A 73% Peak PDP Single-Photon Avalanche Diode Implemented in 110 nm CIS Technology With Doping Compensation

Abstract

In this article, we present 10 μm diameter SPADs fabricated in 110 nm CIS technology based on an N+/HVPW junction, with enhanced sensitivity at short wavelengths. To reduce tunneling noise due to the highly-doped layers in the process, a doping compensation technique is used, which allows to adjust the doping profile of the HVPW. Thanks to this technique, DCR is reduced by a factor of 24 at 2 V excess bias voltage when compared to non-compensated devices. Furthermore, the maximum achievable PDP is enhanced by 49% thanks to the much lower DCR leading to a PDP of 73%, the highest ever reported at 440 nm, while the DCR is 12.5 cps/μm2, all at the 5 V excess bias. Since the junction is formed very close to the surface, the SPAD has excellent sensitivity in the UV spectrum, with a PDP of 43% at a wavelength of 350 nm. The proposed SPAD also achieves a PDP of 7% with a timing jitter of 68 ps at 850 nm at 5 V excess bias, which makes the device very useful for RGB-Z (RGB-D) sensors.