Design,fabrication And Characteristics Of High Performance ZnMgO UV Photodetectors

In recent years,ultraviolet(UV)detection technology has shown great potential in the military and civil fields,such as flame detection,missile guidance,secret communication and so on.As a direct wide band gap(3.37 e V)semiconductor material,Zn O alloy with adjustable band gap from 3.3 e V to 7.8 e V can be achieved by Mg doping.Due to its excellent photoelectric properties,it is considered to be one of the most ideal materials for solar blind and visible blind UV detectors.After years of development,ZnMgO based UV detectors have achieved a series of important research results.However,in order to meet the requirements of high stability,low energy consumption,and high responsivity of the detector in the actual application process,the comprehensive performance of the current ZnMgO ultraviolet detectors still have a lot of room for improvement.It is necessary to further improve the responsivity of existing devices,reduce dark current,increase response speed,and improve spectral response characteristics.In this paper,starting from the aspects of controlling the state of thin film surface defects,designing the energy band structure of the device,improving the quality of thin film crystals and electrical properties,etc.,the overall performance of the ZnMgO-based UV detector was effectively improved.The specific results were obtained as follows:1.The defects on the film surface were controlled by hydrogen peroxide solution treatment,which effectively improved the comprehensive performance of ZnMgO UV detector,and provided a simple and efficient method to improve the performance of oxide semiconductor devices.After hydrogen peroxide treatment,the dark current of the device was reduced by an order of magnitude,the response speed in vacuum was reduced from more than 10 h to less than 1 s,and the sensitivity of device performance to atmosphere was effectively reduced.It can be inferred from the PL test results of the films and the I-t curves of the devices in different atmospheres that these changes are due to the effective removal of oxygen defects on the surface of the films by hydrogen peroxide treatment.2.The use of AlN as a buffer layer improves the crystal quality of the high-Mg ZnMgO film,comprehensively improves the comprehensive performance of its corresponding deep ultraviolet photodetector,and provides a new way to improve the quality of ZnMgO materials and device performance.The buffer layer process can effectively improve the crystal quality of epitaxial grown high Mg content ZnMgO films.As a buffer layer,AlN has a wider band gap than the upper active layer,which can avoid extra optical response in UVA band.At the same time,its ultra-high resistivity can further reduce the dark current of the device.Compared with the device directly grown on the c-Al₂O₃ substrate,the dark current was reduced by about an order of magnitude,the oxygen adsorption and desorption process was weakened,and the response speed was also significantly improved.In addition,the main light response parameters,such as peak responsivity,ultraviolet-visible light suppression ratio and response cut-off edge,had been improved to some extent.3.By improving the crystal quality and conductivity of the active layer,and optimizing the energy band structure of the device,a high-performance p-GaN/n-ZnMgO heterojunction self-powered ultraviolet detector was prepared.Compared with the reported work,this paper uses MBE's advantages in the preparation of doped semiconductors,on the one hand to grow p-GaN with better electrical properties and crystal quality to reduce the series resistance in the device;on the other hand,it uses band gap Wider ZnMgO replaces ZnO as the n-type layer.Compared with GaN(3.40 e V),the ZnMgO(3.51 e V)grown in this paper has a larger band gap,which can make most of the ultraviolet light reach the space charge region more effectively and enhance the photocurrent.The prepared p-GaN/n-ZnMgO heterojunction self-powered detector had a response half-width of only 14 nm,a peak responsivity of 196 m A/W at 0 V,and a very fast response speed(<3.3 ms),its comprehensive performance is at the leading level among similar devices.