Abstract—We demonstrate a sinusoidally-gated InGaAs/InP photodiode pair operated at wavelength of 1310 nm with high photon detection efficiency (PDE) and low dark count rate (DCR). The photodiode pair is biased in a balanced scenario so that the common component of the output signal is cancelled. The concept of balanced photodiodes helps improve detection efficiency while canceling the common mode signal, which, in this case, is the capacitive response of the photodiodes. In conventional sinusoidal gating, an extra component, – an RF filter (or several) at the gating frequency, is utilized to filter out the gating signal and leave the avalanche signal for detection. For this configuration, sinusoidally-gated counting systems are restricted to a single frequency. With the balanced single photon diodes (SPAD), sinusoidal gating within a continuous frequency range is feasible. A printed circuit with symmetric layout of two bias tees was fabricated on a duroid board to enable the application of AC and DC signals for the dual SPADs. At a laser repletion rate of 1 MHz and temperature of 240 K the DCR and PDE were 58 kHz and 43%, respectively. Afterpulsing probability was lower compared with a sinusoidually-gated single SPAD. Jitter of 240 ps was achieved with 1 photon per pulse for an excess bias of 1.6%.
We report sinusoidal gating of InGaAs/InP single photon avalanche diodes (SPAD) operated
at wavelength of 1310 nm with high photon detection efficiency (PDE) and low dark count rate (DCR).
At a gating frequency of 80 MHz and temperature of 240 K the DCR and PDE were 15.5 kHz and 55%,
respectively. The slope of DCR versus PDE increases with higher laser repetition rate. There are two
mechanisms that contribute to this trend. The first is due to the lower afterpulse probability associated
with a lower laser repetition rate. The other is due to the RC effect, which is illustrated by an equivalent
circuit that includes a model of the SPAD. We also show that relative to gated passive quenching with
active reset (PQAR) for fixed PDE, sinusoidal gating yields lower afterpulsing rates for the same hold-off
time. This is explained in terms of the integrated pulse shape and the resultant charge flow. The afterpulse
probability, P<sub>a</sub>, is related to the hold off time, T, through the power law, <i>P<sub>a</sub>∝T<sup>-α</sup></i> where α is a measure of the detrapping time in the multiplication region.
We demonstrate Ge metal-semiconductor-metal (MSM) photodetectors monolithically integrated with silicon-oxynitride
(SiO<sub>x</sub>N<sub>y</sub>) waveguides. Ge photodetector layer was epitaxially grown by an UHVCVD system and the
waveguide was formed on top of the Ge photodetector by PECVD. The entire process is found to be completely
compatible with the standard CMOS process. Light is evanescently coupled from silicon-oxynitride (SiO<sub>x</sub>N<sub>y</sub>)
waveguide to the underlying Ge photodetector, achieving at 2 V a responsivity of 0.33 A/W at 1.55 μm wavelength
and a dark current of 1 μA for a 10 μm long photodetector.
We report reduced afterpulsing for a high-performance InGaAs/InP single photon avalanche photodiode (SPAD) using a
gated-mode passive quenching with active reset (gated-PQAR) circuit. Photon detection efficiency (PDE) and dark count
probability (DCP) were measured at a gate repetition rate of 1 MHz. With a double-pulse measurement technique, the
afterpulsing probability was measured for various hold-off times. At 230K, 0.3% afterpulsing probability for a 10 ns
hold-off time was achieved with 13% PDE, 2×10<sup>-6</sup> DCP and 0.4 ns effective gate width. For the same hold off time,
30% PDE and 1×10<sup>-5</sup> DCP was achieved with 6% afterpulsing probability for an effective gate width of 0.7 ns.
Avalanche Photodiodes (APDs) are widely used in fiber-optic communications as well as imaging and sensing
applications where high sensitivities are needed. Traditional InP-based APD receivers typically offer a 10 dB
improvement in sensitivity up to 10 Gb/s when compared to standard p-i-n based detector counterparts. As the data rates
increase, however, a limited gain-bandwidth product (~100GHz) results in degraded receiver sensitivity. An increasing
amount of research is now focusing on alternative multiplication materials for APDs to overcome this limitation, and one
of the most promising is silicon. The difficulty in realizing a silicon-based APD device at near infrared wavelengths is
that a compatible absorbing material is difficult to find. Research on germanium-on-silicon p-i-n detectors has shown
acceptable responsivity at wavelengths as long as 1550 nm, and this work extends the approach to the more complicated
APD structure. We are reporting here a germanium-on-silicon Separate Absorption Charge and Multiplication (SACM)
APD which operates at 1310 nm, with a responsivity of 0.55A/W at unity gain with long dark current densities. The
measured gain bandwidth product of this device is much higher than that of a typical III-V APD. Other device
performances, like reliability, sensitivity and thermal stability, will also be discussed in this talk. This basic
demonstration of a new silicon photonic device is an important step towards practical APD devices operating at 40 Gb/s,
as well as for new applications which require low cost, high volume receivers with high sensitivity such as imaging and