Ge-on-Si SPAD LiDAR

Optics Express paper "3D LIDAR imaging using Ge-on-Si single–photon avalanche diode detectors" by Kateryna Kuzmenko, Peter Vines, Abderrahim Halimi, Robert J. Collins, Aurora Maccarone, Aongus McCarthy, Zoë M. Greener, Jarosław Kirdoda, Derek C. S. Dumas, Lourdes Ferre Llin, Muhammad M. Mirza, Ross W. Millar, Douglas J. Paul, and Gerald S. Buller from Heriot-Watt and Edinburgh Universities, UK, presents a concept design of LiDAR with a SPAD detector cooled down to 100K:

"We present a scanning light detection and ranging (LIDAR) system incorporating an individual Ge-on-Si single-photon avalanche diode (SPAD) detector for depth and intensity imaging in the short-wavelength infrared region. The time-correlated single-photon counting technique was used to determine the return photon time-of-flight for target depth information. In laboratory demonstrations, depth and intensity reconstructions were made of targets at short range, using advanced image processing algorithms tailored for the analysis of single–photon time-of-flight data. These laboratory measurements were used to predict the performance of the single-photon LIDAR system at longer ranges, providing estimations that sub-milliwatt average power levels would be required for kilometer range depth measurements.

... recently, the use of planar geometry devices [39] yielded a significant step change improvement in performance. Vines et al. [39] reported a normal incidence planar geometry Ge-on-Si SPADs with 38% SPDE at 125 K at a wavelength of 1310 nm and a noise–equivalent power (NEP) of 2 × 10−16 WHz-1/2. In addition, these devices clearly demonstrated lower levels of afterpulsing compared with InGaAs/InP SPAD detectors operated under nominally identical conditions. The high SPDEs of Ge-on-Si SPADs and their reduced afterpulsing compared to InGaAs/InP SPADs provides the potential for significantly higher count rate operation and, consequently, reduced data acquisition times. Planar Ge-on-Si SPADs exhibit compatibility with Si CMOS processing, potentially leading to the development of inexpensive, highly efficient Ge-on-Si SPAD detector arrays. Here we report a successful demonstration of LIDAR 3D imaging using an individual planar Ge-on-Si SPAD operating at a wavelength of 1450 nm."