significantly reduced by face to face annealing,indicating that the internal defects of zno films are obviously improved after annealing.This lays a material foundation for the subsequent preparation of heterojunction.Secondly,in order to reduce the influence of electrode contact on device performance,the contact between p-type gallium nitride and electrode was studied.In this paper,gallium nitride films were prepared on sapphire substrate by metal-organic vapor deposition（MOCVD）.The ohmic contact between different metals and gallium nitride films and between different metals and acids or bases was investigated.The results show that p-type gallium nitride can form good ohmic contact with nickel.In addition,it was found that the use of phosphoric acid to pretreat the surface of gallium nitride,coupled with subsequent rapid thermal annealing,can further reduce the ohmic contact resistance.Finally,the pn heterostructure was synthesized by combining zinc oxide with p-type gallium nitride,and the effect of Zn O layer thickness on the UV photoelectrodetection performance of the heterojunction devices was studied.In heterojunction photodetectors,only the light reaching and near the junction region can be used effectively,so the material thickness is one of the important factors affecting the device performance.The effects of different thickness of Zn O layer on the detection performance of the devices are studied.It is found that all the devices have relatively excellent UV photoelectrodetection performance,and the wide spectrum detection from the solar blind band to the visible blind band is realized.By optimizing the thickness of Zn O films,it is found that the highest responsiveness can be obtained when the thickness is 200 nm.The peak responsiveness is about 10.5 m A/W under self-bias,and the corresponding detection rate can reach 1.05×10¹² Jones.