Field-effect superconducting Josephson junction device and preparation method thereof

Abstract

The present invention provides a field-effect superconducting Josephson junction device and its fabrication method. The field-effect superconducting Josephson junction device comprises: a substrate, a left-bank electrode of a bridge junction, a right-bank electrode of a bridge junction, an insulating channel, a nanobridge, an insulating dielectric layer, and a voltage electrode. The insulating channel isolates the left-bank electrode and the right-bank electrode of the bridge junction from each other. The nanobridge spans the insulating channel to connect the left-bank electrode and the right-bank electrode of the bridge junction. The insulating dielectric layer covers the nanobridge. The voltage electrode is located on the upper side of the insulating dielectric layer and applies a modulated electric field to the nanobridge. The field-effect superconducting Josephson junction device and its fabrication method provided by the present invention can solve the problem that existing Josephson field-effect transistors (FETs) have too low a critical current and too low an operating temperature, making them unsuitable for use in superconducting integrated circuits.

Description

Technical Field

[0001] The present invention relates to the field of superconducting electronics, in particular to a field effect superconducting Josephson junction device and a preparation method thereof. Background Art

[0002] In semiconductor integrated circuit technology, field-effect transistors are the fundamental unit of all logic circuits. Field effect transistors control the conductivity of a device by applying an electric field. The concentration of carriers in the semiconductor material allows the electric field to pass through, thereby controlling the carrier concentration.

[0003] However, the carriers in superconducting materials exist in the form of electron Cooper pairs, and their distribution decays exponentially from the surface to the interior of the superconductor. The superconducting penetration depth is very small. Therefore, it is very difficult to directly control the carrier concentration inside the superconductor through the electric field in theory.

[0004] The basic component of a superconducting integrated circuit is a Josephson junction. The phase difference between the current flowing through a superconducting Josephson junction and the superconducting wave function at both ends of the junction is in the form of a sinusoidal function. This effect is called the DC Josephson effect.

[0005] Superconducting Josephson junctions, similar to PN junctions in semiconductor integrated circuits, are key components of superconducting integrated circuits. Currently, the control gates of these Josephson junctions control the phase of the junction through current-magnetic field coupling, thereby controlling the current. This design of control gates occupies a large area, posing a significant challenge to the miniaturization of superconducting circuits. Therefore, superconducting Josephson junctions with electric field effects could significantly simplify the complexity of superconducting integrated circuit design and improve the overall integration of the circuits.

[0006] To address this problem of electric field regulation, as early as the 1960s, scientists attempted to control supercurrents in a superconductor-normal metal-superconductor Josephson junction (SNS) structure. This control was achieved by applying a voltage to the normal metal layer to modify the quasiparticle distribution. Another technique for controlling Josephson supercurrents is to introduce a semiconductor nanowire whose carrier concentration can be adjusted by an electric field effect. This Josephson field-effect transistor is achieved by constructing a small hybrid superconductor-semiconductor structure.

[0007] Although the field effect in this hybrid semiconductor-superconductor structure is consistent with theoretical predictions and has been confirmed experimentally, the critical current of the hybrid semiconductor-superconductor Josephson junction is at the nanoampere level, and the ambient temperature required for operation is below 3K. The critical current and operating temperature of this structure are too low, making it unsuitable for use in superconducting integrated circuits. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a field-effect superconducting Josephson junction device and a preparation method thereof, which are used to solve the problems of the existing Josephson field-effect transistor having too low critical current and too low operating temperature, and being unable to be used in superconducting integrated circuits.

[0009] To achieve the above-mentioned and other related purposes, the present invention provides a field-effect superconducting Josephson junction device comprising:

[0010] Substrate, bridge junction left bank electrode, bridge junction right bank electrode, insulating channel, nanobridge, insulating dielectric layer and voltage electrode;

[0011] The bridge junction left bank electrode, the insulating trench and the bridge junction right bank electrode are located on the upper side of the substrate, and the insulating trench isolates the bridge junction left bank electrode and the bridge junction right bank electrode from each other;

[0012] The nanobridge spans the insulating trench to connect the left-bank electrode of the bridge junction with the right-bank electrode of the bridge junction, and is located at least on a portion of the upper surface of the left-bank electrode of the bridge junction and a portion of the upper surface of the right-bank electrode of the bridge junction;

[0013] The insulating dielectric layer covers the nanobridge and is arranged on the upper side of the bridge junction left bank electrode, the insulating channel and the bridge junction right bank electrode;

[0014] The voltage electrode is located on the upper side of the insulating dielectric layer, and in a top view direction, the projection of the voltage electrode at least covers the overlapping area of ​​the nanobridge and the insulating channel.

[0015] Optionally, the thickness of the nanobridge is smaller than the thickness of the left-bank electrode of the bridge junction, and is also smaller than the thickness of the right-bank electrode of the bridge junction.

[0016] Optionally, the field-effect superconducting Josephson junction device further includes an isolation layer, which is located on the upper side of the substrate and on the lower side of the bridge junction right-bank electrode, isolating the bridge junction right-bank electrode from the substrate.

[0017] Optionally, the bridge length of the nanobridge is smaller than the coherence length of the superconducting material used for the nanobridge.

[0018] Optionally, the thickness of the nanobridge is smaller than the penetration depth of the superconducting material used for the nanobridge.

[0019] Optionally, the nanobridge, the bridge junction left bank electrode and the bridge junction right bank electrode use the same superconducting material.

[0020] Optionally, the material of the substrate includes at least one of MgO, sapphire, Si3N4, Al2O3 and SiO2; the material of the left-bank electrode of the bridge includes at least one of Nb, NbN, NbTi and NbTiN; the material of the right-bank electrode of the bridge includes at least one of Nb, NbN, NbTi and NbTiN.

[0021] Optionally, the critical current of the field effect superconducting Josephson junction device is changed by adjusting the voltage of the voltage electrode;

[0022] By the formula θ=arcsin(I C / I S )+2πL J I S / Ф0, modulates the current-phase relationship of the field-effect superconducting Josephson junction device, where I C Expressed as the critical current, I S is represented by the superconducting current of the field effect superconducting Josephson junction device, θ is represented by the phase difference between the wave function in the left bank electrode of the bridge junction and the wave function in the right bank electrode of the bridge junction, L J It represents the equivalent inductance of the field effect superconducting Josephson junction device, and Φ0 represents a magnetic flux quantum.

[0023] The present invention also provides a method for preparing a field-effect superconducting Josephson junction device, the method comprising:

[0024] S1), providing a substrate, and forming a first superconducting material layer on the upper surface of the substrate;

[0025] S2), forming a patterned mask layer on the upper surface of the first superconducting material layer, and etching the first superconducting material layer based on the mask layer to form a bridge junction left bank electrode, a bridge junction right bank electrode and a trench, wherein the trench is located between the bridge junction left bank electrode and the bridge junction right bank electrode;

[0026] S3), filling the trench to form an insulating trench;

[0027] S4), forming a nanobridge on the upper surfaces of the bridge junction left bank electrode, the insulating trench, and the bridge junction right bank electrode, wherein the nanobridge spans the insulating trench to connect the bridge junction left bank electrode and the bridge junction right bank electrode;

[0028] S5), forming an insulating dielectric layer on the upper surfaces of the nanobridge, the bridge junction left bank electrode, the insulating trench and the bridge junction right bank electrode;

[0029] S6), forming a voltage electrode on the upper surface of the insulating dielectric layer, wherein, in a top view, a projection of the voltage electrode at least covers an overlapping area of ​​the nanobridge and the insulating channel.

[0030] Optionally, the thickness of the nanobridge is smaller than the thickness of the first superconducting material layer.

[0031] As described above, the field-effect superconducting Josephson junction device of the present invention and the preparation method thereof isolate the left-bank electrode and the right-bank electrode of the bridge junction through an insulating trench, realize a weak connection between the left-bank electrode and the right-bank electrode of the bridge junction through a nanobridge, apply an electric field through a voltage electrode above the nanobridge to change the critical current of the junction to obtain a large critical current, and the thinner nanobridge and the thicker left-bank electrode and right-bank electrode of the bridge junction are located in different structural layers, which can enable the device to have a current-phase relationship with better nonlinearity. At the same time, the nanobridge also uses superconducting materials, which can ensure that the operating temperature of the device is equivalent to the operating temperature of the left (or right) bank superconducting electrode, so that the operating temperature is not too low. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Shown is a front view structural schematic diagram of the field effect superconducting Josephson junction device of the present invention.

[0033] Figure 2 Shown is a schematic diagram of the top view of the field effect superconducting Josephson junction device of the present invention.

[0034] Figure 3 The schematic diagram shows the front view of the device structure in which the contact area between the nanobridge and the left bank electrode of the bridge junction described in Example 1 is larger.

[0035] Figure 4 Shown is a front view structural schematic diagram of a field effect superconducting Josephson junction device with an isolation layer according to the present invention.

[0036] Figure 5 Shown is a schematic diagram of the three-dimensional structure of the 2D nanobridge Josephson junction described in Example 1.

[0037] Figure 6 Shown is an electron microscope image of the field-effect superconducting Josephson junction device described in the present invention.

[0038] Figure 7 Shown is a functional relationship diagram of the critical current and voltage of the field effect superconducting Josephson junction device of the present invention.

[0039] Figure 8 Shown is a current-phase relationship diagram of the field effect superconducting Josephson junction device of the present invention at different voltages.

[0040] Figure 9 Shown is a front view structural schematic diagram of a field effect superconducting Josephson junction device after trench formation according to the present invention.

[0041] Figure 10Shown is a schematic front view of the structure of a field effect superconducting Josephson junction device after forming a nanobridge according to the present invention.

[0042] Component number description

[0043] 10 Field-effect superconducting Josephson junction devices

[0044] 110 substrate

[0045] 120 Bridge junction left bank electrode

[0046] 130 Bridge junction right bank electrode

[0047] 140 Insulation Trench

[0048] 141 Groove

[0049] 150 nanometer bridge

[0050] 151 Two-Dimensional Nanobridge

[0051] 160 Insulation dielectric layer

[0052] 170 voltage pole

[0053] 180 Isolation Layer DETAILED DESCRIPTION

[0054] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0055] See also Figures 1 to 10 It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0056] Example 1

[0057] This embodiment provides a field effect superconducting Josephson junction device 10, such as Figure 1 、 Figure 2 and Figure 6 As shown, the field effect superconducting Josephson junction device 10 includes:

[0058] The substrate 110 is made of at least one of MgO, sapphire, Si3N4, Al2O3 and SiO2.

[0059] The bridge left bank electrode 120, the bridge right bank electrode 130 and the insulating channel 140 are formed on the upper side of the substrate 110. The insulating channel 140 isolates the bridge left bank electrode 120 and the bridge right bank electrode 130 from each other. The bridge left bank electrode 120 and the bridge right bank electrode 130 serve as two superconductors of the Josephson junction respectively. The materials of the bridge left bank electrode 120 and the bridge right bank electrode 130 include but are not limited to at least one of Nb, NbN, NbTi, and NbTiN, and the materials of the bridge left bank electrode 120 and the bridge right bank electrode 130 can be different.

[0060] The nanobridge 150 is located on the upper side of the left-bank bridge electrode 120, the insulating channel 140 and the right-bank bridge electrode 130, spanning the insulating channel 140 to connect the left-bank bridge electrode 120 with the right-bank bridge electrode 130, forming a weak connection between the two superconductors (the left-bank bridge electrode 120 and the right-bank bridge electrode 130), wherein the materials used for the nanobridge 150 include but are not limited to Nb, NbN, NbTi, and NbTiN.

[0061] The insulating dielectric layer 160 is located on the upper side of the bridge left bank electrode 120, the insulating channel 140 and the bridge right bank electrode 130, and covers the nanobridge 150, protecting and electrically isolating the nanobridge 150, wherein the material used for the insulating dielectric layer 160 includes but is not limited to at least one of a SiO2 layer, a HfO2 layer or an Al2O3 layer.

[0062] The voltage electrode 170 is located on the upper side of the insulating dielectric layer 160 , and the electric field formed therein applies a modulated electric field to the nanobridge through the insulating dielectric layer 160 , thereby changing the critical current of the Josephson junction.

[0063] In this embodiment, the nanobridge 150 is formed on the upper surface of two superconductors (the bridge left bank electrode 120 and the bridge right bank electrode 130), and its thickness is much smaller than the thickness of the bridge left bank electrode 120 (or the bridge right bank electrode 130). Since the thickness of the nanobridge 150 can be thinner than the bridge left bank electrode 120 (or the bridge right bank electrode 130), for example, its thickness is smaller than the penetration depth of the superconducting material used, the modulated electric field applied by the voltage electrode 170 can effectively penetrate the nanobridge 150 to achieve effective modulation of the critical current of the Josephson junction; at the same time, Figure 5 As shown in the figure, it is a schematic diagram of the conventional 2D nanobridge Josephson junction structure. In the structure, since the 2D nanobridge and the two superconductors are in the same structural layer, the thickness of the 2D nanobridge and the two superconductors are similar. Figure 3When the two-dimensional nanobridge Josephson junction shown is used to prepare a field-effect superconducting Josephson junction device, the modulated electric field applied by the voltage electrode 170 cannot effectively penetrate the two-dimensional nanobridge, and thus cannot effectively modulate the critical current of the Josephson junction through voltage. Moreover, it is also impossible to ensure that the relationship between the wave function phase difference at both ends of the junction and the superconducting current (current-phase relation, CPR) is a nonlinear relationship. However, the nanobridge 150 in the present application spans the insulating channel 140 to connect the two superconductors to form a three-dimensional nanobridge Josephson junction. Compared with the two-dimensional nanobridge Josephson junction, when the bridge length L is the same, it has a better current-phase relationship (only slightly deviates from the sine function curve).

[0064] In some embodiments, as Figure 1 As shown, the upper surface of the insulating trench 140, the upper surface of the bridge junction left bank electrode 120 and the upper surface of the bridge junction right bank electrode 130 are flush with each other; in this embodiment, controlling the upper surfaces of the insulating trench 140, the bridge junction left bank electrode 120 and the bridge junction right bank electrode 130 to be flush with each other helps to control the bridge length of the nanobridge 150 spanning the bridge junction left bank electrode 120 and the bridge junction right bank electrode 130. The bridge length L of the nanobridge 150 will affect the current-phase relationship of the Josephson junction. According to the DC Josephson equation I C =I S From sin(θ), it can be seen that the current-phase relationship is sinusoidal, but this sinusoidal relationship only exists when the bridge length (L) of the nanobridge 150 is less than the coherence length (ξ) of the superconducting material. When L / ξ is greater than 1, the current-phase relationship of the Josephson junction will gradually deviate from the sinusoidal function. Therefore, preferably, the bridge length L of the nanobridge 150 is less than the coherence length of the superconducting material used in the nanobridge.

[0065] In some embodiments, as Figure 2 As shown, since the bridge length L and width of the nanobridge 150 are respectively determined by the thickness of the insulating channel 140 and the width of a section of the nanobridge 150 covering the insulating channel 140, in order to make the two ends of the nanobridge 150 form good contact with the bridge left bank electrode 120 and the bridge right bank electrode 130 respectively, the area where the two ends of the nanobridge 150 contact the bridge left bank electrode 120 and the bridge right bank electrode 130 does not need to be limited by the width and length of the nanobridge 150, and can be made wider to make the contact area larger.

[0066] In some embodiments, as Figure 4As shown, the field effect superconducting Josephson junction device 10 also includes an isolation layer 170, which is located on the upper side of the substrate 110 and on the lower side of the bridge right bank electrode 130, isolating the bridge right bank electrode 130 from the substrate 110; since the thickness of the insulating channel 140 determines the bridge length L of the nanobridge 150, in order to make the bridge length L of the nanobridge 150 less than the coherence length (ξ) of the superconducting material used in the nanobridge, the thickness of the insulating channel 140 should also be less than the coherence length (ξ) of the superconducting material used in the nanobridge, and when some superconducting materials with extremely short coherence lengths are used, it may even be less than 10 nm. Therefore, considering the difficulty of implementing the preparation process, in some process paths, after the bridge left bank electrode is formed, the insulating channel 140 is deposited on its sidewall to form the isolation layer 170, and then the bridge right bank electrode is prepared.

[0067] In some embodiments, in order to effectively and sensitively control the critical current of the Josephson junction, the thickness of the nanobridge 150 is smaller than the penetration depth of the superconducting material used in the nanobridge to ensure that the electric field can enter the nanobridge 150 and act on the Cooper pairs.

[0068] In some embodiments, the superconducting material used for the left-bank bridge electrode 120 and the right-bank bridge electrode 130 is the same, so that the two have the same critical current under the same structural morphology and environmental conditions; in some embodiments, the superconducting material used for the left-bank bridge electrode 120, the right-bank bridge electrode 130 and the nanobridge 150 is the same, so that the three have the same operating temperature. For example, Nb is used, and its superconducting critical temperature is about 9K. Devices based on Nb superconducting materials can operate in a liquid helium environment, and the operating temperature conditions are easier to achieve. In addition, the penetration depth of Nb superconducting materials is higher than that of other superconducting metals, and the critical current of the Josephson junction can be effectively controlled by the electric field formed by the voltage electrode 170.

[0069] In order to further illustrate the beneficial effects of the field-effect superconducting Josephson junction device 10 described in this embodiment, this embodiment also illustrates the working conditions of the field-effect superconducting Josephson junction device 10:

[0070] When the field effect superconducting Josephson junction device 10 is working, the voltage electrode 170 applies a voltage to form an electric field acting on the nanobridge 150, and the superconducting critical current I of the field effect superconducting device 10 is changed by adjusting the amplitude of the voltage. C size.

[0071] Specifically, such as Figure 7 As shown, when a voltage V is applied to the voltage electrode 170 gate When the critical current of the Josephson junction isC It will be regulated by voltage within a certain voltage range. When the applied voltage is small, the critical current I C There will be no change when the applied voltage V gate Exceeds a certain threshold range (such as V g1 ), the Josephson critical current I C Will be gradually suppressed to zero, where I C0 Expressed as the maximum critical current of the field effect superconducting Josephson junction device; voltage V gate =V g1 When I C =I C0 Voltage V gate =V g2 When I C =3I C0 / 4; voltage V gate =V g3 When I C =I C0 / 2; voltage V gate =V g4 When I C =I C0 / 4, statistical critical current I C With V gate The relationship between the Josephson junction and the voltage can be obtained by C =I C0 f(V gate ).

[0072] In actual operation, it is hoped that the critical current I C The device conducts a larger current, but at the same time, it is also desired to obtain a better current-phase relationship (a current-phase relationship with better nonlinearity). In order to better demonstrate the current-phase relationship of the field-effect superconducting Josephson junction device 1 of this embodiment, the field-effect superconducting Josephson junction device 1 is understood as a physical model, which is composed of an ideal Josephson junction (no inductance) and an equivalent inductance (the inductance of the field-effect superconducting Josephson junction device 10) in series. Then, the functional relationship of the current-phase relationship of the field-effect superconducting Josephson junction device 10 is expressed as: θ = arcsin (I C / I S )+2πL J I S / Ф0, where I C Expressed as the critical current, I S is represented by the superconducting current of the field effect superconducting Josephson junction device, and θ is represented by the phase θ of the superconducting wave function in the left bank electrode of the bridge junction. LThe phase θ of the wave function in the right bank electrode of the bridge junction R The phase difference, Ф0 is represented by a magnetic flux quantum, L J L is expressed as the equivalent inductance of the field effect superconducting Josephson junction device, and the longer the weak connection length of the two superconductors is (the longer the bridge length of the nanobridge 150 is), the greater the L J The bigger.

[0073] Specifically, such as Figure 8 As shown, when the voltage V gate When the voltage V gate =V g4 When the current I S The relationship with the phase θ is approximately sinusoidal. When the voltage V gate =V g1 When the current I S -phase θ relationship is approximately linear. By applying different voltages V gate , the current I S -The phase θ relationship is modulated to the required curve.

[0074] Example 2

[0075] This embodiment provides a method for preparing a field-effect superconducting Josephson junction device 10 , and the method includes steps S1) to S6).

[0076] Step S1): providing a substrate 110 and forming a first superconducting material layer on the upper surface of the substrate 110 .

[0077] In this embodiment, the material of the substrate 110 is at least one of MgO, sapphire, Si3N4, Al2O3 and SiO2, or other materials that allow the growth of superconducting thin films; the method of forming the first superconducting material layer includes but is not limited to magnetron sputtering, chemical vapor deposition, etc.

[0078] Step S2), forming a patterned mask layer on the upper surface of the first superconducting material layer, and etching the first superconducting material layer based on the mask layer, such as Figure 9 As shown, a bridge left bank electrode 120 , a bridge right bank electrode 130 and a trench 141 between the bridge left bank electrode 120 and the bridge right bank electrode 130 are formed.

[0079] In this embodiment, a coating process can be first used to form a photoresist layer on the upper surface of the first superconducting material layer, and then, the photoresist layer can be patterned by exposure and development methods. Then, the patterned photoresist layer is used as a mask to etch (such as plasma etching) the first superconducting material layer to form a groove 141. At this time, the first superconducting material layer is divided into a bridge left bank electrode 120 and a bridge right bank electrode 130 by the groove 141, and the bridge left bank electrode 120 and the bridge right bank electrode 130 are not in contact (not electrically connected).

[0080] In step S3 , the trench 141 is filled to form an insulating trench 140 that isolates the bridge left-bank electrode 120 from the bridge right-bank electrode 131 .

[0081] In this embodiment, chemical vapor deposition or other processes can first be used to deposit a layer of insulating material on the left-bank bridge electrode 120, the right-bank bridge electrode 130 and the groove 141, and then the insulating material layer can be thinned by, for example, a chemical mechanical polishing process until the upper surfaces of the left-bank bridge electrode and the right-bank bridge electrode are exposed. The thinned insulating material layer is located in the groove, and its upper surface is flush with the upper surfaces of the left-bank bridge electrode and the right-bank bridge electrode, thus forming an insulating channel sandwiched between the left-bank bridge electrode and the right-bank bridge electrode.

[0082] Step S4), such as Figure 10 As shown, a nanobridge is formed on the upper surfaces of the bridge left bank electrode, the insulating trench and the bridge right bank electrode, crossing the insulating trench to connect the bridge left bank electrode with the bridge right bank electrode.

[0083] In this embodiment, a second superconducting material layer is deposited and then patterned to prepare a nanobridge. The thickness of the second superconducting material layer is much smaller than that of the first superconducting material layer. For example, the thickness of the second superconducting material layer is within 30% of the thickness of the first superconducting material layer. The superconducting current of the Josephson junction is not only related to the critical current (density), but also to the cross-sectional area of ​​the two superconductors (the left-bank electrode of the bridge junction and the left-bank electrode of the bridge junction). The thicker left-bank electrode of the bridge junction and the left-bank electrode of the bridge junction (the first superconducting material layer) can enable the device to have a larger superconducting current flow when the critical current is limited. The thinner nanobridge (the second superconducting material layer) helps to ensure that the Josephson junction has a better nonlinear current-phase relationship.

[0084] In step S5 , an insulating dielectric layer is formed on the upper surfaces of the nanobridge, the bridge left-bank electrode, the insulating trench, and the bridge right-bank electrode.

[0085] In this embodiment, the insulating dielectric layer may be formed by a chemical vapor deposition process, and the insulating dielectric layer covers the nanobridge to isolate the nanobridge from a subsequently formed voltage electrode.

[0086] Step S6), as Figure 1 As shown, a voltage electrode 170 is formed on the upper surface of the insulating dielectric layer. Figure 2 As shown, in the top view direction, the projection of the voltage electrode at least covers the overlapping area of ​​the nanobridge and the insulating channel.

[0087] In this embodiment, a physical sputtering deposition process may be used to form a voltage electrode, which is used to apply a modulated electric field to the nanobridge to change the magnitude of the critical current and modulate the current-phase relationship.

[0088] In summary, the field-effect superconducting Josephson junction device of the present invention and the preparation method thereof isolate the left-bank electrode and the right-bank electrode of the bridge junction through an insulating trench, realize a weak connection between the left-bank electrode and the right-bank electrode of the bridge junction through a nanobridge, apply an electric field through a voltage electrode above the nanobridge to change the critical current of the junction to obtain a large critical current, and the thinner nanobridge and the thicker left-bank electrode and right-bank electrode of the bridge junction are located in different structural layers, which can enable the device to have a current-phase relationship with better nonlinearity. At the same time, the nanobridge also uses superconducting materials, which can ensure that the operating temperature of the device is equivalent to the operating temperature of the left (or right) bank superconducting electrode, so that the operating temperature is not too low.

[0089] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may 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 one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A field-effect superconducting Josephson junction device, characterized in that: The field effect superconducting Josephson junction device comprises: a substrate, a bridge junction left bank electrode, a bridge junction right bank electrode, an insulating channel, a nanobridge, an insulating dielectric layer and a voltage electrode; The bridge junction left bank electrode, the insulating trench and the bridge junction right bank electrode are located on the upper side of the substrate, and the insulating trench isolates the bridge junction left bank electrode and the bridge junction right bank electrode from each other; The nanobridge spans the insulating trench to connect the left-bank electrode of the bridge junction with the right-bank electrode of the bridge junction, and is located at least on a portion of the upper surface of the left-bank electrode of the bridge junction and a portion of the upper surface of the right-bank electrode of the bridge junction; The insulating dielectric layer covers the nanobridge and is arranged on the upper side of the bridge junction left bank electrode, the insulating channel and the bridge junction right bank electrode; The voltage electrode is located on the upper side of the insulating dielectric layer, and in a top view direction, the projection of the voltage electrode at least covers the overlapping area of ​​the nanobridge and the insulating channel.

2. The field-effect superconducting Josephson junction device according to claim 1, characterized in that: The thickness of the nanobridge is smaller than the thickness of the left-bank electrode of the bridge junction, and is also smaller than the thickness of the right-bank electrode of the bridge junction.

3. The field-effect superconducting Josephson junction device according to claim 1, characterized in that: The field effect superconducting Josephson junction device further includes an isolation layer, The isolation layer is located on the upper side of the substrate and on the lower side of the bridge junction right bank electrode, isolating the bridge junction right bank electrode from the substrate.

4. The field-effect superconducting Josephson junction device according to claim 1, characterized in that: The bridge length of the nanobridge is less than the coherence length of the superconducting material used for the nanobridge.

5. The field-effect superconducting Josephson junction device according to claim 1, characterized in that: The thickness of the nanobridge is smaller than the penetration depth of the superconducting material used in the nanobridge.

6. The field-effect superconducting Josephson junction device according to claim 1, characterized in that: The nanobridge, the bridge junction left bank electrode and the bridge junction right bank electrode adopt the same superconducting material.

7. The field-effect superconducting Josephson junction device according to claim 1, characterized in that: The material of the substrate includes at least one of MgO, sapphire, Si3N4, Al2O3 and SiO2; the material of the bridge left bank electrode includes at least one of Nb, NbN, NbTi and NbTiN; the material of the bridge right bank electrode includes at least one of Nb, NbN, NbTi and NbTiN.

8. The field-effect superconducting Josephson junction device according to any one of claims 1 to 7, characterized in that: Changing the critical current of the field-effect superconducting Josephson junction device by adjusting the voltage of the voltage electrode; By the formula θ=arcsin(I C / I S )+2πL J I S / Ф0, modulates the current-phase relationship of the field-effect superconducting Josephson junction device, where I C Expressed as the critical current, I S is represented by the superconducting current of the field effect superconducting Josephson junction device, θ is represented by the phase difference between the wave function in the left bank electrode of the bridge junction and the wave function in the right bank electrode of the bridge junction, L J It represents the equivalent inductance of the field effect superconducting Josephson junction device, and Φ0 represents a magnetic flux quantum.

9. A method for preparing a field-effect superconducting Josephson junction device, characterized in that: The preparation method comprises: S1), providing a substrate, and forming a first superconducting material layer on the upper surface of the substrate; S2), forming a patterned mask layer on the upper surface of the first superconducting material layer, and etching the first superconducting material layer based on the mask layer to form a bridge junction left bank electrode, a bridge junction right bank electrode and a trench, wherein the trench is located between the bridge junction left bank electrode and the bridge junction right bank electrode; S3), filling the trench to form an insulating trench; S4), forming a nanobridge on the upper surfaces of the bridge junction left bank electrode, the insulating trench, and the bridge junction right bank electrode, wherein the nanobridge spans the insulating trench to connect the bridge junction left bank electrode and the bridge junction right bank electrode; S5), forming an insulating dielectric layer on the upper surfaces of the nanobridge, the bridge junction left bank electrode, the insulating trench and the bridge junction right bank electrode; S6), forming a voltage electrode on the upper surface of the insulating dielectric layer, wherein, in a top view, a projection of the voltage electrode at least covers an overlapping area of ​​the nanobridge and the insulating channel.

10. The field-effect superconducting Josephson junction device according to claim 9, characterized in that: The thickness of the nanobridge is smaller than the thickness of the first superconducting material layer.

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