Interface State Calculation of the Wafer-Bonded Ge/Si Single-Photon Avalanche Photodiode in Geiger Mode

More and more attention has been paid to the heterogeneous semiconductor device based on the wafer-bonding method due to its high-quality wafer-bonded active layer. In this paper, we first theoretically study the dependence of the single-photon properties, including the single-photon detection efficiency (SPDE), dark count rate (DCR), and afterpulsing probability (AP), of the wafer-bonded Ge/Si single-photon avalanche photodiode (SPAD) on the interface state at the Ge/Si (hydrophilic reaction) and Si-Si (hydrophobic reaction or surface-activated method) wafer-bonded interface based on the Poisson statistics. It is found that the interface state density and the energy level position of the interface state significantly affect the linear-mode electric field distribution (avalanche probability), 3-dB bandwidth (dark carriers), gain (quantum efficiency), and effective transit time (trapped carriers), which in turn affect the DCR and the SPDE. Furthermore, the dependence of the AP on the avalanche charge and the interface recombination rate is clarified as well. It is expected that this paper may give guidance for the fabrication of high-performance SPAD.