Full-band Monte Carlo simulation of single photon avalanche diodes

Single photon avalanche diodes (SPADs) enable a variety of innovative applications in the fields of biology, medicine, and physics. The propagation of single photons with optical fibers requires the usage of telecommunication wavelengths in the near infrared (NIR) spectral range. NIR SPADs, which can be employed for this application, consist of an absorber layer (In_0.53Ga_0.47As) and a multiplication layer (InP or In_0.52Al_0.48As). The product of the quantum efficiency η_q, the probability that the photoexcited carrier survives into the multiplier P_c, and the breakdown probability P_b that the carrier activates a self-sustaining avalanche designate the photon detection efficiency [1] PDE = η_qP_cP_b. The breakdown probability contributes primarily to the electric field dependence of the PDE and increases with the electric field. Therefore, a higher electric field enhances the photon detection efficiency. However, band-to-band or trap-assisted tunneling in the multiplication layer initiate dark counts and degrade the performance of SPAD devices at higher electric fields. Hence, to obtain a higher photon detection efficiency for a given increase of the electric field and tunneling rate, a steep rise of the breakdown probability with applied bias is favorable. The SPAD´s timing jitter arises from various sources. The avalanche build-up time is the main contribution to the timing jitter [1].