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

The ability to detect single photons has led to the advancement of numerous research fields1–11. Although various types of single-photon detector have been developed12, because of two main factors—that is, (1) the need for operating at cryogenic temperature13,14 and (2) the incompatibility with complementary metal–oxide–semiconductor (CMOS) fabrication processes15,16—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 performance19–21, 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 SPADs22–28 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. A germanium–silicon single-photon avalanche diode operated at room temperature shows a noise-equivalent power improvement over the previous Ge-based single-photon avalanche diodes by 2–3.5 orders of magnitude.