High-Performance Germanium-an-Silicon Lock-in Pixels for Indirect Time-of-Flight Applications

We investigate and demonstrate the first Ge-on-Si lock-in pixels for indirect time-of-flight measurements. Compared to conventional Si lock-in pixels, such novel Ge-on-Si lock-in pixels simultaneously maintain a high quantum efficiency and a high demodulation contrast at a higher operation frequency, which enable consistently superior depth accuracies for both indoor and outdoor scenarios. System performances are evaluated, and pixel quantum efficiencies are measured to be >85% and >46% at 940nm and 1550nm wavelengths, respectively, along with demodulation contrasts measured to be >0.81 at 300MHz. Our work may open up new routes to high-performance indirect time-of-flight sensors and imagers, as well as potential adoptions of eye-safe lasers (e.g. wavelengths > $1.4\mu\mathrm{m})$ ) for consumer electronics and photonics.