Quantum-Dot Single-Electron Transistors as Thermoelectric Quantum Detectors at Terahertz Frequencies

Abstract

Low dimensional nano-systems are promising candidates for manipulating, controlling and capturing photons with large sensitivities and low-noise. If quantum engineered to tailor the energy of the localized electrons across the desired frequency range, they can allow devising efficient quantum sensors across any frequency domain. Here, we exploit the rich few-electrons physics to develop millimeter-wave nanodetectors employing as sensing element an InAs/InAs0.3P0.7 quantum-dot nanowire, embedded in a single electron transistor. Once irradiated with light the deeply localized quantum element exhibits an extra electromotive force driven by the photothermoelectric effect, which is exploited to efficiently sense radiation at 0.6 THz with a noise equivalent power < 8 pWHz -1/2 and almost zero dark current. The achieved results open intriguing perspectives for quantum key distributions, quantum communications and quantum cryptography at terahertz frequencies.

Introductory Chapter: The Fame of Quantum Dots in Space-age Improvements for Multifunctional Application

“…• Trap engineering in PbSe quantum dots for photodetectors [19] • Wave function engineering-Type-I/II Excitons [20] • Large-scale production of quantum dots for energy storage applications [21] • Efficient calibration of crosstalk in a quadruple quantum dot array [22] Photonic devices • Quantum dot-Si photonic integrated circuits [23] • High-quality quantum dot laser/waveguide [24] • QDs and nano-photonic waveguides [25] Optoelectronics • Semiconductor quantum dot for photovoltaic applications [26] • Quantum dot optoelectronics [27] • Quantum dot semiconductor optical amplifiers (QD-SOA) [28] • Flexible quantum dot light-emitting diodes [29] Electronics • Single-electron transistors with quantum dots [30] • High-Performance quantum dot thin-Film transistors [31] • Integrated circuits (VLSI, hybrid integrated) [32] • Single quantum emitter detection with amateur CCD [33] Electricity (without semiconductors)…”

Semiconductor Nanowire Field-Effect Transistors as Sensitive Detectors in the Far-Infrared

“…At V G = −2 V (Figure 4b), the THz-on and THz-off traces almost overlapped, and the effect of THz radiation was visible only as a positive change of the NW conductivity ∆σ/σ = 4%, i.e., an increase in σ when the system was heated by the THz beam. At V G = 11.3 V, instead, there was a rigid shift of the I SD vs.V SD characteristic towards positive currents, as a consequence of an additional electromotive force along the channel, which pushed electrons from S to D. We ascribed this contribution to the PTE-driven photocurrent: I PTE = −σS b ∇T, where S b is the NW Seebeck coefficient and ∇T is the THz-induced (positive) thermal gradient between the D (cold) and S (hot) electrodes, resulting in I SD = σ(V SD -S B ∇T) [38] (here a positive V SD corresponds to a negative electrostatic voltage gradient from D to S). Importantly, for V G > 3 V, the BE was still observable in a negative ∆σ/σ = −5%, in agreement with the expected trend of ∆u B (V G ).…”

“…The detection dynamics in homogeneous InAs NWs have been investigated by THz scattering near-field optical microscopy (SNOM), in a recent work [37], which evidenced the interplay of two thermal effects ignited under photoexcitation: the bolometric effect (BE), activated at low carrier densities (n~10 16 cm −3 ), and the photo-thermoelectric effect (PTE), activated at high carrier densities (n 10 17 cm −3 ). The PTE effect has also been studied in quantum dots, defined in axially heterostructured InAs/InAs 0.3 P 0.7 NWs [38] under excitation with photon energies lower than the inter-level spacing. Photodetection in an NW-QD is governed by the Seebeck effect, whose amplitude can be manipulated externally by applying an electrostatic gating to the QD.…”

Absorption Enhancement in a Quantum Dot Thz Detector with a Metal-Semiconductor-Metal Structure

“…In recent years, quantum dot detectors have shown favorable characteristics, such as low dark current, high responsivity, and high detectivity due to the unique threedimensional constrained quantum dot nano-structure in the detection application of the environmental pollution, protection, and they have gained more attention [1,2]. Although highly efficient and miniatured quantum dot detectors can be achieved, reports pointed out that quantum dot detectors could suffer inhomogeneous size distribution and nonoptimized energy bands [3,4], which can lead to a reduction in absorption rate and sensitivity of the detectors.…”