Preparation And Performance Study Of Magnesium Gallium Doped Zinc Oxide Phototransistor

In recent years,wide bandgap semiconductor materials have attracted widespread attention from researchers in the preparation and application of optoelectronic devices.Among them,zinc oxide（Zn O）,as a multi-functional semiconductor material,is widely used for the preparation and application of various optoelectronic devices due to its many advantages,such as high transmittance,thermochemical stability,excellent piezoelectricity,low cost,high mobility,low-temperature processing,etc.in the visible light range.Based on these advantages,zinc oxide is widely used in the preparation of optoelectronic devices.However,with the gradual development of transistor technology,there are various defects in pure zinc oxide based phototransistors,which can make it difficult for the mobility,responsiveness,and other parameters of the device to meet various needs,limiting its further development.Through research,it has been found that doping appropriate metal ions into zinc oxide can improve the performance of phototransistors.In this study,magnesium gallium doped zinc oxide（MGZO）films were deposited by radio frequency Magnetron sputtering equipment,used as the active layer,thermal silicon dioxide（Si O2）as the gate insulation layer,metal aluminum（Al）as the source and drain electrode to prepare the phototransistor devices.To investigate the effects of changing growth parameters（active layer thickness,sputtering pressure,electrode structure）during thin film deposition on the electrical,optical,UV detection properties of MGZO thin films and phototransistor devices,the main research contents are as follows:1.The MGZO films with different active layer thicknesses were prepared by RF magnetron sputtering equipment at room temperature by controlling the deposition time of the films and the bottom gate top contact phototransistor devices with traditional electrode structure were fabricated.The thickness,optical properties,and surface morphology of the thin film were characterized,the influence of active layer thickness on various performance aspects of the thin film and device was analyzed.In this experimental group,when the thickness of the active layer is 40nm,the deposition quality of the thin film is the best,the overall performance of the device is the best:switching current ratio I_on/off=5.28×10⁷,subthreshold swing SS=0.926V·dec^-1,threshold voltage V_th=1.0V,mobilityμ_FE=8.67cm²·V^-1s^-1.This is mainly because the thickness of the film is related to the probability of reflection of the crystal surface during carrier transmission,as well as the electron capture condition in the film and other defects,resulting in the reduction of the comprehensive performance of devices made of films of other thicknesses.2.MGZO thin films were prepared by RF magnetron sputtering equipment at different growth temperatures,the bottom gate top contact phototransistor devices with traditional electrode structure were fabricated.The optical properties and surface morphology of the thin film were characterized,the influence of growth temperature on various aspects of the film and device performance was analyzed.The results show that when the growth temperature is 60℃,the deposition quality of the thin film is the best,and the overall performance of the device is the best,the overall performance of the device is the best:switching current ratio I_on/off=2.27×10⁷,subthreshold swing SS=1.219V·dec^-1,threshold voltage V_th=0.63V,mobilityμ_FE=1.97cm²·V^-1s^-1.The main reason for this is that there are differences in the number of oxygen vacancies in the thin film the activity of target atoms and gas ions at different temperatures,the high activity of target atoms and gas ions is the reason for the reduced performance of the device.3.MGZO thin films were deposited using radio frequency magnetron sputtering equipment at different sputtering pressures at room temperature,and bottom gate top contact phototransistor devices with traditional electrode structure and MSM interdigital electrode structure were fabricated.The optical properties and surface morphology of the thin films were characterized,and the effects of sputtering pressure on the performance of the thin films and devices in various aspects were studied.In this experimental group,when the sputtering pressure is 10m Torr,the deposition quality of the thin film is the best,the overall performance of the device is the best:the switching current ratios of traditional electrode structure and MSM interdigital electrode structure are I_on/off=2.35×10⁷,2.89×10⁷,the sub threshold swing are SS=1.270V·dec^-1,0.955V·dec^-1,the threshold voltage are V_th=2.49V,-0.98V,the mobility areμ_FE=2.51cm²·V^-1s^-1,9.25cm²·V^-1s^-1.This is mainly due to the influence of sputtering pressure on the ionization degree of argon gas,target atomic energy and oxygen vacancies.When the sputtering pressure is low,there are more oxygen vacancies in the film;When the sputtering pressure is high,the probability of scattering of target atoms increases,the density of internal defects and interface trap states increases.All of these will reduce the overall performance of the device.At the same time,a comparative analysis was conducted on the electrical performance of MSM interdigital electrode structure devices under dark conditions and 365nm ultraviolet light irradiation.The results showed that the highest response was42.88A/W at 10m Torr,the response time was 7.7 seconds.