The design, modeling, fabrication, and characterization of single-photon avalanche diode detectors with an epitaxial Ge absorption region grown directly on Si are presented. At 100 K, a single-photon detection efficiency of 4% at 1310 nm wavelength was measured with a dark count rate of ∼6 megacounts/s, resulting in the lowest reported noiseequivalent power for a Ge-on-Si single-photon avalanche diode detector (1 × 10 −14 WHz −1/2 ). The first report of 1550 nm wavelength detection efficiency measurements with such a device is presented. A jitter of 300 ps was measured, and preliminary tests on after-pulsing showed only a small increase (a factor of 2) in the normalized dark count rate when the gating frequency was increased from 1 kHz to 1 MHz. These initial results suggest that optimized devices integrated on Si substrates could potentially provide performance comparable to or better than that of many commercially available discrete technologies.Index Terms-Detector, germanium on silicon, single-photon avalanche diode, single-photon counting.
Gunn oscillations have been observed and modelled, using a Monte Carlo method, in planar semiconductor GaAs/AlGaAs heterostructure diodes. Our simulation results support an interpretation of experimental results whereby the Gunn domains travel parallel to the semiconductor layers, as opposed to perpendicular to the layers in traditional vertical devices. Fabricated devices with contact separations of 4 µm down to 1.3 µm have been found to oscillate over a range of frequencies from 24.5 GHz to 108 GHz. These structures offer the prospect of generating frequencies further into the terahertz range and an increased ease of integration and flexibility over equivalent traditional vertical structures.
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