High sensitivity Ge-on-Si single-photon avalanche diode detectors

Area of Science:

• Optoelectronics
• Semiconductor device physics
• Photonics

Background:

• Germanium-on-silicon (Ge-on-Si) technology is crucial for developing advanced photodetectors.
• Single-photon avalanche diodes (SPADs) are essential for low-light level detection.
• Existing Ge-on-Si SPADs face challenges with dark count rates and noise equivalent power (NEP).

Purpose of the Study:

• To present the performance of planar geometry Ge-on-Si SPAD detectors.
• To evaluate dark count rates, single-photon detection efficiency, and noise characteristics.
• To assess the potential of these detectors for sensitive optical measurements.

Main Methods:

• Fabrication and characterization of 26µm diameter planar Ge-on-Si SPADs.
• Measurement of dark count rates (DCR) at various excess biases and temperatures.
• Determination of single-photon detection efficiency (SPDE) and timing jitter.

Main Results:

• Record low dark count rates below 100 K counts per second achieved at 6.6% excess bias and 125 K.
• Single-photon detection efficiencies up to 29.4% demonstrated, with temperature insensitivity.
• Significantly reduced noise equivalent power (NEP) of 7.7×10⁻¹⁷ W/Hz, a two-order-of-magnitude improvement over previous mesa devices.

Conclusions:

• The developed planar Ge-on-Si SPADs exhibit excellent performance metrics.
• Low DCR, high SPDE, and reduced NEP make these detectors highly suitable for demanding applications.
• The demonstrated characteristics represent a significant advancement in Ge-on-Si SPAD technology.