근적외선 단일 광자 검출기의 광자 측정 효율 상승에 대한 연구

Abstract

Recently, advanced driver assistance systems (ADASs) have been attracting much the attention because of their possibility of reducing traffic accidents as well as for convenient driving experience by self-driving technology. For ADADs, Light detection and ranging (LIDAR) system is the key role technology, since it has very good spatial resolution and a long sensing range. However, the existing LIDAR systems are generally high priced products with compound semiconductor materials, which is a big obstacle to the popularization. Therefore, silicon based detectors are a probable candidate for next generation technology, since they have a potential of lower cost production due to the low price of silicon materials and compatibility to complementary metal–oxide–semiconductor (CMOS) process and a great sensitivity improvement by nanotechnology. Among silicon based detectors, silicon based CMOS single photon avalanche diodes (SPADs) are expected to be a candidates of LIDAR system components. However, to be used in LIDAR for self-driving technology, the low photon detection efficiency (PDE) in near-infrared spectrum of silicon based CMOS SPADs should be improved. In order to propose a new structure for high PDE, the new structure have been investigated to improve the PDE using a TCAD simulation in near-infrared spectrum region. Part 1 and part 2 are the results of my works to investigate the simple method to improve the PDE in near-infrared spectrum of silicon based CMOS SPADs. In this thesis, ADASs and LIDARs are briefly introduced and discussed in first part. And Part 1 and part 2 have shown the research result of the simple method to improve the PDE in near-infrared spectrum of silicon based CMOS SPADs. In part 1, the silicon based CMOS SPAD for research have been designed and optimized. Firstly, the PN junction structure for the active layer was optimized with the test planar device. From the trade-off relation between the breakdown voltage and the photon detection probability, the doping concentration of the n layer was determined to 5×〖10〗^16 〖cm〗^(-3), where the photon detection probability becomes maximum at the allowable breakdown voltage within the criteria of self-driving technology. In addition, The additional guard-ring structure was added in SPAD structure to prevent the early breakdown at the edge of the anode layer. The finally optimized device has the breakdown voltage of 17.8 V. The operation test was performed using Mixedmode simulation and quenching circuit designed on the consideration of the operation range with the finally optimized device. The dead time of the designed device extracted from the operation test is 109 ns. In part 2, the graded doped PN structure have been applied to the previous designed devices in part 1. With this new approach, the finally designed devices have obtained the overall improvement in optical characteristics for the single photon detection at the wavelength near 900 nm. Firstly, we showed that the responsivity of the newly designed device is at least 15 % greater than the responsivity of the optimized device in part 1. Also, we showed that the PDE of the newly designed device is 3.60 %, which is about 2.6 times higher than the PDE of the previously designed device and comparable to nano-structured device. The dead time, extracted from the same operation test in part 1, of the newly designed device is 93 ns.