A single photon detector based on dynamic regulation of surface acoustic wave

Abstract

The application relates to a single-photon detector based on dynamic regulation of a surface acoustic wave technology and belongs to the technical field of photoelectric detection. The single-photon detector is an ultra-sensitive photoelectric conversion device capable of responding to the energy of a single photon and has important applications in the fields of quantum communication, fluorescence lifetime microscopic imaging and large-scale integrated circuit detection. Traditional single-photon detectors usually rely on the carrier generated by an avalanche effect to realize single-photon response in static electric field transportation, but the performance is limited by the problems of insufficient dark current suppression capability and regulation flexibility. The application introduces a dynamic piezoelectric field generated by a surface acoustic wave to realize dynamic and flexible regulation of the electric field distribution and carrier transportation of the single-photon detector to control the dark current.

Description

Technical Field

[0001] This invention relates to a single-photon detector based on surface acoustic wave technology with dynamic control, belonging to the field of photoelectric detection technology. Background Technology

[0002] Single-photon detectors are ultrasensitive photoelectric conversion devices capable of responding to the energy of a single photon, and they have important applications in quantum communication, fluorescence lifetime microscopy, and large-scale integrated circuit detection. Traditional single-photon detectors based on single-photon avalanche diodes (SPADs) amplify single-photon signals by applying a reverse bias voltage higher than the breakdown voltage (this mode is called Geiger mode) to the semiconductor junction region, utilizing the carrier avalanche multiplication effect. For example, after an InGaAs / InP SPAD absorbs a photon in Geiger mode, the photons generated in the absorption layer excite carriers, which, under the influence of an electric field, enter the multiplication layer, triggering an avalanche current and forming a macroscopic pulse. A significant current can then be detected through electrodes. Traditional single-photon detectors typically rely on the transport of carriers generated by the avalanche effect in a static electric field to achieve a single-photon response, but their performance is limited by issues such as dark current suppression capability and insufficient modulation flexibility.

[0003] Surface acoustic wave (SAW) devices are electronic components based on the properties of piezoelectric materials. Their core working principle involves signal processing through the interconversion of electrical signals and mechanical acoustic waves. When an alternating electrical signal is applied to the interdigital transducer (IDT) of the device, the piezoelectric material (such as quartz or lithium niobate) undergoes periodic mechanical deformation due to the inverse piezoelectric effect, thereby exciting surface acoustic waves (Rayleigh waves) propagating in a specific direction on the material surface. The energy is concentrated within a depth of approximately one wavelength below the surface, and the propagation speed is typically 3000 to 5000 meters per second. During propagation, this acoustic wave carries a periodically changing stress field and piezoelectric field. If the acoustic wave encounters a reflector grating or another IDT during propagation, it is converted back into an electrical signal through the direct piezoelectric effect. The frequency of the acoustic wave is determined by the spacing (wavelength) of the IDT electrodes and the sound velocity of the material, using the formula f = v / λ, where v is the sound velocity and λ is the electrode period. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to control the dark current by introducing a dynamic piezoelectric field generated by surface acoustic waves to achieve dynamic and flexible control of the electric field distribution and carrier transport of a single-photon detector.

[0005] To achieve the above and other related objectives, the technical solution provided by this invention is as follows.

[0006] This technology integrates surface acoustic wave devices and single-photon avalanche diode devices.

[0007] Both devices were fabricated on the same lithium niobate substrate.

[0008] The surface acoustic wave (SAW) device on a lithium niobate substrate comprises four pairs of interdigitated electrodes in the top, bottom, left, and right directions. The width, length, distance, and thickness of the four pairs of interdigitated electrodes are consistent, and the distance between the interdigits is consistent with the width of the interdigits themselves. The distances between the top, bottom, left, and right interdigitated electrodes are integer multiples of the width of the interdigits.

[0009] The single-photon avalanche diode device is disposed on the top of the surface acoustic wave structure substrate and in the middle of the four pairs of interdigitated electrodes.

[0010] Optionally, the single-photon avalanche diode structure includes:

[0011] The substrate is shared with the surface acoustic wave structure.

[0012] The lower contact layer is disposed directly above the substrate;

[0013] A buffer layer is disposed on the lower contact layer;

[0014] The lower electrode is disposed on the portion of the lower contact layer that is exposed outside the buffer layer;

[0015] An absorption layer is placed on top of the buffer layer;

[0016] A gradient layer is applied over the absorption layer;

[0017] A charge layer is placed on the gradient layer;

[0018] A multiplication layer is placed on top of the charge layer;

[0019] The upper contact layer is positioned on the multiplication layer;

[0020] An anti-reflective entrance window is installed on the upper contact layer;

[0021] The upper electrode is located in the area of ​​the upper contact layer that is not covered by the anti-reflective entry window. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the integrated surface acoustic wave and single-photon avalanche diode device of the present invention.

[0023] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of a surface acoustic wave device.

[0024] Figure 3 for Figure 1 A schematic diagram of the interdigitated electrode distribution of a surface acoustic wave device.

[0025] Figure 4 for Figure 1 A schematic diagram of the structure of a single-photon avalanche diode device. Detailed Implementation

[0026] Two devices are fabricated on the same lithium niobate substrate. Applying a high-frequency AC signal to the surface acoustic wave (SAW) device excites a periodic piezoelectric field and a stress field propagating along the substrate surface. When these two fields propagate to the single-photon detector, they alter the electric field structure and carrier transport efficiency of its internal material, thereby changing the tunneling current and enabling the SAW technology to modulate the performance of the single-photon detector. This technology employs four pairs of SAW interdigitated electrodes (top, bottom, left, and right) to achieve the superposition of up to four sets of SAW waves. By changing the number and direction of the initiating SAW waves, the operating power of the SAW device, and the frequency and phase of the applied AC signal, the periodic piezoelectric field and stress field propagating along the substrate surface can be altered, thus dynamically controlling the single-photon detector.

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] Please see Figures 1 to 4 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show components relevant to the present invention and are not drawn according to the actual number, shape, and size of the components in implementation. In actual implementation, the form, quantity, and proportion of each component can be arbitrarily changed, and the component layout may be more complex. The structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effects and objectives of the present invention, should still fall within the scope of the technical content disclosed in the present invention.

[0029] First, such as Figure 1 As shown, the present invention provides a single-photon detector based on dynamic modulation of surface acoustic waves, which includes: a surface acoustic wave structure 1, comprising a substrate 100 and left and right interdigital electrodes 101 and 102; and a single-photon avalanche diode structure 2, disposed at the middle position on the substrate of the surface acoustic wave device.

[0030] like Figure 2 and Figure 3As shown, the surface acoustic wave (SAW) device has four pairs of interdigitated electrodes: 101, 102, 103, and 104. The width of the interdigitated electrodes is d, and the period of the SAW wave is λ = 4d. Based on the selected substrate material (e.g., lithium niobate), the velocity v of the sound wave propagating on its surface is found, and the frequency f of the applied alternating current is determined using the formula f = v / λ.

[0031] After determining the operating parameters of the surface acoustic wave (SAW), an AC voltage of the same frequency and phase is simultaneously applied to all four pairs of interdigitated electrodes. This results in a SAW peak forming at the center of the substrate. The intensity of this peak depends on the applied voltage. A stronger SAW peak carries a stronger piezoelectric and stress field, thus significantly altering the electric field distribution within the single-photon avalanche diode above the substrate, thereby changing the tunneling current intensity and reducing the dark current. By changing the phase of the applied AC voltage, the intensity and position of the SAW peak can be adjusted, thereby changing the electric field distribution within the single-photon avalanche diode.

[0032] In an optional embodiment of the present invention, such as Figure 4 As shown, the single-photon avalanche photodiode structure 2 includes:

[0033] Substrate 100 shares the same substrate as the surface acoustic wave structure;

[0034] The lower contact layer 201 is disposed directly above the substrate;

[0035] Buffer layer 203 is disposed on the lower contact layer;

[0036] The lower electrode 202 is disposed on the portion of the lower contact layer exposed outside the buffer layer;

[0037] Absorbent layer 204 is disposed on the buffer layer;

[0038] Gradient layer 205 is disposed on the absorption layer;

[0039] The charge layer 206 is disposed on the gradient layer;

[0040] Multiplication layer 207 is disposed on the charge layer;

[0041] The upper contact layer 208 is disposed on the multiplication layer;

[0042] The upper electrode 209 is located in the area of ​​the upper contact layer that is not covered by the anti-reflective entrance window.

[0043] An anti-reflective entrance window 210 is installed on the upper contact layer;

[0044] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A single-photon detector based on dynamic modulation of surface acoustic waves, characterized in that, include: The surface acoustic wave structure comprises a lithium niobate substrate and four pairs of interdigitated electrodes. A single-photon avalanche diode structure is disposed on the top of the surface acoustic wave structure substrate and in the middle of the four pairs of interdigitated electrodes.

2. The single-photon detector based on dynamic modulation of surface acoustic waves according to claim 1, characterized in that, The width, length, distance, and thickness of the four pairs of interdigitated electrodes in the surface acoustic wave structure are consistent, and the distance between the interdigitated electrodes is consistent with the width of the interdigitated electrodes themselves. The distance between the top and bottom and left and right interdigitated electrodes is an integer multiple of the width of the interdigitated electrode.

3. The single-photon detector based on dynamic modulation of surface acoustic waves according to claim 1, characterized in that, The single-photon avalanche photodiode structure includes: The substrate is shared with the surface acoustic wave structure. The lower contact layer is disposed directly above the substrate; A buffer layer is disposed on the lower contact layer; The lower electrode is disposed on the portion of the lower contact layer that is exposed outside the buffer layer; An absorption layer is placed on top of the buffer layer; A gradient layer is applied over the absorption layer; A charge layer is placed on the gradient layer; A multiplication layer is placed on top of the charge layer; The upper contact layer is positioned on the multiplication layer; An anti-reflective entrance window is installed on the upper contact layer; The upper electrode is located in the area of ​​the upper contact layer that is not covered by the anti-reflective entry window.

4. The single-photon detector based on dynamic modulation of surface acoustic waves according to claim 3, characterized in that, The lower and upper electrodes of the single-photon avalanche photodiode structure are ring structures.

5. The single-photon detector based on dynamic modulation of surface acoustic waves according to any one of claims 1 or 3, characterized in that, In the single-photon avalanche diode structure, the diameter of the lower contact layer is less than the width of two interdigitated fingers, and the diameter of the remaining layers is less than the diameter of the contact layer.

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