Quantum dot infrared photodetector with gated-mode design for mid-IR single photon detection.

A novel design for a quantum dot infrared photodetector (QDIP) is proposed based on avalanche multiplication and is expected to be used as a single photon detector at mid-IR. A high field multiplication region is added to a conventional QDIP in separate absorption, charge, and multiplication structures to intensify incoming photocurrent generated in the absorption region. The absorption region of the photodetector consists of quantum dot layers that are responsible for absorption of mid-IR wavelengths. Because of higher operation voltages in gated-mode operation, resonant tunneling barriers are also included in the absorption region to prevent higher dark currents. The absorption region is designed for operation at λ=8 μm. During the gate pulse period, photo-generated electrons can trigger an avalanche and produce an output pulse. For this detector, the dark count rate (DCR) and single photon quantum efficiency (SPQE) are calculated at different temperatures. SPQE with peak of about 0.3 for T=50  K is obtained. For higher temperatures, about T=120 K, SPQE is very low due to the contribution of dark carriers generated in the quantum dot absorption region.