Preparation And Performance Of Ultraviolet Detectors Based On Sb,Sn And Zn-doped β-Ga₂O₃ Microstructures

Gallium oxide is a direct band gap semiconductor material with an ultra-wide band gap of 4.9 e V,which corresponds to the solar blind ultraviolet band.Moreover,it is highly transparent to visible light and has good electrical and optical properties,and the maximum breakdown electric field is 8 MV/cm.β-Ga₂O₃is an ideal material for making high-power electronic devices and solar blind UV detection,the devices have been widely used in the fields of ozone layer monitoring,environmental detection and safe communication.Because the undopedβ-Ga₂O₃material is n-type and has poor conductivity,it is usually necessary to doping it to improve the conductivity ofβ-Ga₂O₃,and the preparation of p-typeβ-Ga₂O₃is more difficult.In order to solve the above problems,we used CVD technology to grow Sb dopedβ-Ga₂O₃microbelts and Sn dopedβ-Ga₂O₃microwires respectively,and the ultraviolet detection characteristics of the Sb and Sn-dopedβ-Ga₂O₃microstructures were studied.In addition,Zn-dopedβ-Ga₂O₃thin film was grown on the mechanically stripped n-typeβ-Ga₂O₃single crystal microsheet by CVD method to make a homojunction UV detector,and the ultraviolet detection performance of the device was explored.The main research contents of the thesis are as follows:（1）Using CVD method,first grow a layer of Sb-dopedβ-Ga₂O₃seed layer on sapphire substrate,and then the Sb-dopedβ-Ga₂O₃microbelts was grown on the seed layer.It is found that the seed layer plays a decisive role in the growth of microbelts,which are about 10μm in diameter and 150μm in length and have good crystal quality.In addition,the MSM photoconductive UV detector was fabricated based on the Sb dopedβ-Ga₂O₃microbelts.It was found that the light-dark current ratio of the device reached 1.67×10~3at 10 V.The rise time of the device is 0.12 s,and the fall time is 0.04 s.When the optical power density is 100μW/cm~2,the responsivity of the device is 0.8 A/W,and the external quantum efficiency is390%.（2）Theβ-Ga₂O₃single crystal microsheets were stripped fromβ-Ga₂O₃single crystal substrates by mechanical stripping method,and Zn dopedβ-Ga₂O₃thin films were grown on microsheets by CVD.Through characterization,we found that the surface of Zn-dopedβ-Ga₂O₃films is flat and compact,and the crystal quality is good.The UV detector test of Zn-dopedβ-Ga₂O₃/n-typeβ-Ga₂O₃homojunction device shows that the device has good rectifying characteristics and self-powered performance.At zero bias,the responsivity of the device is up to 1.24 A/W,with good repeatability and stability over multiple switching cycles.The rise time of the device is 0.18 s,and the fall time is 0.14 s.The successful preparation of the device provides a feasible method for the development ofβ-Ga₂O₃homojunction UV detector.（3）A large number of Sn-dopedβ-Ga₂O₃microwires were grown in the corundum boat by CVD method.The microwires were up to 7 mm in length and about 20μm in diameter.The singleβ-Ga₂O₃microwire was selected,the metal Pt was evaporated at one end,and a Schottky junction solar-blind UV detector was prepared.The results show that a good rectifying characteristic is formed between Pt and Sn dopedβ-Ga₂O₃microwires.Moreover,the device has strong sensitivity to 254 nm ultraviolet light.At 0 V bias,the responsivity of the device is 0.44 A/W and the external quantum efficiency（EQE）is 215%.