Design And Implementation Of PIN-type Germanium Waveguide Photodetector

Photonic integration technology is one of the most popular engineering technologies in recent years.It is an application technology of optical component manufacturing developed on the basis of modern integrated optics.Photonic integrated devices can be divided into different device types according to different functions,such as lasers,modulators,passive couplers,etc.Among a large number of semiconductor materials,strain Si,Si Ge and Ge materials are the new generation of silicon-based materials developed in recent years.High-performance photodetectors should be characterized by high responsiveness and low dark current in response bands.Because germanium has a high absorption coefficient in its optical communication band and high electron and hole mobility in near-infrared band,germanium based optoelectronic devices have attracted extensive attention in recent years.At the same time relative to the ?-? semiconductor,germanium material compatible with silicon microelectronic technology,has become the best choice of the silicon substrate integrated photodetector.Germanium waveguide photodetector as the interface of photoelectric conversion in the integrated circuit and "terminator" of photons in the optical path is of great significance for silicon photonic integration.The research in this thesis lays a good foundation for the synthesis of high performance detector array and the integration of array waveguide grating demodulation system.In this thesis,our main research contents are as follows:(1)By studying the theoretical basis and performance parameters of pin-type germanium waveguide photodetector,the excitation of light absorption and photogenic carriers was analyzed,including intrinsic absorption,exciton absorption,impurity absorption and free carrier absorption,so as to study the transport mode of photogenic carriers,including diffusion and drift processes.Based on the analysis and calculation of the relationship between the thickness and area of the active region of the Si based Ge photodetector and the 3d B bandwidth of the device,an ideal detector structure is proposed based on the calculation,and the methods and means to improve the performance of the photodetector are proposed based on the actual experimental conditions and other comprehensive factors.The influence of size,waveguide on structure and doping concentration on the performance of PIN type Si-based Ge photodetector is analyzed.(2)This thesis presents a high efficiency and low dark current germanium waveguide photodetector with longitudinal PIN structure.Based on the in-depth analysis of the photogenic carrier collection process in the detector and the relationship between quantum efficiency,dark current and capacitance performance and device structure,the carrier collection enhancement structure is analyzed.By studying the dark current,capacitance,quantum efficiency and other performance parameters of photodetectors,the problem of improving the collection efficiency of photogenic carriers and reducing the surface recombination of photogenic carriers is solved.The length and thickness of the germanium waveguide are analyzed and calculated by studying the photon energy,the relationship between absorption coefficient and extinction coefficient,and the absorption limit wavelength of germanium materials.Through the analysis of the dark current theory and experimental data,the source of the dark current of the device was found,and the structure of the PIN photodetector was further optimized.The research in this thesis will promote the miniaturization of fiber grating demodulation system and lay a foundation for the further development of silicon-based photonic integration technology.