Research On Silicon-Based PbSe Photodetector With Light-Trapping Structure

Silicon-based photodetectors,with mature preparation technology and excellent photoelectric performance,are widely used in national defense,industry and civil and other fields.However,traditional silicon-based photodetectors have limited detection wavelength range and weak photoelectric response to near-infrared light.Therefore,The integrated light limiting structure can enhance the light absorption of the device,and broaden the response band by combining with other narrow band gap semiconductor materials.Lead Selenide(PbSe)is a common compound of groupⅣ-Ⅵ,and the band gap of bulk materials is 0.28 e V at normal temperature and pressure,which is an ideal semiconductor material used for infrared photoelectric detection.Based on PbSe material,silicon-based PbSe thin film and quantum dot photodetectors with integrated light-limiting structure were prepared and researched in this thesis.The optical simulation of the devices with integrated light-limiting structure is carried out through the finite difference time domain(FDTD)simulation software,The influences of micropore diameter,period and substrate on the light limiting effect of micropore structure were investigated,the light absorption rate and electric field intensity distribution of the device were calculated and analyzed.The simulation results show that the light-trapping ability of the micropore structure is closely related to the micropore size,when the micropore diameter/period is 700/1000 nm,the light absorption rate of the device is the highest and the photoelectric performance is the best.Moreover,the influence of the working voltage and electrode spacing on the electric field distribution in the device was simulated by the finite element drift-diffusion simulation software Lumerical CHARGE(CHARGE).The simulation results show that increasing the working voltage and decreasing the electrode spacing can deepen the electric field depth.PbSe thin films were prepared by vacuum evaporation method with low surface roughness and small crystal particles.The microporous structures and interfinger electrodes were prepared on the surface of the thin films by semiconductor processes such as photolithography,etching and sputtering.The device can detect the incident light at405～1550 nm band,The cutoff wavelength of the silicon-based detector is broadened effectively,and the optical limiting structure significantly improves the photoelectric performance of the device.The device has a maximum responsitivity of 0.285 A/W at1550 nm,a specific detectivity of 4.195×10~9Jones,and a minimum response time of48.49μs.PbSe quantum dots with stable properties were prepared by thermal injection method,the diameter of the dots is about 6.28 nm,and the first exciton absorption peak is at 1732nm,and the calculated band gap of the dots is about 0.695 e V.Then,PbSe quantum dot solution was spun on the surface of the device with light-trapping structure.Test shows that the device has wide spectral response characteristics,the quantum dot brings gain to the inside of the device,and the microporous structure improves the photoelectric responsitivity of the device.At 1550 nm,the device has a maximum responsitivity of 1.93A/W,a specific detectivity of 2.227×10~9Jones,the response time at 850 nm wavelength is 8.67μs.