Size Effect and Crosstalk in Single Photon Avalanche Diodes

• Main Authors: Huang, Yi-Hsiang, 黃翊翔
• Other Authors: Lin, Sheng-Di
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/s5eawg

碩士 === 國立交通大學 === 電子研究所 === 105 === To improve the spatial resolution, the scale-down detector structure design becomes the recent research trend. Our group has developed a small size single-photon avalanche diodes (SPAD) with 8 μm diameter active region. Though it owns extremely low dark counts, its sensitivity is much lower. In this work, we design SPADs in standard 0.18 μm high-voltage CMOS technology provided by TSMC. By measuring the SPADs with various sizes, we analyze and investigate the size effect. With TCAD simulation, we observe that the high impact ionization area and its proportion to active region become smaller when SPADs scale down. We infer that decreasing impact ionization area proportion to active region may be the main reason to the lower sensitivity of small-size SPADs. With Size effect research, we can provide the information which is beneficial to SPAD array design. Besides, we provide two 2x2 SPAD array structure design: the one is the SPAD array with electrode-ring sharing, the other is cathode-well sharing SPAD array. Comparing to the conventional SPAD array, our work provides high filling- factor(FF) advantage, which FF is up to 34 %. Though our device design has higher DCR, it still owns the low dark counts and high detection efficiency. Since the SPAD array intensity increases by reducing the space between devices, optical crosstalk problem becomes the main issue. We attempt to research device crosstalk with the 2x8 SPAD array provided by ITRI. Through the measurement, we observe that the crosstalk decay follows the inverse ratio to the distance square. We infer direct optical path dominates optical crosstalk, which benefits us to design the minimum spacing between SPADs.