Proposal and demonstration of lock-in pixels for indirect time-of-flight measurements based on germanium-on-silicon technology.

We propose the use of germanium-on-silicon technology for indirect time-of-flight depth sensing as well as three-dimensional imaging applications, and demonstrate a novel pixel featuring a high quantum efficiency and a large frequency bandwidth. Compared to conventional silicon pixels, our germanium-on-silicon pixels simultaneously maintain a high quantum efficiency and a high demodulation contrast deep into GHz frequency regime, which enable consistently superior depth accuracy in both indoor and outdoor scenarios. Device simulation, system performance comparison, and electrical/optical characterization of the fabricated pixels are presented. Our work paves a new path to high-performance time-of-flight sensors and imagers, as well as potential adoptions of eye-safe lasers (wavelengths u003e 1.4 {mu}m) that fall outside of the operation window of conventional silicon pixels.