Detecting Single Photons Using Capacitive Coupling of Single Quantum Dots

Capturing single photons through light–matter interactions is a fascinating and important topic for both fundamental research and practical applications. The light–matter interaction enables the transfer of the energy of a single photon (∼1 eV) to a bound electron, making it free to move either in the crystal lattice or in the vacuum. In conventional single photon detectors (e.g., avalanche photodiodes), this free electron triggers a carrier multiplication process which amplifies the ultraweak signal to a detectable level. Despite their popularity, the timing jitter of these conventional detectors is limited to tens of picoseconds, mainly attributed to a finite velocity of carriers drifting through the detectors. Here we propose a new type of single photon detector where a quantum dot, embedded in a single-electron transistor like device structure, traps a photogenerated charge and gives rise to a sizable voltage signal (∼7 mV per electron or hole by simulation) on a nearby sense probe through capacitive coupling (with a capacitance ∼ aF). Possible working modes of the proposed detector are theoretically examined. Owing to a small lateral dimension of the quantum dot, detailed analyses reveal that the intrinsic timing jitter of the proposed detector is in the femtosecond to subpicosecond range, and the intrinsic dark count rate is negligible up to moderately high temperatures. These figures of merit are orders of magnitude superior to those of the state-of-the-art single photon detectors work in the same spectral range, making the proposed detector promising for timing-sensitive and quantum information applications.