Hybrid Dirac semimetal-based photodetector with efficient low-energy photon harvesting

Abstract

Despite the considerable effort, fast and highly sensitive photodetection is not widely available at the low-photon-energy range (~meV) of the electromagnetic spectrum, owing to the challenging light funneling into small active areas with efficient conversion into an electrical signal. Here, we provide an alternative strategy by efficiently integrating and manipulating at the nanoscale the optoelectronic properties of topological Dirac semimetal PtSe₂ and its van der Waals heterostructures. Explicitly, we realize strong plasmonic antenna coupling to semimetal states near the skin-depth regime (λ/10⁴), featuring colossal photoresponse by in-plane symmetry breaking. The observed spontaneous and polarization-sensitive photocurrent are correlated to strong coupling with the nonequilibrium states in PtSe₂ Dirac semimetal, yielding efficient light absorption in the photon range below 1.24 meV with responsivity exceeding ∼0.2 A/W and noise-equivalent power (NEP) less than ~38 pW/Hz^0.5, as well as superb ambient stability. Present results pave the way to efficient engineering of a topological semimetal for high-speed and low-energy photon harvesting in areas such as biomedical imaging, remote sensing or security applications.

Fig. 1. Scaling law of plasmonic near-field characteristic toward the skin-depth regime.

a Schematics of the bow-tie antenna-assisted device. b, c The cross-section view of the simulated electric field intensity normalized to incident one marks the power-gain around the nanochannel at 0.3 THz electromagnetic waves. Localized oscillating electric field enhancement in the sub-100 nm channel by light-induced current charges. d The profile of electric field distribution along the x-axis. e, f The scaling of electric field enhancement derived from FDTD method versus channel length and incident frequency. g The spatial distribution of the electric field near the 100 nm gapped channel substantiates the strong focusing induced by the oscillating charge

Fig. 2. The nanogap slit fabrication technology and s-SNOM.

a The nanogap slit device fabrication process, including PtSe₂ fabrication, ultraviolet lithography, lift-off processes, and tilt deposition. b Schematic of the bow-tie antenna-assisted device. c–e Optical microscopy and false-color SEM images of the PtSe₂ nanogap slit device with a typical channel length (100 nm and 30 nm). f The near-field images are taken around the slit area using broadband illumination. g Stereograph of the near-field signal

Fig. 3. Characteristics of the PtSe2 low-energy photon detector.

a Schematic diagram of the experimental geometry, with photon-beam spot profile (diameter: 800 μm), derived from two-dimensional scanning of the photodetector. b The band diagram at the different metal junction regions with/without bias. c Bias dependence of responsivity at 0.12 THz and 0.3 THz for different channel lengths. d The measured photocurrent vs. output power P_in, with the power, varied from 0.3 μW to 300 μW. The channel length of the typical microgap slit and nanoslit device is 4 μm and 100 nm, respectively. e, f The conversion efficiency of the nanogap slit photodetector versus the incident power at room temperature. g Pt-4f and Se-3d core levels, measured at a photon energy of 400 eV. h Time-resolved photo signal of PtSe₂-based nanogap slit photodetector at V_bias = 0 V

Fig. 4. Characteristics of the PtSe2/graphene low-energy photon detector.

a Schematic diagram of the device architecture. Inset: the optical micrograph of the device. b Schematic band diagram of PtSe₂-graphene heterostructure. c The measured photocurrent vs. incident power P_in with the power varied from 0.3 μW to 300 μW. d Bias dependence of photocurrent at 0.3 THz, yielding responsivity of 0.08 A/W at unbiased voltage. e Comparisons of NEP at 0.3 THz among pristine metal-PtSe₂-metal, asymmetric nanogap slit device, and PtSe₂-graphene vdW heterostructure. f Summary of the measurement of our devices and comparison with past works. PTE = photo-thermoelectric effect, Dyakonov-Shur PWT = Dyakonov-Shur plasma wave theory, SBD = Schottky barrier diode, FET = Field-Effect Transistors. Black phosphorus (BP)/hBN heterostructure (ref. ), BP FET (ref. ), Bi₂Te_(3−x)Se_x FET (ref. ), BP nano-transistors (ref. ), Nanowire (NW) Field-Effect Transistors (ref. ), Se-doping InAs NWs FETs (ref. ), Hg_1–xCd_xTe (ref. ), CVD Graphene (ref. ), Antenna Enhanced Graphene (ref. ), InGaAs Schottky barrier diode (SBD) array (ref. ), Graphene ballistic rectifier (ref. ), Commercial Golay (ref. ), Commercial VDI (ref. ), SBD FETs (ref. ). The pick represents the performance of nanoslit and heterostructure devices, respectively. g The optical picture of a fresh leaf and a metallic ring used in the imaging and 0.3 THz transmissions nondestructive image of the fresh leaf demonstrates the leaf vein, which partly contains more moisture