Room temperature operation of germanium-silicon single-photon avalanche diode

The ability to detect single photons has led to the advancement of numerous research fields^1-11. Although various types of single-photon detector have been developed¹², because of two main factors-that is, (1) the need for operating at cryogenic temperature^13,14 and (2) the incompatibility with complementary metal-oxide-semiconductor (CMOS) fabrication processes^15,16-so far, to our knowledge, only Si-based single-photon avalanche diode (SPAD)^17,18 has gained mainstream success and has been used in consumer electronics. With the growing demand to shift the operation wavelength from near-infrared to short-wavelength infrared (SWIR) for better safety and performance^19-21, an alternative solution is required because Si has negligible optical absorption for wavelengths beyond 1 µm. Here we report a CMOS-compatible, high-performing germanium-silicon SPAD operated at room temperature, featuring a noise-equivalent power improvement over the previous Ge-based SPADs^22-28 by 2-3.5 orders of magnitude. Key parameters such as dark count rate, single-photon detection probability at 1,310 nm, timing jitter, after-pulsing characteristic time and after-pulsing probability are, respectively, measured as 19 kHz µm^-2, 12%, 188 ps, ~90 ns and <1%, with a low breakdown voltage of 10.26 V and a small excess bias of 0.75 V. Three-dimensional point-cloud images are captured with direct time-of-flight technique as proof of concept. This work paves the way towards using single-photon-sensitive SWIR sensors, imagers and photonic integrated circuits in everyday life.