Non-avalanche single photon detection without carrier transit-time delay through quantum capacitive coupling

Abstract

Searching for innovative approaches to detect single photons remains at the center of science and technology for decades. This paper proposes a zero transit-time, non-avalanche quantum capacitive photodetector to register single photons. In this detector, the absorption of a single photon changes the wave function of a single electron trapped in a quantum dot (QD), leading to a charge density redistribution nearby. This redistribution translates into a voltage signal through capacitive coupling between the QD and the measurement probe. Using InAs QD/AlAs barrier as a model system, the simulation shows that the output signal reaches ~4 mV per absorbed photon, promising for high-sensitivity, ps single-photon detection.

Detecting Single Photons Using Capacitive Coupling of Single Quantum Dots

“…The potential of the sense probe under conditions shown in Figure c is taken as a baseline potential (black horizontal lines in Figure g,h), against which the sense probe potential varies over time. In Figure g, a potential change (Δ V sp1 ) occurs on the sense probe upon absorbing a single photon, which is caused by a charge redistribution in the QD due to the single-electron wave function difference between the GS and the ES, as discussed in detail in our previous work . Δ V sp1 vanishes upon the relaxation of the electron back to the GS.…”

“…In Figure 2g, a potential change (ΔV sp1 ) occurs on the sense probe upon absorbing a single photon, which is caused by a charge redistribution in the QD due to the single-electron wave function difference between the GS and the ES, as discussed in detail in our previous work. 36 ΔV sp1 vanishes upon the relaxation of the electron back to the GS. Since Γ er ≫ Γ ed , the electron lifetime τ 1 at the ES is mainly determined by the relaxation rate through: τ 1 ∼ 1/Γ er .…”

“…When the electron tunnels out of the QD (i.e., Γ er ≪ Γ ed ), the sense probe would be subject to an electrostatic potential change through a capacitive coupling between the QD and the probe. 36 The potential change on the sense probe is denoted by ΔV sp2 in Figure 2h, which is considered as an output signal for the detector. The amplitude of ΔV sp2 is on the order of e/C, where e is the elementary charge and C is the self-capacitance of the QD.…”

“…The voltage output signal originating from the charge redistribution has been discussed in detail in our previous work. 36 Here, using Mode II (type I band alignment) and Mode III (type II band alignment) as examples, we focus on assessing the values of potential changes caused by electron escaping from the QD with COMSOL simulations. Figure 6a is a three-dimensional (3D) schematic diagram of the detector used for the simulation.…”

“…Since Γ er ≫ Γ ed , the electron lifetime τ 1 at the ES is mainly determined by the relaxation rate through: τ 1 ∼ 1/Γ er . When the electron tunnels out of the QD (i.e., Γ er ≪ Γ ed ), the sense probe would be subject to an electrostatic potential change through a capacitive coupling between the QD and the probe . The potential change on the sense probe is denoted by Δ V sp2 in Figure h, which is considered as an output signal for the detector.…”