Design And Fabrication Of Silicon-based Germanium Infrared Photodetector Devices

In recent years,optoelectronic technology has developed rapidly;optoelectronic devices based on group IV semiconductor materials are widely used in optoelectronic integration and high-speed optical communication,they are also considered to be the high-quality choice for infrared photodetectors.However,Si and Geof group IV belong to indirect bandgap semiconductors,and the electron transition efficiency is low,which limits the application of Si and Gein the field of optics.The GeSn alloy semiconductors formed by doping Sn into Gecan be converted into direct band gaps with tunable band gaps,which makes the photodetectors prepared from GeSn materials have great prospects in infrared light detection.In this thesis,the GeSn and GeBi films in germanium-based semiconductors grown by MBE are used,then optimized by the microstructure of the film and the device structure.Therefore,a germanium-based PIN infrared photodetector and2×2 optoelectronic array are prepared based on the film analysis and simulation optimization.And the main work and results of this thesis are as follows:(1)GeSn and GeBi films at different growth temperatures were prepared by MBE.The Sn content of the GeSn film was 15.72 %?22.34 %,and the Bi content of the GeBi film was 4.32 %?13.39 %.Then,the microstructure of the film was studied and analyzed by using XRD and AFM.it can be seen that the GeSn with Sn content of16.81 % and the GeBi film with Bi content of 8.72 % prepared at the growth temperature of Sn source of 1000 ? and Bi source of 450 ? have good performance.The film has excellent quality without the phenomenon of Sn and Bi precipitation,the film has high infrared absorption efficiency.(2)Based on Sentaurus simulation software,the photoelectric characteristics of germanium-based PIN photodetector were simulated and analyzed.The effects of the thicknesses of P,I and N layers and the doping concentrations of P and N layers on the quantum efficiency,responsivity and volt-ampere characteristics of the PIN photodetector were studied and analyzed.Simulation studies show that each layer of the device has a positive correlation with the optoelectronic performance.The quantum efficiency,responsivity and photocurrent increase with the increase of thickness.The increase in the thickness of the P and N layers can also shift the detection range of the device to the long-wavelength direction,but the actual thickness cannot be increased infinitely,and the increase of the doping concentration of the N and P layers can be increased to a certain extent.Reduce the dark current of the device,thereby increasing its light-dark current ratio.The actual design of the device structure should comprehensively consider the appropriate thickness and doping concentration.(3)Based on the structural parameters obtained from thin film analysis and device simulation,silicon-based germanium photodetectors with different thicknesses of P and N layers were prepared when the thickness of the I layer was 120 nm.The influence of photo-dark current,which reflects the volt-ampere characteristics and opto-electronic characteristics of the correct device structure,was tested.It is found that the effect of thickness is consistent with the simulation results.The dark current of the prepared photodetector device is in the range of 0 V bias voltage;the maximum photocurrent is393.6 n A,and the maximum light-dark current ratio is 398.2×2 optoelectronic arrays with different light-passing window sizes were prepared based on the device unit parameters with the largest light-dark current ratio,and the consistency and stability of their optoelectronic properties and the performance of the array unit device were tested.The performance of the array unit fluctuates in the range of about 10%,and the optoelectronic array with high consistency is obtained.2×2 photoelectric array with high consistency.