Simulation of High-Efficiency Resonant-Cavity-Enhanced GeSn Single-Photon Avalanche Photodiodes for Sensing and Optical Quantum Applications

Two novel resonant-cavity-enhanced (RCE) GeSn single-photon avalanche photodiode (SPAD) detectors are designed and simulated for high-efficiency single-photon detection at 1550 and 2000 nm wavelength at room temperature for sensing and optical quantum applications. The RCE GeSn SPAD consists of a PIPIN GeSn/Si heterostructures embedded in an optical cavity formed by a distributed Bragg reflector (DBR) and GeSn surface. The results show that high photon absorption efficiency and avalanche triggering probabilities can be achieved by careful design of DBR reflectors, GeSn absorber, doping concentrations of Si charge sheet layer and multiplication layer, which lead to a high single-photon detection efficiency (SPDE) of ~80%, which is promising for emerging quantum applications demanding high SPDE, such as linear optical quantum computing. The noise equivalent power (NEP) and dark count rate (DCR) as a function of threading dislocations density (TDD) are examined as well. It is found that the device could operate near room temperature with a similar DCR level to that of Ge SPAD operating at low temperature. A NEP of
$\sim 3\times 10^{-15}$
W/Hz
$^{1/2}$
is observed from RCE GeSn SPAD for 1550 nm wavelength at room temperature. This work shows that the proposed RCE GeSn SPADs are promising candidates for high-efficiency single-photon detection in short-wave infrared (SWIR) regime for sensing and optical quantum applications.