Research On Performance Improvement Of Silicon-based Photodetectors And Their Application In Terahertz

The rapid development of the mobile Internet and the explosive growth of data capacity pose new challenges to the transmission,storage,exchange and processing of information.Optical fiber communication technology carries more than 90% of the information transmission capacity because of its advantages of large bandwidth and low loss.However,the demand for large-capacity transmission requires a larger-capacity optical fiber transmission system.On the other hand,wireless broadband access technology is also a hot spot in the industry and academia.In the next-generation wireless communication system,the carrier frequency may be increased to the terahertz(THz)band.The silicon-based photonic integrated system has the potential advantage of using large-scale production to reduce costs,and it has been the focus of international research in recent years.Research on the performance improvement of silicon-based photodetectors is of great significance to the development of large-capacity silicon-based integrated optical fiber communication technology and the realization of THz transmission and reception.The thesis has carried out theoretical and experimental research on the performance improvement of the silicon-based photodetector and its application in THz technology.The representative research results are listed as follows:(1)The simulation model of the silicon germanium(Si-Ge)photodetector is constructed,and the simulation method of the doping condition of the active region of the detector is analyzed.The simulation results obtained by the constructed optical and electrical simulation model are in good agreement with the experimental results.The accuracy of the simulation model lays the foundation for the subsequent device design of the Si-Ge photodetector.(2)The method to improve the bandwidth and robustness of the silicon-based germanium avalanche photodetector(Ge APD)is studied.A solution is proposed to use the dual intrinsic region structure to enhance the peak effect of the inductive gain inside the device and further increase the bandwidth of the device.In this scheme,photo-generated carriers utilize the impact ionization effect in the intrinsic region of Ge to achieve avalanche multiplication,and photo-generated holes exploit the impact ionization effect in the intrinsic region of silicon to enhance the equivalent inductance.Simultaneously,the added silicon intrinsic region can withstand a higher bias voltage to improve the robustness of the device.The silicon-based Ge APD has a maximum gain of 14 and a gain-bandwidth product of182 GHz.While working at a high reverse bias of 10.5 V,it still has a large bandwidth of24.3 GHz,and the error-free sensitivity at 20 Gbit/s is improved by 6.1 d B compared to the no gain state.(3)The method to increase the saturated output power of the Si-Ge photodetector is investigated.A scheme based on doping control is proposed,which is manufactured by optimizing the concentration of the doped region of the device and using conventional processes.It utilizes the saturation characteristic that the concentration of photo-generated carriers cannot exceed the doping concentration of the adjacent collection layer.Compared with other Si-Ge photodetectors,the saturation photocurrent performance is improved by nearly 85.7%,the maximum saturation photocurrent density reaches 1.82 m A/μm3,and the-1 d B suppression current at 5 GHz rate also shows a 57% improvement.(4)The realization of the THz emission,reception and the THz interconnection between chips by integrating the silicon-based photodetector with a broadband bow-tie THz antenna is studied.On the one hand,based on the high-power Si-Ge photodetector,the THz emitter achieves the THz emission in the range of 10 GHz-1 THz,and it has a maximum radiation power of 8 n W at 100 GHz.The Si-Ge THz receiver achieves THz wave reception in the range of 10-300 GHz and a maximum conversion efficiency of 3.6 μA/W-1/2 at100 GHz.Subsequently,the Si-Ge THz transceivers are used to realize the interconnection between silicon-based chips in the range of 10-100 GHz.On the other hand,a large bandwidth silicon-based plasmonic graphene photodetector integrating with a bow-tie THz antenna achieves THz emission.The emitted THz spectrum in the range of 50-300 GHz is flat,with a maximum radiation power of 5.4 n W at 145 GHz,which explores a new path for the realization of large-bandwidth THz radiation.