| There is no solar-blind UV light which is absorbed by the ozone layer near the ground,therefore,with less influence by the external environment,solar-blind photodetectors have attracted increasing attention due to a wide range of applications in monitoring missile,fire,ozone hole detection,and ultraviolet communications.Ga2O3,the third generation semiconductor with 4.8-5.3 e V band gap width,is very suitable for the application in the field of solar-blind detection,because of its simple preparation process and stable physical and chemical properties.Compared with crystalline Ga2O3 thin film detectors,amorphous Ga2O3（a-Ga2O3）thin film detectors have the advantages of both high responsivity and fast response recovery speed.Besides,low temperature preparation is conducive to its application in the field of flexibility.In addition to material selection,device structure design is also an effective way to improve detector performance.This thesis,selecting a-Ga2O3 thin film as the detection material,tries to focus on the innovative design of the device structure to improve the detector performance and analyze the internal gain mechanism of the detector.（1）The a-Ga2O3 films with different thickness are deposited on glass substrates with SnO2:F films（FTO）by means of magnetron sputtering to prepare the FTO/a-Ga2O3 vertical structure solar-blind photodetector.The devices exhibit heterojunction characteristics.Due to the high FTO carrier concentration,the device has a large photocurrent and can work at low voltage.The device has the best overall performance,with the photocurrent reaching 4.06×10-4 A under-2 V bias,and the responsivity reaching 508.7 A/W,when the thickness of a-Ga2O3 film is 595 nm.The disadvantage of the device is that the dark current is large while the light dark current is small,which results from the high FTO carrier concentration.（2）The magnetron sputtering method is also used to deposit Zn O:Al（AZO）thin film and a-Ga2O3 thin film on sapphire substrate successively to prepare AZO/a-Ga2O3vertical structure solar-blind photodetector,to study the effect of different thickness AZO films on device performance and the internal gain mechanism of the device.Compared with the FTO film,the carrier concentration of the AZO film is much reduced.The analysis shows that the device has a Zener tunneling internal gain mechanism,and its overall performance is improved.AZO（100 nm）/a-Ga2O3（800 nm）device has the best comprehensive performance.Its dark current is 1.14×10-8 A,photo-dark current ratio reaches 2.2×103,and responsivity reaches 67.26 A/W.The response speed is so fast,with rise time researching 1.53μs and the decay time being 2.25/50.4ms.In addition,the device has a significant self-powered effect.At 0 V bias,the device’s photo-dark current ratio can reach a maximum of 183.3,and the responsivity reaches2.92×10-2 A/W.（3）The a-Ga2O3 thin films grow on the SiO2/Si++substrates,and obtain phototransistor solar-blind detectors.Negative gate voltage can suppress dark current,meanwhile,the device combines the internal gain of a-Ga2O3 thin film material and the intrinsic gain of the transistor,resulting in a large photocurrent and responsivity of the device,so the device can have excellent overall performance.When the a-Ga2O3 film is 51 nm,the dark current of the device at-20 V gate voltage is 5.76×10-9 A and the larger internal gain researches G=6.79×103,which results in an increase in photocurrent and the responsivity reaches 942 A/W.The improvement of the parameters above makes the device have a larger photo-dark current ratio and detection rate,respectively6.23×104 and D*=1.07×1015 cm·Hz1/2·W-1. |
PDF Full Text Request