Study On The Effect Of NF₃ Atmosphere Thermal Annealing On The Photoelectric Properties Of Ga₂O₃ Films

Gallium oxide（Ga₂O₃）,as an ultra-wide-band oxide semiconductor with a band gap of about 4.9 e V,is an important material in the field of deep ultraviolet photoelectrodetection.Due to the high growth temperature of Ga₂O₃ films,a large number of intrinsic defects in the films reduce the carrier transmission and separation efficiency,which directly affects the performance improvement of Ga₂O₃ based photodetectors.Gallium oxide（Ga₂O₃）,as an ultra-wide-band oxide semiconductor with a band gap of about 4.9e V,is an important material in the field of deep ultraviolet photoelectrodetection.Due to the high growth temperature of Ga₂O₃ films,a large number of intrinsic defects in the films reduce the carrier transmission and separation efficiency,which directly affects the performance improvement of Ga₂O₃based photodetectors.At present,the main methods to improve the photoelectric properties of Ga₂O₃ materials are:high temperature oxygen annealing to reduce the defect density and cationic doping to improve the conductivity of thin films.However,the above two methods have some limitations,so it is necessary to explore a new method to regulate the photoelectric properties of Ga₂O₃.In this paper,a method of regulating the photoelectric properties of Ga₂O₃ thin films by nitrogen trifluoride（NF₃）atmosphere thermal annealing is proposed..The photoelectric properties of polycrystalline and amorphous Ga₂O₃ thin films vary with the concentration of NF₃ gas and annealing temperature,and the doping and passivation mechanisms of N and F are discussed.At the same time,the effect of annealing in NF₃atmosphere on the performance of Ga₂O₃ thin films metal-semiconductor-metal（MSM）photodetectors was studied.Specific research contents are as follows:（1）Effect of annealing temperature in NF₃ atmosphere on photoelectric and optical detection properties of Ga₂O₃ films.Ga₂O₃ polycrystalline films were annealed at different temperatures（330℃-330℃）in a tubular furnace under constant NF₃ gas concentration.Scanning electron microscopy（SEM）,photoemission spectroscopy（PL）and atomic force microscopy（AFM）were used to study the variation of surface roughness,defect luminescence and work function of thin films with annealing temperature..The SEM results show that NF₃ gas has no obvious etching effect on the film at 330℃,and the etching intensifies with the increase of temperature.The PL results showed that the luminescence intensity of defects related to oxygen vacancy decreased gradually with the increase of annealing temperature,which proved that NF₃ atmosphere hot annealing had a certain passivation effect on oxygen vacancy.The results of AFM surface potential test show that the work function of Ga₂O₃ increases with the increase of annealing temperature,indicating that the carrier concentration of the film decreases.MSM light detector was prepared based on Ga₂O₃ thin film.The test results show that the dark current of the device decreases with the increase of annealing temperature,and the response speed increases,while the responsivity decreases.The possible reason is that the N after the decomposition of NF₃ reacts with Ga₂O₃thin film to produce the effect of main doping at 330℃.（2）Effect of atmospheric concentration of NF₃ on photoelectric properties and optical detection of Ga₂O₃ films.The effect of NF₃ concentration（0.27-0.84%）on the photoelectric properties of Ga₂O₃ polycrystalline and amorphous films was investigated by keeping annealing temperature unchanged at 330℃.The variation of surface roughness,defect luminescence and work function of polycrystalline and amorphous films with the concentration of NF₃ were compared by SEM,PL,X-ray photoelectron spectroscopy（XPS）and AFM.SEM and PL results show that the intensity of the deep level luminescence peak related to oxygen vacancy decreases with increasing concentration.XPS and AFM surface potential tests show that F generated by NF₃ decomposition at 330℃can passivate oxygen vacancy defects and replace surface oxygen atoms,thus reducing the surface work function of the film.At the same time,the light-dark suppression ratio,responsivity and detection rate of Ga₂O₃ thin film photodetectors are significantly improved with the increase of NF₃concentration,which also proves that NF₃ atmosphere annealing can play a role in the passivation and donor doping of Ga₂O₃ thin films.