Abstract
We present our work on high performance germanium (Ge) quantum dot (QD) photodetectors (PDs), fabricated on Si and Ge substrates, that operate via tunneling transport through a QD-containing active layer and feature high internal photoconductive gain. In the λ = 400–1100 nm range, the PDs fabricated on Si substrates exhibit room-temperature spectral responsivity (Rsp) up to 4 A/W and internal quantum efficiency (IQE) up to 700%. At λ = 640 nm and 12μW of incident power, signal-to-noise ratio (SNR) of 7×106 and specific detectivity (D*) of 1.2×1011 cmHz1/2W−1 are obtained. The PDs demonstrate 3 dB bandwidths (f3dB) up to 10 MHz, corresponding to response times of ∼ 40 ns. When operated at 100 K temperature the performance improves, especially at low incident power, where at 10 nW D* increases to 2×1013 cmHz1/2W−1, due to IQE in excess of 22000%. In order to extend the photoresponse into the near-infrared (near-IR), PDs were fabricated on Ge substrates, yielding room-temperature Rsp = 1.5 A/W, IQE = 134% and f3dB = 10 kHz at the λ = 1550 nm telecommunication wavelength. Significant improvement to f3dB is expected in PDs employing thinner QD-containing layers. Lowering temperature to 50 K and incident power to 10 nW yield D* = 1013 cmHz1/2W−1, resulting from IQE exceeding 60000%. Based on the above figures of merit, as well as their Si technology compatibility, our Ge QD PDs appear promising for high-performance photodetectors working in the visible and near-IR.
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