Study On The Improvement Of The Performance Of ZnO Light-emitting And Detecting Devices By The Regulation Of Intrinsic Defects

In recent years,semiconductor materials play an important role in daily production and daily life.As a kind of direct band gap semiconductor,ZnO has a band gap of 3.37 eV,exciton binding energy of 60 meV,strong radiation resistance,high electron saturation drift rate and thermal stability.It has shown great application potential in ultraviolet light-emitting,laser and detection optoelectronic devices.However,due to the lack of efficient and stable p-type doping technology,the development of ZnO based p-n homojunction optoelectronic devices is seriously hindered.Therefore,p-GaN/n-ZnO heterojunction and metal semiconductor metal?MSM?planar structure have become the mainstream structures of ZnO based light-emitting diode?LED?and UV photodetector,respectively,and have made great progress.As we all know,the intrinsic defects such as oxygen vacancy in ZnO materials often lead to its high conductivity?proportional to the product of electron concentration and mobility?,which has a serious impact on the performance of its UV electronic devices.For example,the luminescence of p-GaN/n-ZnO heterojunction does not come from the side of ZnO,the dark current of ZnO MSM UV detector is very large,and the signal-to-noise ratio is low.To solve this problem,the performance of ZnO based optoelectronic devices has been greatly improved by effectively controlling the intrinsic donor defects in ZnO materials.The main achievements are as follows:1.By adjusting the intrinsic donor defects and electron mobility in ZnO thin films,the wavelength and source of p-GaN/n-ZnO heterostructure LED luminescence can be effectively controlled,which solves the problem that it is difficult to obtain the luminescence from ZnO layer in traditional heterostructure devices.In this paper,we use MBE equipment to control the growth conditions to control the intrinsic defects of the material,such as crystal quality and oxygen vacancy.We obtain ZnO films with continuously adjustable mobility and carrier concentration,and construct p-GaN/n-ZnO heterojunction LED.The results show that as the electron mobility of ZnO decreases,the light source of the device gradually shifts from GaN side to ZnO side.When the electron mobility of ZnO is 1.7 cm²v^-1s^-1,the UV electroluminescence with wavelength of 376 nm is realized.2.In the p-GaN/n-ZnO heterojunction LED,UV emission is obtained for the first time under both positive and negative bias voltage,and the relevant mechanism is clarified,which provides a new working mode for high-performance heterojunction UV light-emitting devices.Under the positive bias,because the conduction band order and valence band order of p-GaN and n-ZnO are basically the same,and the mobility of electrons in ZnO is significantly smaller than that of holes in GaN,the holes from GaN can be injected into one side of ZnO very quickly,while the electrons from one side of ZnO inject into the interface or one side of GaN relatively less,so UV light emission is realized.Under the reverse bias,the tunneling of electrons from the full band on the GaN side also achieves the near band edge ultraviolet emission on the ZnO side.3.By treating the surface of ZnO film with NH_3?H₂O solution,the surface defects are reduced,the dark current of the device is significantly reduced,the responsivity of the device is improved,and the response speed of the device is improved,which provides a new way to realize high-performance ZnO UV detector.The intrinsic defects on the surface of ZnO material are one of the key factors that cause the poor performance of its photoelectric devices.In this paper,the treatment of ZnO surface with NH_3?H₂O solution is studied.It is found that the reaction of NH_3?H₂O with ZnO reduces the surface defects of ZnO,weakens the process of oxygen adsorption and desorption,passivates the surface,and improves the response speed of the device?the response time is reduced from 316 s to 7 s?,The dark current of the device is reduced by about three orders of magnitude,and the improvement of the flatness of the sample surface reduces the probability of the recombination of photocarriers on the surface,and improves the response of the device by about two times.