Lateral separate absorption charge multiplication Ge-on-Si avalanche photodiode with low dark current in linear mode

To suppress the dark current and improve the detection sensitivity of the Germanium-on-silicon (Ge-on-Si) avalanche photodiode (APD), we report an integrated waveguide-based Ge-on-Si APD with a lateral separate absorption charge multiplication (SACM) structure, which works at low bias voltage. The breakdown voltage (Vbr) of the lateral SACM APD in linear mode is about 5.81 V, and the device demonstrates very low dark current of 0.157 nA and 40.7 nA at unity gain voltage (VGain=1=3.5 V) and 0.95Vbr (∼5.5 V), at room temperature. We also study the single photon detection performance of the device in Geiger mode. The practical dark count rate (DCR) at 300 K is with the same order of magnitude as the vertical SACM Ge-on-Si APD operating at 200 K. With the wavelength and average photon number of weak coherent pulse are 1550 nm and 0.1, respectively, the theoretical single photon detection efficiency (SPDE) of the device can achieve 0.4% at 300 K, which will reduce the dependence of the weak light detection system on the low-temperature working environment.