Ge-on-Si Avalanche Photodiodes for LIDAR Applications

In order to make autonomous driving in cars possible, a precise knowledge of the immediate surroundings is required. One technology for near-field detection is the LIDAR (light detection and ranging) technology. Currently available LIDAR systems operate at a wavelength of 905 nm. However, for wavelengths from 1,300 nm, a significant increase in range resolution is achieved. Here, the receiver side is typically realized as APDs (avalanche photodiodes). In this work the fabrication and characterization of APDs with an absorption region made from Germanium (Ge) are presented. The layer sequence for the APDs are grown directly on Silicon (Si) substrate using a molecular beam epitaxy system. At room temperature the Ge-on-Si-APDs achieve responsivities of up to 6 A/W at a wavelength of 1,310 nm, which corresponds to a gain of 26 compared to conventional Ge photodiodes.