Optoelectronic Properties Of Ga₂O₃/ZnO Thin-film Ultraviolet Photodetectors

In recent years,UV photodetectors have been widely concerned at home and abroad due to their applications in both military and civil fields,and have become a research hotspot at present.At present,the material used for the preparation of UV photoelectric detectors is mainly the direct bandgap broadband semiconductor material ZnO.However,but due to the inherent defects of ZnO UV detectors,such as the high dark current and slow response speed,the detector has not been able to meet the requirements.Since Ga₂O₃ material has excellent properties such as high electron mobility and diffusion coefficient,ZnO material has stable photoelectric conversion ability,and the crystal structure and atomic spacing of Ga₂O₃ and ZnO are similar,therefore,by combining these two materials to prepare a new MSM structure of Ga₂O₃/ZnO UV photodetector,which can greatly improve the responsiveness and response speed of the photodetector.This kind of photodetector will enable them to have a broader scope for development in the fields of energy saving and carbon reduction,information technology and national defense and security.In this paper,we focued on the effects of different preparation methods and process conditions on the optoelectronic properties of new Ga₂O₃/ZnO thin film UV detectors with MSM structure,in order to produce UV detectors with the properties both high responsiveness and faster response time.The main findings and conclusions are as follows:（1）In this paper,the effects of different compounding methods on the crystalline quality,surface morphology,and UV-vis spectra of Ga₂O₃/ZnO thin films were investigated by using the sol-gel method.It is found that the forbidden band width can be adjusted from 3.59 to 5.13e V by changing the combination of ZnO thin films and Ga₂O₃ thin films;the structure and spectral properties of S2-Ga₂O₃/ZnO composite films prepared by stepwise post-annealing treatment are better than those of S1-Ga₂O₃/ZnO films prepared by one-step post-annealing treatment.The results provide a good foundation for the subsequent study of Ga₂O₃/ZnO thin film UV detectors.（2）In this paper,the effects of different compounding methods,thickness of each functional layer,post-annealing temperature,and applied bias voltage on the performance of Ga₂O₃/ZnO thin-film UV detectors with MSM structure were systematically investigated by using the controlled variable method.It is found that,by optimizing the process parameters of Ga₂O₃/ZnO thin-film UV detector,the tested properties of the detector under a bias voltage of 20 V are as follows:the ratio of photodark/current of the detector reached 253.83,the responsiveness reached19.29 A/W,the detection rate reached 7.14×10¹²Jones,and the rise/fall time reached 1.56s/2.85s.It is shown that optimization of the Ga₂O₃/ZnO thin film preparation process can effectively improve the responsiveness and speed of the detector by reducing the dark current.（3）Based on the local surface resonance effect of metal-nano plasma,a new MSM structure of Al-NPs/Ga₂O₃/ZnO thin film UV detector was prepared.It is found that the wavelength of strongest local electric field intensity of metallic Al-NPs is 254 nm with the optimum radius of Ag-NPs is 30 nm.Under a bias voltage of 20 V,moreover the photo/dark current ratio of the Al-NPs/Ga₂O₃/ZnO device increased by a factor of 4.4,the responsiveness increased by a factor of3.2,and the detection rate increased by a factor of 3.6.This study provides an effective method for the preparation of new UV detectors with both high responsiveness and faster response rates.