Tunneling light emitting device based on barrier-mode field impedance matching and modulation method thereof

Abstract

The application discloses a tunneling light-emitting device based on barrier-mode field impedance matching and a modulation method thereof, comprising a substrate, an insulating tunneling layer arranged on the substrate, and a metal nano antenna array arranged on the insulating tunneling layer, wherein the metal nano antenna array is a periodically arranged metal strip array, and the geometric parameters of the metal nano antenna array and the electrical parameters of the insulating tunneling layer are cooperatively configured, so that, under the bias voltage of the tunneling light-emitting device, the differential tunneling resistance of the insulating tunneling layer and the equivalent radiation impedance of the metal nano antenna array at the excitation wavelength realize conjugate matching or mode value matching, so as to promote the efficient transfer of the tunneling electron energy to the optical mode; the advantage is that the critical coupling of the electron tunneling rate and the optical mode radiation rate can be realized, so that the electroluminescent efficiency is significantly improved, and the energy transmission efficiency is relatively high.

Description

Technical Field

[0001] This invention relates to tunneling light-emitting devices, and more particularly to a tunneling light-emitting device based on barrier-mode field impedance matching and its modulation method. Background Technology

[0002] Achieving silicon-based light sources compatible with CMOS processes is a key technological requirement in the current field of microelectronics and optoelectronics integration. Light-emitting devices based on inelastic electron tunneling (IET), also known as tunneling light-emitting devices, have attracted attention due to their simple structure and the fact that they do not require the integration of heterogeneous materials.

[0003] Traditional tunneling light-emitting devices are planar MIS tunnel junctions, typically employing a metal-insulator-semiconductor (MIS) structure (e.g., Al / Al₂O₃ / Si planar structure). Their electron tunneling momentum is primarily distributed along the electric field direction perpendicular to the interface. However, photonic or surface plasmon polariton (SPP) modes usually possess a large in-plane momentum component. This momentum mismatch causes the vast majority of tunneling electrons to undergo nonradiative transitions via excited phonons (thermal dissipation). Therefore, traditional tunneling light-emitting devices have extremely low external quantum efficiency (EQE), with tunneling probabilities typically less than 10⁻⁶. -6 .

[0004] To address the aforementioned issues, some researchers have proposed integrating grating structures onto the surface of planar MIS tunnel junctions to form tunneling light-emitting devices. However, in these devices, the grating acts only as a passive optical scatterer, used to alter the light propagation path to overcome total internal reflection limitations. While it provides high light extraction efficiency, it does not change the radiative recombination rate of charge carriers within the tunneling light-emitting device, or the tunneling probability remains very low.

[0005] In recent years, some studies have proposed using metal nanoparticles or strips as top electrodes to enhance tunneling luminescence in tunneling light-emitting devices. For example, Novotny et al. proposed the concept of enhancing tunneling luminescence using optical antennas (Reference: M. Parzefall, et al., "Antenna-coupled tunnel junctions," Nature Nanotech. 10,1058 (2015)). They used gold (Au) nanoparticles or strips as the top electrode of the tunneling light-emitting device, utilizing localized surface plasmon resonances to enhance luminescence. However, such tunneling light-emitting devices are typically based on empirical geometric parameter scanning, failing to address the core contradictions at the microscale: the tunneling junction is a high-impedance source (typically with differential tunneling resistance on the order of MΩ), while the metallic nanoantenna is a low-impedance load (typically with equivalent radiation impedance on the order of Ω to kΩ), resulting in severe impedance mismatch; there is a timescale mismatch between the electron tunneling process (femtosecond level) and the photon radiation process (picosecond level), and the momentum mismatch between electrons and photons remains unresolved, leading to nonradiative recombination dominating. This severe impedance and momentum mismatch makes it difficult for electron energy to be effectively transferred to the radiation mode, resulting in extremely low energy transfer efficiency. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a tunneling light-emitting device based on barrier-mode field impedance matching that can achieve critical coupling between electron tunneling rate and optical mode radiation rate, thereby significantly improving electroluminescence efficiency and having high energy transmission efficiency.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a tunneling light-emitting device based on barrier-mode impedance matching, comprising a substrate, an insulating tunneling layer disposed on the substrate, and a metal nanoantenna array disposed on the insulating tunneling layer, wherein the metal nanoantenna array is a periodically arranged metal strip array; the geometric parameters of the metal nanoantenna array and the electrical parameters of the insulating tunneling layer are configured in a coordinated manner, such that under the bias voltage of the tunneling light-emitting device, the differential tunneling resistance of the insulating tunneling layer and the equivalent radiation impedance of the metal nanoantenna array at the excitation wavelength achieve conjugate matching or mode matching, so as to promote the efficient transfer of tunneling electron energy to the optical mode.

[0008] Compared with the prior art, the advantages of this invention are that by co-designing the geometric parameters of the metal nanoantenna array and the electrical parameters of the insulating tunneling layer, impedance matching is achieved between the insulating tunneling layer, which acts as a high impedance source, and the metal nanoantenna array, which acts as a low impedance load. This matching, on the one hand, synchronizes the electron tunneling rate with the plasmon oscillation rate, reduces energy reflection caused by impedance mismatch, and allows more tunneling electron energy to be coupled into the radiation mode of the metal nanoantenna array, rather than being dissipated as heat, thereby significantly improving energy transmission efficiency. On the other hand, the rate at which electron tunneling excites optical modes is optimized, achieving critical coupling between the electron tunneling rate and the optical mode radiation rate, thereby maximizing the electroluminescence external quantum efficiency of the tunneling light-emitting device.

[0009] Furthermore, the differential tunneling resistance of the insulating tunneling layer is denoted as... The magnitude of the equivalent radiation impedance of the metal nanoantenna array at the excitation wavelength is denoted as . , , express and The absolute value of the difference.

[0010] Furthermore, the metal strip is an inverted trapezoidal structure with a larger top and a smaller bottom. The contact edge between the metal strip and the insulating tunneling layer forms an acute angle, thereby forming a linear high-density tunneling current source. In the metal nanoantenna array, the metal strip is implemented using an inverted trapezoidal structure with a larger top and a smaller bottom, so that the contact edge between the metal strip and the insulating tunneling layer forms an acute angle. Based on the lightning rod effect, this acute angle region becomes a local electric field enhancement region. Under the bias voltage drive, the tunneling current density in this local electric field enhancement region is significantly higher than that in the central region of the metal strip. This allows the high-density tunneling electron flow to be precisely injected into the region with the strongest optical local state density in space, achieving maximum spatial overlap between carrier injection and optical mode field, thereby overcoming electron-photon momentum mismatch and achieving 100% spatial overlap efficiency.

[0011] Furthermore, the acute angle has a rounded corner with a radius of curvature R less than 10 nm, so as to form a "virtual needle tip" region at the acute angle, generating a strong local electric field enhancement effect, so that the tunneling current is highly concentrated in the "virtual needle tip" region.

[0012] Furthermore, the substrate is a heavily doped semiconductor substrate, preferably a heavily doped N-type silicon substrate with a resistivity of less than 0.005 Ω·cm, serving as a high-concentration electron source.

[0013] Furthermore, the insulating tunneling layer material is Al2O3, HfO2, or SiO2, and its thickness d ranges from 1.5 nm to 3.0 nm, to ensure that the tunneling light-emitting device operates under a mechanism dominated by direct quantum tunneling.

[0014] Furthermore, the metal strip is made of Ag, Au, Al, or Cu.

[0015] Furthermore, the period P of the metal nanoantenna array is 400-900 nm, and the duty cycle D is 0.4-0.8.

[0016] Furthermore, a modulation method for the tunneling light-emitting device based on barrier-mode impedance matching allows the tunneling light-emitting device to realize in-plane surface wave propagation mode and vertical free space radiation mode by applying a variable bias voltage between the metal nanoantenna array and the substrate.

[0017] Furthermore, when the bias voltage is within the first voltage range V1 to V2, the tunneling light-emitting device operates in an in-plane surface wave propagation mode; when the bias voltage is within the second voltage range V3 to V4 and V3 > V2, the tunneling light-emitting device operates in a vertical free-space radiation mode. The specific values ​​of the first voltage range V1 to V2 and the second voltage range V3 to V4 depend on the structural design, such as the thickness of the insulating tunneling layer, the material, the substrate doping concentration, and the geometric parameters of the metal nanoantenna array, and can be determined through simulation or experiment based on the specific tunneling light-emitting device structure. Attached Figure Description

[0018] Figure 1 is a schematic cross-sectional view of the overall structure of the tunneling light-emitting device of the present invention, showing the hierarchical relationship of the substrate, the insulating tunneling layer and the metal nanoantenna array and the annotation of key geometric dimensions; Figure 2 is a magnified schematic diagram of the contact area between a single metal strip and the insulating tunneling layer in Figure 1, highlighting the inverted trapezoidal cross-sectional features of the metal strip and the local field enhancement region located at the edge; Figure 3 is a three-dimensional perspective view of the tunneling light-emitting device of the present invention, showing that the metal nanoantenna array is arranged in a periodic strip shape; Figure 4 is a schematic diagram of the specific structural dimensions of the tunneling light-emitting device according to Embodiment 1 of the present invention; Figure 5 is an enlarged schematic diagram of the edge region of the metal strip in Figure 4, showing the acute angle characteristics and tunneling current distribution; Figure 6 is a schematic diagram of the working principle of the tunneling light-emitting device in the low-voltage mode according to Embodiment 2 of the present invention. The dashed arrows represent weaker tunneling currents, and the wavy arrows represent surface wave modes propagating along the interface. Figure 7 is a schematic diagram of the working principle of the tunneling light-emitting device in high voltage mode according to Embodiment 2 of the present invention. The solid arrows represent strong tunneling currents, and the wavy arrows represent free space radiation modes of vertical emission. Figure 8 This is a graph showing the variation of electroluminescence intensity with bias voltage (LV) of the tunneling light-emitting device in Embodiment 2 of the present invention under different detection methods; Figure 9 This is a comparison diagram of the far-field radiation angular distribution of the tunneling light-emitting device of Embodiment 2 of the present invention under different bias voltages (simulation experimental data). Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] Example 1: High-efficiency tunneling light-emitting device for the 1550 nm communication band This embodiment provides a specific tunneling light-emitting device optimized for C-band optical communication (center wavelength approximately 1550 nm).

[0021] like Figure 1 , Figure 4 As shown, a tunneling light-emitting device based on barrier-mode impedance matching includes a substrate 100, an insulating tunneling layer 200 disposed on the substrate 100, and a metal nanoantenna array 300 disposed on the insulating tunneling layer 200. The metal nanoantenna array 300 is a periodically arranged metal strip array. The geometric parameters of the metal nanoantenna array 300 and the electrical parameters of the insulating tunneling layer 200 are configured in a coordinated manner, so that under the bias voltage of the tunneling light-emitting device, the differential tunneling resistance of the insulating tunneling layer 200 and the equivalent radiation impedance of the metal nanoantenna array 300 at the excitation wavelength achieve conjugate matching or mode matching, so as to promote the efficient transfer of tunneled electron energy to the optical mode.

[0022] In this embodiment, the differential tunneling resistance of the insulating tunneling layer 200 is denoted as... The magnitude of the equivalent radiation impedance of the metal nanoantenna array 300 at the excitation wavelength is denoted as . , , express and The absolute value of the difference.

[0023] In this embodiment, the metal strip has an inverted trapezoidal structure that is wider at the top and narrower at the bottom. The contact edge between the metal strip and the insulating tunneling layer 200 forms an acute angle, thereby forming a linear high-density tunneling current source. The metal strip is made of silver (Ag).

[0024] In this embodiment, the substrate 100 is a heavily doped semiconductor substrate, preferably a heavily doped N-type silicon substrate with a resistivity of less than 0.005 Ω·cm, serving as a high-concentration electron source. The insulating tunneling layer 200 is an Al2O3 thin film grown on the surface of the substrate 100 using atomic layer deposition (ALD). The thickness d of the insulating tunneling layer 200 is precisely controlled to 2.2 nm ± 0.1 nm. This thickness ensures that the tunneling light-emitting device operates at its operating voltage using a direct quantum tunneling-dominated mechanism and is located in the region of strongest electroluminescence nonlinear response. For this embodiment, near the operating point of approximately 2.0 V, the differential tunneling resistance corresponding to this thickness is... Approximately 1×10 5 Ω·μm 2 The metal nanoantenna array 300 is formed by a periodic array of metal (Ag) strips on an insulating tunneling layer 200 through an electron beam evaporation and exfoliation process. The metal nanoantenna array 300 has a thickness h = 50 nm and a period P = 650 nm.

[0025] In this embodiment, as Figure 2 and Figure 5 As shown, each metal strip has an inverted trapezoidal cross-section. Its base width W bot 390 nm (duty cycle D = W) bot / P ≈ 0.6), top width W top Greater than the bottom width W bot This causes the contact edge between the metal strip and the insulating tunneling layer 200 to form an area of ​​approximately 70 degrees. ° The undercut angle θ. By controlling the rounded corner process, the contact edge between the metal strip and the insulating tunneling layer 200 forms an acute angle with a radius of curvature R of less than 10 nm. This geometric feature constitutes the "virtual needle tip 400".

[0026] The core of the tunneling light-emitting device based on barrier-mode impedance matching lies in matching the electrical characteristics of the insulating tunneling layer 200 with the optical characteristics of the metal nanoantenna array 300. The specific implementation steps are as follows: S1. Determine the differential tunneling resistance By fabricating planar control MIS junctions of different thicknesses d, their current-voltage (IV) characteristics were measured, and differential calculations were performed. Based on bias voltage V b Down, The correspondence between thickness d and thickness d.

[0027] S2. Determine the equivalent radiation impedance Z optA model of a 300-element metallic nanoantenna array was established using computational electromagnetic methods (such as the finite-difference time-domain method (FDTD) or the finite element method (FEM). Simulations were performed at its target operating wavelength λ to calculate its scattering parameters (S-parameters), which were then converted into equivalent input impedance, i.e., equivalent radiation impedance Z. opt .

[0028] S3. First, determine the initial range of the period P of the metal nanoantenna array based on the target wavelength λ. Then, iteratively adjust the insulating layer thickness d, the width W of the metal nanoantenna array, and the gap G between the metal strips until the matching condition is met. .

[0029] This embodiment of the tunneling light-emitting device based on barrier-mode impedance matching first involves fabricating planar reference MIS junctions of different thicknesses d, measuring their current-voltage (IV) characteristics, and then performing differential calculations. Based on bias voltage V b At approximately 2.0 V, The correspondence with thickness d. Then, using computational electromagnetic methods (such as the finite-difference time-domain method FDTD), an array with the above geometric parameters P=650 nm, W bot A metallic nanoantenna array model with a wavelength of 390 nm, an altitude of 50 nm, and Ag as the material is proposed. Simulations are performed at the target wavelength of 1550 nm to calculate its scattering parameters (S-parameters) and convert them to the equivalent input impedance Z. opt Finally, the results obtained from the experiment... (For d=2.2 nm) and |Z obtained from simulation opt Substituting into the impedance matching criterion formula: Calculations show that the parameter combination in this embodiment satisfies this condition, indicating that the differential tunneling resistance of the insulating tunneling layer 200 is... The equivalent radiation impedance Z of the metal nanoantenna array 300 opt Conjugate matching was achieved, laying the foundation for efficient energy transfer.

[0030] The working condition and technical effect of the tunneling light-emitting device based on barrier-mode impedance matching in this embodiment: A bias voltage V of 2.0 V is applied between the two ends of the fabricated tunneling light-emitting device (metal nanoantenna array 300 and substrate 100). b Due to the impedance matching design and the strong local electric field enhancement effect generated by the "virtual tip 400" at the edge of the inverted trapezoidal antenna (… Figure 5In the "virtual needle tip 400" region, the tunneling current is highly concentrated in this acute-angled area, and its current density can be several orders of magnitude higher than that in the central region of the strip. The high-density tunneling electron flow is precisely injected into the same region with the strongest optical local state density in space, achieving nearly 100% carrier-optical field spatial overlap and effectively overcoming momentum mismatch.

[0031] Therefore, the surface plasmon modes excited by the tunneling light-emitting device can be efficiently scattered by the metal nanoantenna array 300 into free-space light perpendicular to the substrate 100. Far-field spectroscopy measurements revealed that the tunneling light-emitting device emits a strong electroluminescent signal with a center wavelength of approximately 1550 nm. Preliminary experiments show that, under this optimized design, the external quantum efficiency (EQE) of the tunneling light-emitting device can be improved by more than two orders of magnitude compared to the traditional unmatched planar MIS tunnel junction structure, and exhibits superlinear growth characteristics with injection current (or bias voltage).

[0032] Example 2: Voltage-regulated dual-mode light-emitting device and its modulation method This embodiment aims to demonstrate that the tunneling light-emitting device based on barrier-mode impedance matching, as described in Embodiment 1, can achieve dynamic switching of light emission modes through simple electrical control, thereby expanding its application functions.

[0033] like Figure 6 , Figure 7 , Figure 8 and Figure 9 As shown, a modulation method for a tunneling light-emitting device based on barrier-mode field impedance matching is achieved by controlling the bias voltage V applied between the metal nanoantenna array 300 and the substrate 100. b The size of the device allows the same tunneling light-emitting device to operate in two distinct optical modes: I. In-plane surface wave propagation mode (applicable to on-chip optical interconnects): Operation: Set the bias voltage V b Set and maintain the voltage within the first voltage range, for example, 1.2 V to 1.5 V.

[0034] Principles and verification: such as Figure 6 As shown, at this voltage, the electron energy is relatively low, primarily exciting the SPP mode confined to the interface, which propagates along the plane as a surface wave. A stronger signal (corresponding to...) can be detected using an integrated waveguide. Figure 8 (dashed curve), while the far-field measurement signal is extremely weak ( Figure 9 The dotted line in the middle confirms that energy is localized on the surface, which is suitable for on-chip optical interconnects.

[0035] II. Vertical Free Space Radiation Mode (Applicable to inter-chip or board-level optical interconnects): Operation: Set the bias voltage V bIncrease to the second voltage range, for example, greater than 2.0 V (typical operating value is 2.5 V).

[0036] Principles and verification: such as Figure 7 As shown, at higher voltages, electron energy increases, and the excited SPP mode can be phase-matched and scattered into vertical radiation by the 300-element metal nanoantenna array. Strong outgoing light (corresponding to...) can be collected through the upper objective lens. Figure 8 (Solid line curve), the far-field angular distribution exhibits a sharp radiation peak in the 0° direction ( Figure 9 (Solid line in the middle) enables high-quality directional emission, suitable for inter-chip or board-level optical interconnects.

[0037] The key advantage of this embodiment lies in its revelation and utilization of an inherent characteristic of the tunneling light-emitting device of the present invention—the dependence of the emission mode on the bias voltage. This allows a single tunneling light-emitting device to adaptively reconfigure between two important functions—"on-chip surface waveguide communication" and "inter-chip free-space interconnection"—by changing a simple electrical parameter (DC voltage) according to system requirements. This functionality is unattainable by traditional light-emitting diodes (LEDs) or fixed-function tunneling light sources, greatly enhancing the flexibility and functional density of integrated photonic systems.

Claims

1. A tunneling light-emitting device based on barrier-mode impedance matching, comprising a substrate, an insulating tunneling layer disposed on the substrate, and a metal nanoantenna array disposed on the insulating tunneling layer, wherein the metal nanoantenna array is a periodically arranged metal strip array; characterized in that, The geometric parameters of the metal nanoantenna array and the electrical parameters of the insulating tunneling layer are configured in a coordinated manner, such that under the bias voltage of the tunneling light-emitting device, the differential tunneling resistance of the insulating tunneling layer and the equivalent radiation impedance of the metal nanoantenna array at the excitation wavelength achieve conjugate matching or modulus matching, thereby promoting the efficient transfer of tunneling electron energy to the optical mode.

2. The tunneling light-emitting device based on barrier-mode impedance matching according to claim 1, characterized in that, The differential tunneling resistance of the insulating tunneling layer is denoted as... The magnitude of the equivalent radiation impedance of the metal nanoantenna array at the excitation wavelength is denoted as . , , express and The absolute value of the difference.

3. The tunneling light-emitting device based on barrier-mode impedance matching according to claim 1, characterized in that, The metal strip has an inverted trapezoidal structure that is larger at the top and smaller at the bottom. The contact edge between the metal strip and the insulating tunneling layer forms an acute angle, thereby forming a linear high-density tunneling current source.

4. The tunneling light-emitting device based on barrier-mode impedance matching according to claim 3, characterized in that, The acute angle has a rounded corner with a radius of curvature R less than 10 nm, so as to form a "virtual needle tip" region at the acute angle, generating a strong local electric field enhancement effect, so that the tunneling current is highly concentrated in the "virtual needle tip" region.

5. The tunneling light-emitting device based on barrier-mode impedance matching according to claim 1, characterized in that, The substrate is a heavily doped semiconductor substrate, preferably a heavily doped N-type silicon substrate with a resistivity of less than 0.005 Ω·cm, serving as a high-concentration electron source.

6. The tunneling light-emitting device based on barrier-mode impedance matching according to claim 1, characterized in that, The insulating tunneling layer material is Al2O3, HfO2, or SiO2, and its thickness d ranges from 1.5 nm to 3.0 nm to ensure that the tunneling light-emitting device operates under a mechanism dominated by direct quantum tunneling.

7. The tunneling light-emitting device based on barrier-mode impedance matching according to claim 1, characterized in that, The metal strip is made of Ag, Au, Al or Cu.

8. The tunneling light-emitting device based on barrier-mode impedance matching according to claim 1, characterized in that, The period P of the metal nanoantenna array is 400-900 nm, and the duty cycle D is 0.4-0.

8.

9. A modulation method for a tunneling light-emitting device based on barrier-mode field impedance matching as described in any one of claims 1 to 8, characterized in that, By applying a variable bias voltage between the metal nanoantenna array and the substrate, the tunneling light-emitting device can realize in-plane surface wave transmission mode and vertical free space radiation mode.

10. The modulation method for a tunneling light-emitting device based on barrier-mode field impedance matching according to claim 9, characterized in that, When the bias voltage is in the first voltage range V1 to V2, the tunneling light-emitting device operates in the in-plane surface wave transmission mode; when the bias voltage is in the second voltage range V3 to V4 and V3 > V2, the tunneling light-emitting device operates in the vertical free space radiation mode.

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