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Large-bandwidth And High-pwer Silicon-based Germanium Photodetector And Its Application

Posted on:2021-12-10Degree:DoctorType:Dissertation
Country:ChinaCandidate:D ZhouFull Text:PDF
GTID:1488306107957359Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Silicon-based photonic integrated chips pave the wave for the development of integrated optical communication systems with their unique advantages.As a bridge between optical and electrical domains,the bandwidth of silicon-based photodetector is a key factor which limits the communication capacity of integrated systems.In addition,with the rapid development of silicon photonics,the application of silicon-based optical integration system extends from the initial digital optical transmission to the microwave analog link,and other characteristics of photodetectors,such as responsivity,dark current and saturation power,are attracting researchers' attention.Therefore,it is a very important issue that how we could optimize the silicon-based photodetector for different application scenarios.At present,the main method to realize the photodetector on the silicon-based integration platform is to introduce the epitaxial germanium layer which is compatible with the CMOS fabrication process.In order to facilitate the large-scale system integration,it is a challenging task to optimize the performance of silicon-based germanium photodetector under the standard fabrication process.This thesis mainly focuses on the silicon-based germanium photodetector.Based on the previous theory,high-performance silicon-based germanium photodetectors are designed and fabricated,including the large-bandwidth,high-responsivity,and high-power cases.These photodetectors are optimized with full consideration of the requirement of application and the design trade-off.With the help of the high-performance silicon-based germanium photodetector,the novel integrated systems applying to on-chip optical interconnects and microwave photonics are performed.The works in this thesis can be summarized as below.(1)The basic theroy of the germanium photodetector is deeply studied.The simulation model about the optical field,electrical field and semiconductor materials is established.Taking the design trade-off between bandwidth and responsivity as an example,a general optimized method to alleviate the trade-off in the photodetector is proposed.(2)For the first time the carrier acceleration technology is proposed to alleviated the space-charge effect,and this technology is demonstrated on the silicon-based germanium photodetector.By introducing the additional electrical field,the nonuniform distribution of photocarriers in the photodetector is improved,thus the space-charge effect is alleviated,the large bandwidth is achieved under the high-power condition.More specifically,the device has a bandwidth of 23 GHz under the 5 d Bm input power.(3)Silicon-based germanium avalanche photodetector which is compatible with the CMOS fabrication process is proposed,designed,and fabricated.The micro-ring optical structure is introduced into the germanium avalanche photodetector.The avalanche photodetector has a gain of 5 under 20 GHz bandwidth.(4)A general structure of distributed-absorption regions is designed and discussed,and this structure is demonstrated on the silicon-based germanium photodetector.According to the discussion about the optimized number of distributed absorption regions,the design trade-off between bandwidth and saturated power is balanced from the theoretical model and experimental results,and the optimal number of distributed absorption regions is confirmed.Based this optimized optical structure,three photodetectors are realized with different electrodes,including the lumped one with a bandwidth of 49 GHz,traveling-wave one with a RF saturation power of 3.24 d Bm and the balanced one with a CMRR of 40 d B.Three photodetectors all achieves large-bandwidth and high-power performance,which show great application potentials.(5)With the help of high-performance germanium photodetectors,two monolithic integrated systems are proposed and demonstrated,including a mode-multiplexing photonics system for on-chip interconnects and parallel radio-frequency signal-processing unit for microwave photonics links.In the on-chip interconnects system,82 photonics devices,including 8 large-bandwidth photodetector arrays,are integrated and for the first time achieves 384 links for data exchanges.On the other hand,the mode-multiplexing technology is introduced into the integrated microwave photonics.The whole microwave filter has wide tuning range,due to the large-bandwidth photodetector.This system opens a new way to develop on-chip microwave photonics systems.
Keywords/Search Tags:Photodetector, Avalanche photodetector, Silicon photonics, Integrated photonics system, Microwave photonics, Optical interconnect
PDF Full Text Request
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