Research On Silicon Based Wide Spectrum Photodetectors

With the development of photoelectric detection technology,photoelectric detection technology is widely used in radar,communication,guidance,temperature measurement,positioning,scientific research and other fields.However,for wide spectrum detection,the combination of multiple photodetectors is still required,and the device integration is low and the operation method is complex.At present,the silicon-based semiconductor process is mature and stable,which can be used for large-scale,low-cost chip production.Designing a silicon based wide spectrum photodetector will have a wide application prospect.In this paper,two kinds of semiconductor materials,ZnO and Ga₂O₃,are used to form a multilayer structure with Si substrate,and the response spectrum of Si based photodetector is expanded to the deep ultraviolet region,and the silicon-based wide spectrum photodetector with response spectrum covering the UV-visible-near-infrared region is developed。The main results of this paper are as follows:1.ZnO thin films were grown on（111）Si substrate by RF reactive magnetron sputtering technology,and the effects of substrate temperature and gas flow ratio on the growth quality of ZnO thin films were studied.The optimized process parameters were as follows:substrate temperature 300°C,O₂:Ar flow ratio 1:2,total gas flow rate 30 sccm,sputter power 150 W,and working pressure 1 Pa.The XRDθ-2θdiffraction peak FWHM of（002）crystal plane is 0.63°.The average grain size L_calong the c axis is about 12.86 nm according to Scherrer’s formula.According to UV-VIS absorption spectrum and Tauc formula,it is proved that the absorption edge of ZnO thin film is about 365 nm,and its optical band gap is about 3.40 e V.2.Based on the optimized ZnO growth process,the metal-semiconductor-metal（MSM）structure ZnO/Si wide spectrum photodetectors and the buried MSM electrode structure ZnO/Si wide spectrum photodetectors were fabricated,and the effects of the device structure and the band structure on the device performance were analyzed.The ZnO ultraviolet light absorbing layer effectively broadens the spectral response width of the Si photodetector.The ZnO/Si wide spectrum photodetector with buried MSM electrode structure has a responsivity greater than 1.6 A/W in the range of 365 to 980 nm under a 5 V bias.The highest responsivity was obtained at the incident light wavelength of 808 nm,with a responsivity of 14.2 A/W.The buried electrode structure directly absorbs the photogenerated charge carriers generated in ZnO and Si,reduces the leakage electric field in the air,increases the effective collection area of charge carriers,and improves the collection efficiency of photogenerated charge carriers.3.Rf reactive magnetron sputtering technology was used to sputter Ga₂O₃ceramic target,and the ZnO film grown on（111）Si was used as the substrate to grow Ga₂O₃ film.We characterized the film,proved that the grown Ga₂O₃ film is amorphous film,and tested its optical properties.The optical band gap of Ga₂O₃ film is about 4.64 e V,and the absorption edge is about 267 nm.It has good absorption of deep ultraviolet light.Then we used this Ga₂O₃ film to fabricate Ga₂O₃ photodetectors and Ga₂O₃/ZnO/Si wide spectrum photodetectors.The Ga₂O₃ deep ultraviolet light absorption layer further broadens the spectral response width of the Si photodetector.The wide spectrum Ga₂O₃/ZnO/Si photodetector has responsivity greater than 1 A/W from 254 nm to 980nm at 5V bias.The highest responsivity is 8.27 A/W when the incident light wavelength is 365 nm,and 4.87 A/W when the incident light wavelength is 254 nm.