Lumerical Simulation of Surface-illuminated Silicon PIN Photodiodes for Datacenter Interconnects

Silicon photodiodes (SiPD) with positivc-intrinsic-negative (PIN) structures are expected to play an important role in reducing the cost of datacenter interconnects. This paper presents the simulation results for two types of PIN SiPD devices. The simulation is carried using the Device Suite from Ansys' Lumerical package. The study considers both the steady-state and transient regimes with either abrupt or diffused doping with a reverse bias of −3V. For the first device, referred to as structure a), with abrupt doping, the simulation package produced a full-width half-maximum (FWHM) of 13.0 ps and a 3-dB transit-limited bandwidth of 11.5 GHz at the anode. The respective cathode results were surprisingly 14.0 ps and 12.8 GHz. The simulation of structure a) with diffused doping did not produce a significant difference in the FWHM and transit-limited bandwidth results. However, the simulation of the second device, referred to as structure b), with abrupt doping yielded a FWHM of 11.5 ps at the anode and 16.0 ps at the cathode. The respective bandwidths were 7.9 GHz and 9.1 GHz. The preliminary results for the anode and cathode currents were consistent between the small-scale and large-scale structures.