Researches On Suppression Of Persistent Photoconductivity In Gallium Oxide Film Photodetectors

Ga2O3 has the advantages of a wide band-gap（about 4.8 e V）,high light absorption coefficient,good thermal and chemical stability,strong resistance to radiation,and low cost.Ga2O3 is one of the hotspot materials used in the fabrication of solar-blind ultraviolet detectors in recent years.Introducing an appropriate amount of Vo in Ga2O3 can produce an intermediate energy level in the band-gap of Ga2O3,so that the Ga2O3 is provided with ultraviolet-visible wide-band detection capabilities.However,there is a contradictory relationship between the responsivity and the response recovery speed of the photoconductive and the Schottky Ga2O3 photodetector.The reason is that defect-related photoconductivity gain and persistent photoconductivity increase responsivity and prolong response recovery time,respectively.In addition,the formation mechanism of photoconductive gain and persistent photoconductivity still needs further clarification.This thesis focuses on the Ga2O3photodetectors with high responsivity and fast response recovery speed,and conducts research on annealing control defects,and applying"interference"to suppress persistent photoconductivity.High performance Ga2O3 photodetectors were prepared.Explore the mechanism of photoconductive gain and persistent photoconductivity in Ga2O3photodetectors.The main results are as follows:1.The effect of annealing on the performance of Ga2O3 film Schottky photodetectors.In order to clarify the interaction between the defects and the photons and the carriers,and its effect on photoconductive gain and persistent photoconductivity,we annealed the amorphous Ga2O3 containing a large amount of Vo in an oxygen atmosphere.The effects of annealing temperature on the concentration of Vo were studied.The results show that as the annealing temperature increases from 500 ^oC to 800 ^oC,the Vo concentration in Ga2O3 gradually decreases,and the photoconductive gain of the back to back Schottky Ga2O3 photodetector gradually decreases,while the persistent photoconductivity effect gradually diminily.The Vo transition to long-lived Vo²⁺is the main mechanism that leads to the photoconductive gain and persistent photoconductivity.When the annealing temperature of Ga2O3 is 650 ^oC,the Ga2O3photodetector has a relatively high responsivity（60 m A/W）and a faster response recovery speed（0.14 s）.2.Thermal interference suppresses the persistent photoconductivity of the Ga2O3 film photoconductive photodetectors.We have been inspired by the former person’s stress field to suppress persistent photoconductivity,and we studied the inhibitory effect of thermal on the persistent photoconductivity in the Ga2O3 photoconductors by rapid heating and cooling.After the rapid room temperature to 120 ^oC to room temperature,the response recovery time of the device is reduced from a few hours to a few seconds without affecting the high responsivity（1099 A/W）of the device.We studied the effect of heating time and cooling time and heating temperature on the dark current of the device.It is found that the appropriate extension heating time and appropriate increase heating temperatures are advantageous for obtaining lower dark currents.The effect of thermal interference is mainly attributed to thermally stimulating electrons in the conduction band tail state to enter the conduction band,increasing the free electron concentration and increasing the neutralization probability of electrons and V_o²⁺.3.Electric field interference suppresses the persistent photoconductivity of the Ga2O3film Schottky photodetectors.We study the effect of pulse voltage on persistent photoconductivity in back to back Schottky,unidirectional Schottky and photoconductive photodetectors.On the reverse biased Schottky junction,a forward pulse voltage of different size and width is applied,and the dependence of the inhibitory effect of persistent photoconductivity and the pulse size and width is studied.Analysis shows that the gain and persistent photoconductivity mechanism in our reverse-biased Schottky junction devices do not strictly follow the interface state trapping holes and hole self-trapping models,but are mainly attributed to the long-lived Vo²⁺in the Schottky junction.These Vo²⁺caused mirroring force and tunneling effect,which reduces the height of the effective Schottky barrier.During the application of the forward pulse voltage,the width of the Schottky junction is reduced,and the carrier concentration near the Schottky junction changes,promoting the neutralization of electrons and the Vo²⁺.The height of the effective Schottky barrier is restored,thereby suppressing persistent photoconductivity.Finally,we have obtained a Schottky Ga2O3photodetector with high responsivity（>2.5 A/W）and a response recovery time of hundreds of milliseconds.