Single-photon avalanche diodes for short-wave infrared detection

Abstract

Single-photon detection is an exciting and rapidly advancing field with numerous emerging applications areas. There is a demand for highly efficient low noise single-photon detectors. 1310 and 1550 nm are particularly desirable detection wavelengths for use in time-of-flight imaging, light detection and ranging in automobiles, and low loss optical fibre transmission in quantum key distribution networks. Silicon based single-photon detectors dominate in the visible and near-infrared spectral ranges, but this report investigates the design and characterisation of planar Germanium-on-Silicon Single-Photon Avalanche Diodes (SPADs) as an efficient short-wave infrared detector. A single-photon detection efficiency of up to 30 % at a temperature of 125 K was achieved at a wavelength of 1310 nm, with dark count rates in the order of a few thousand counts per second, a low noise equivalent power of 4 x10 -17 WHz-1/2 and timing jitter as low as 126 ps at 150 K. These results represent the highest sensitivity and lowest jitter Ge-on-Si SPAD detectors demonstrated. These planar geometry Ge-on-Si SPADs show potential for operation at Peltier cooled temperatures and easy integration into readily available Si SPAD circuitry as well as high efficiency single-photon detection. Further investigation was performed into altering the thickness of the germanium absorption layer within the Ge-on-Si devices and the results showed potential to improve the single-photon detection efficiency with a refined fabrication process by growing thicker Ge layers to increase the absorption of SWIR photons. A selection of avalanche photodiodes fabricated in the alternative material system of InGaAsSb/GaSb and AlGaAsSb/GaSb were also investigated for operation in the short-wave infrared region.