Low-Noise InGaAs/InP Single-Photon Avalanche Diodes for Fiber-Based and Free-Space Applications

We present the design and the experimental characterization of a new InGaAs/InP single-photon avalanche diode (SPAD), with two different diameters: i) a 10 μm device, suitable for optical fiber-based quantum applications; ii) a 25 μm one, more appropriate for free-space applications. Compared to a previous generation, we improved the design of the double zinc diffusion and optimized the layer structure. We achieved low dark count rate, around 1 kcps and 4 kcps at 225 K and 5 V excess bias for 10 μm and 25 μm devices, respectively, and down to few tens of counts per seconds at 175 K for the 10 μm detector. At 5 V excess bias and 225 K temperature, both devices also show a high photon detection efficiency (33% at 1064 nm, 31% at 1310 nm and 25% at 1550 nm for the 10 μm SPAD). Afterpulsing has been measured with a custom readout integrated circuit, achieving very low probability values. Timing jitter is comparable to previous-generation devices.