서강대학교

초록/요약

This thesis focuses on an improved circuits for silicon single-photon avalanche photodiodes (SPADs). SPADs are designed and fabricated with a standard CMOS technology. By conducting CAD simulation for optimum device structures in a standard CMOS technology, SPADs having high gain and large bandwidth are implemented. A CMOS photo detection bias quenching circuit is developed to be used with single-photon avalanche photodiodes (SPADs) operating in Geiger mode for the detection of weak optical signals. The proposed bias quenching circuits for the performance improvement reduce the circuit size and improve the performance of the quenching operation. They are fabricated in a 0.18-μm standard CMOS technology to verify the effectiveness of this technique with the chip area of only 300 μm2, which is about 60 % of the previous reported circuit. Two types of proposed circuits with resistive and capacitive load demonstrated improved performance of reduced quenching time. With a commercial APD by HAMAMATSU, the dead time can be adjusted as small as 50 ns. Also, to maintain a constant passive quenching time and voltage, the calibration circuit is designed to flow a constant current through the quenching capacitor C. The calibration circuit is composed of a dummy capacitor with the identical size of as the quenching capacitor, a current mirror to pumping a constant current, and a detection circuit to detect the passive quenching voltage. The dead time can be adjusted manually about from 50 ns to 10 μs. For the power consumption, the proposed circuit with calibration scheme dissipates 600 µA from 3.3-V supply, while the conventional circuit dissipates 950 µA from 3.3-V supply. Lastly, to enhance the photon detection efficiency, the micro pixel array structure is proposed. The micro pixel array is composed of 4 × 4 single micro pixels. The dead time of the micro pixel array is longer than that of the single micro pixel (150 ns) due to the additional capacitance. However, to use the pixel array structure, the single photon response (gain) is enhanced.