Electrical μ-Lens Synthesis Using Dual-Junction Single-Photon Avalanche Diode

This work presents a dual-junction, single-photon avalanche diode (SPAD) with electrical μ-lens designed and simulated in 90 nm standard complementary metal oxide semiconductor (CMOS) technology. The evaluated structure can collect the photons impinging beneath the pixel guard ring, as well as the pixel active area. The fill factor of the SPAD increases from 12.5% to 42% in comparison with similar works on the same technology, according to new charge collections. Although the designed SPAD suffers from high dark count rate (DCR of 300kHz at 0.17V excess bias at room temperature) due to high amount of tunneling which was predicted in previous similar works, it still can be used in different applications such as random number generators and charged particle positioning pixels.​