High efficiency planar geometry germanium-on-silicon single-photon avalanche diode detectors

Abstract

This paper presents the performance of 26 μm and 50 µm diameter planar Ge-on-Si single-photon avalanche diode (SPAD) detectors. The addition of germanium in these detectors extends the spectral range into the shortwave infrared (SWIR) region, beyond the capability of already well-established Si SPAD devices. There are several advantages for extending the spectral range into the SWIR region including: reduced eye-safety laser threshold, greater attainable ranges, and increased depth resolution in range finding applications, in addition to the enhanced capability to image through obscurants such as fog and smoke. The time correlated single-photon counting (TCSPC) technique has been utilized to observe record low dark count rates, below 100 kHz at a temperature of 125 K for up to a 6.6 % excess bias, for the 26 µm diameter devices. Under identical experimental conditions, in terms of excess bias and temperature, the 50 µm diameter device consistently demonstrates dark count rates a factor of 4 times greater than 26 µm diameter devices, indicating that the dark count rate is proportional to the device volume. Single-photon detection efficiencies of up to ~ 29 % were measured at a wavelength of 1310 nm at 125 K. Noise equivalent powers (NEP) down to 9.8 × 10-17 WHz-1/2 and jitters < 160 ps are obtainable, both significantly lower than previous 100 μm diameter planar geometry devices, demonstrating the potential of these devices for highly sensitive and high-speed imaging in the SWIR.

Simulation and design optimization of germanium-on-silicon single photon avalanche diodes

“…We have previously demonstrated novel pseudo-planar germanium-on-silicon SPADs with absorption into the SWIR, which offer the prospect of lower costs, and easier CMOS integration compared to III-V SPADs. [7][8][9] There is significant scope to optimize these devices in order to make the technology competitive with InGaAs/InP SPAD devices; this is facilitated using process and device simulation to guide design decisions. Our model uses technology computer aided design (TCAD) for simulating the fabrication and electrical properties of a device, but requires additional custom code to predict device metrics including dark count rate (DCR) and single photon detection efficiency (SPDE).…”

Silicon-Based Avalanche Photodiodes: Advancements and Applications in Medical Imaging

“…Compared to III-V devices, silicon/germanium APDs and SPADs exhibit reduced afterpulsing effects and offer a cost-effective device platform [39][40][41]. Researchers are currently focused on improving these devices by addressing issues related to noise, cost, and compatibility with traditional circuits, in order to fully leverage the advantages of silicon-based systems [42][43][44][45].…”

Pseudo-planar Ge-on-Si single photon avalanche diode detector with record low noise-equivalent power

“…Here we present results from technology based on the Ge-on-Si material platform, which can operate in the SWIR but using Si foundry compatible growth and processing [10][11][12][13], giving it the potential for low-cost at mass-volume production. We demonstrate that a pseudo-planar device design can substantially improve the sensitivity of Ge-on-Si SPADs compared to simple mesa etched designs [14,15], yielding a step-change in performance, with 26 µm diameter devices showing record low noise-equivalent powers [16].…”