| Summary: | 博士 === 國立交通大學 === 電子工程學系 電子研究所 === 103 === The single photon avalanche photodiode (SPAD) exhibits ultra high photon sensitivity and timing resolution, hence it is currently being studied and used for the applications of biological fluorescence lifetime imaging microscopy and range-finder imaging. With this aim, in this thesis we use the Technology Computer Aided Design (TCAD) to simulate
the characteristics of SPAD, design structures of SPAD with different processes in TSMC, and characterize them by our measurement systems. We characterize SPADs with several important parameters, including the dark count rate (DCR), photon detection efficiency (PDE), timing jitter, and after-pulsing. This thesis introduces the measurement setups that can automatically acquire above parameters for evaluating the performance of various devices.
We design and compare two SPAD devices with breakdown voltage (VBre) of 10 V and 20 V by three different wells with different types of carriers and doping concentrations in TSMC 0.18 um complementary metal-oxide-semiconductor (CMOS) RF process. We design several structures to reduce the sources of DCR of SPAD device and modify the device layout for improving the fill factor of an array. Furthermore, we design different device structures with various VBre by the use of TSMC 0.18 um CMOS High Voltage process that has more choices of well with different doping concentrations. Among them, there are devices with different depths for the active region, resulting in different photon spectral response. The tunneling effect for devices with various VBre can be further analyzed in characterizing the DCR of these devices.
While SPAD is operated based on the ultra high electric field induced avalanche, an uniform electric field distribution is demanded for a consistent response in practical applications. In this thesis, we use the setup of 2D photon count mapping measurement system for examining the uniformity of electric field distribution in two SPADs with respectively high and low VBre. The SPAD with higher VBre has distinct depth-dependent non-uniformity of electric field distribution, but the SPAD with lower VBre has better uniformity of electric field distribution at all depths.
In the last part of this thesis, we explore both CMOS SPAD with low DCR and a commercial InGaAs SPAD as a radio thermometer and compare the measurement results to the theoretical calculations. According to the measurement results, the SPAD, as being a radio thermometer, has higher sensitivity than CCD. It is expected that the imaging array based on CMOS SPAD with enhanced performance and specially designed circuit will be a prospective thermal image camera which at the same time can capture the distance information of sensed object due to the high timing resolution of SPAD.
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