Research And Fabrication Of Wide Band Gap Semiconductor Devices And Measurement Technology

The works in this thesis include research on the UV detector based on wide band gap semiconductor material SiC and ZnO,and research on a high impedance 4-point probe instrument.Details on the nature,materials and devices of the research of the wide band gap semiconductor materials ZnO and SiC,introduced the application in the ultraviolet detector of the two material,and focuses on four different structure of the ultraviolet detector process technology,â… -â…¤characteristics,spectral response characteristics,and spectral response with temperature and voltage changes.Finally introduced a high impedance 4-point probe instrument that we designed based on a high-precision current source,the hardware circuit and the software procedure were given.There are increasing emphases focused on ZnO,a new kind of wide band gap (WBG)semiconductor material with high exciton binding energy,high chemical and temperature stabilization.ZnO thin film has been used widely in gas sensors,solar cells,UV detector and UV blue photo LED,LDS.Meanwhile SiC is another excellent WBG semiconductor.It has a lot of good electrical and thermal properties,such as wide band gap,high breakdown field,high thermal conductivity and high saturation electron velocity.These properties make SiC a preferred semiconductor for the fabrication of devices in high temperature,high frequency,high voltage and high power conditions.For some higher required devices, SiC has replaced the traditional Si and become an international hot spot on one of the new study.The main research works and conclusions are as follows:1)Research of Au/n-ZnO/Au MSM structure UV enhanced photodetectorIntroduced the technics of the device,focuses on the deviceâ… -â…¤characteristics and photo current response.The experiments shown that the spectral response wavelength range of this device is from 200nm UV-band to visible light,it has the conditions for making UV detectors.When working in more than 4V bias voltage,the node capacitance is less than 3pF,making it possible to be used for high-frequency condition.2)Research of Au/n-4H-SiC schottky UV detectorIntroduced the technics of the device,focuses on analyzing the device's spectral response with the bias voltage and temperature changes.The experiments shown that the device remain goodâ… -â…¤characteristics and spectral response characteristics even in high-temperature,high pressure under the limit.The spectral response wavelength range is from 200nm to 400nm,the spectral response sensitivity increases in anti-bias condition,good UV response is still maintained when the temperature is higher than 260℃.3)Research of Au/n-ZnO/p-Si structure UV-enhanced phototransistorFabrication and characteristics of Schottky-emitter heterojunction-collector UV-enhanced bipolar phototransistor(SHBT)are presented.The deviceâ… -â…¤characteristics and photo spectrum response have been tested.The experiments shown that The sensitivity of ultraviolet response from 200nm to 400nm has been enhanced evidently and the wavelength spectrum response of longer than 400nm that is the response wavelength range of traditional Si photo-detector also retained,the UV response sensitivity at 370nm of phototransistor is about 5 times than ZnO/Si hetero-junction UV enhanced photodiode4)Research of Au/n-ZnO/p-SiC structure UV detectorTest and theoretical analysis has been done about the device characteristics ofâ… -â…¤and photo spectrum response of this structure device.The experiments shown that this structure UV detector has a good response of ultraviolet and low reverse leakage current and low node capacitance.The spectral response wavelength range of this device is from 200 to 400nm with peak value at 313nm,and the half width of response wavelength is 65nm.At room temperature,the reverse working voltage is greater than 5V,and the reverse breakdown voltage is 70V.5)Develop of high impedance 4-point probe instrumentIn the light of the wide band gap semiconductor materials resistivity measurement needs,we developed a high-impedance 4-point probe instrument based on a precision current source circuit,the hardware circuit and software processes is given.The current source output range if from 1nA to 100mA,the minimum output current resolution is 0.5pA and maximal output voltage is 200V.The voltage measurement module input range if from 20mV to 2V and the input impedance up to 10¹³Î©.