Light control high-frequency rectification device based on CaZrO3 / KTaO3 interface two-dimensional electron gas and preparation method

Abstract

The invention provides a light-controlled high-frequency rectification device based on CaZrO3 / KTaO3 interface two-dimensional electron gas and a preparation method thereof, and the light-controlled high-frequency rectification device comprises a KTaO3 single-crystal substrate which has the insulativity; the amorphous CaZrO3 thin film is arranged on a partial area of the surface of the KTaO3 single crystal substrate, the area is a conductive area, the area, which is not covered by the amorphous CaZrO3 thin film, of the surface of the KTaO3 single crystal substrate is an insulating area, and a CaZrO3 / KTaO3 heterojunction interface in a Hall device shape is formed; and a conductive two-dimensional electron gas is formed at the interface of the CaZrO3 / KTaO3 heterojunction. The light-controlled high-frequency rectification device realizes high-frequency electromagnetic signal rectification under the conditions of no bias voltage and no magnetic field by using a nonlinear Hall effect at a low temperature under the excitation of light.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of oxide electronics and the technical field of rectifier devices, in particular to a light-regulated high-frequency rectifier device based on a CaZrO3 / KTaO3 interface two-dimensional electron gas and a preparation method. BACKGROUND

[0002] The core feature of rectification is that there is a significant difference in the steady-state current amplitude between forward bias and reverse bias under the same amplitude of a driving signal. Traditional rectifier devices, represented by semiconductor diodes, exhibit strong unidirectional conduction characteristics based on the physical mechanism of PN junctions or Schottky barriers, and can convert alternating current signals into direct current signals. By constructing specific circuit topologies with diodes and resistors, capacitors and other components, various functions such as AC rectification and modulation signal detection (demodulation) can be achieved.

[0003] However, traditional diode rectifier devices have many limitations. Their unidirectional conduction depends on the time-reversal symmetry breaking induced by external bias or magnetic field, and in the high frequency band, the parasitic effect leads to increased energy consumption and decreased conversion efficiency. In addition, the lowest operating temperature of existing non-superconducting diodes is usually only-65 ℃, i.e. 208 K, which cannot meet the low-temperature application requirements. These defects limit the further development of traditional diodes in the fields of Internet of Things and microwave communication. It is worth noting that wireless radio frequency energy harvesting and other scenarios urgently need to break through the bottleneck of high-frequency rectification under zero bias and without magnetic field. SUMMARY

[0004] In view of the deficiencies of the prior art, the application provides a light-regulated high-frequency rectifier device based on a CaZrO3 / KTaO3 interface two-dimensional electron gas and a preparation method, which at least partially solve the above technical problems.

[0005] In one aspect, the application provides a light-regulated high-frequency rectifier device based on a CaZrO3 / KTaO3 interface two-dimensional electron gas, which comprises: a KTaO3 single crystal substrate having insulating properties; an amorphous CaZrO3 thin film arranged on a part of the surface of the KTaO3 single crystal substrate, the part being a conductive region, and the region of the surface of the KTaO3 single crystal substrate not covered by the amorphous CaZrO3 thin film being an insulating region, forming a CaZrO3 / KTaO3 heterojunction interface in the shape of a Hall device; and a conductive two-dimensional electron gas formed at the CaZrO3 / KTaO3 heterojunction interface.

[0006] Another aspect of the present application provides a preparation method for preparing the optical control high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas, which comprises: growing an amorphous CaZrO3 film on the surface of a KTaO3 single crystal substrate by a pulsed laser deposition method, wherein the KTaO3 single crystal substrate generates oxygen vacancies due to oxygen deficiency in the preparation process, and the oxygen vacancies make the tantalum ions contribute extra electrons to form a conductive two-dimensional electron gas at the CaZrO3 / KTaO3 heterojunction interface; spin coating a photoresist on the surface of the amorphous CaZrO3 film, exposing and developing the photoresist to form a patterned photoresist layer; etching the amorphous CaZrO3 film based on the patterned photoresist layer, removing the patterned photoresist layer, and obtaining the optical control high-frequency rectifier device.

[0007] The optical control high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas and the preparation method have at least the following technical effects.

[0008] The optical control high-frequency rectifier device forms a two-dimensional electron gas at the CaZrO3 / KTaO3 heterojunction interface based on the oxygen vacancies provided by the amorphous CaZrO3 film to the KTaO3 single crystal substrate and the tantalum ions contributed by the KTaO3 single crystal substrate, and realizes efficient conversion of a longitudinal alternating current signal to a double-frequency nonlinear Hall voltage by virtue of the unique transport characteristics and optical control mechanism of the interface two-dimensional electron gas, so that high-frequency electromagnetic signal rectification can be realized under a bias voltage-free and magnetic field-free condition at low temperature.

[0009] The carrier concentration and mobility of the oxide interface two-dimensional electron gas can be precisely controlled by ultraviolet / visible light band laser, and the rectification ratio can be continuously adjusted by the wavelength or power of the laser, thereby breaking through the limitation of the fixed rectification ratio of a traditional diode and providing a new control means for high-frequency signal processing.

[0010] The optical control high-frequency rectifier device can work in an ultralow temperature (10 K ~100 K) environment and is suitable for frontier fields such as superconducting quantum computing, thereby expanding the application boundary of diode rectifier devices. The rectifier device has a simple structure and stable performance.

[0011] The process parameters in the preparation process of the rectifier device are clear and controllable, and high-performance rectifier devices can be prepared by controlling the process parameters. BRIEF DESCRIPTION OF DRAWINGS

[0012] The above content and other purposes, features and advantages of the present application will be more clearly understood through the following description of the embodiments of the present application with reference to the accompanying drawings, in which:

[0013] Figure 1 A structural diagram of the optical control high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas according to the embodiment of the present application is schematically shown.

[0014] Figure 2 A flow chart of a preparation method of the light-controllable high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas according to an embodiment of the present application is schematically shown.

[0015] Figure 3 A device structure diagram corresponding to each stage of the preparation process of the light-controllable high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas according to an embodiment of the present application is schematically shown.

[0016] Figure 4 A detection mode diagram of the light-controllable high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas according to an embodiment of the present application is schematically shown.

[0017] Figure 5 A diagram of the nonlinear Hall signal of the light-controllable high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas according to an embodiment of the present application versus the applied current is schematically shown. DETAILED DESCRIPTION

[0018] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. It is to be understood, however, that the description is merely exemplary and is not intended to limit the scope of the present application. In the following detailed description of the embodiments of the present application, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present application. However, it would be apparent to those skilled in the art that the embodiments of the present application can be practiced without these specific details. In other instances, well-known structures and functions have been described in detail in order to avoid obscuring the concepts of the present application.

[0019] It has been found in the implementation of the present application that a material with intrinsic spatial inversion symmetry breaking can generate a nonlinear Hall effect, which can achieve high-frequency current rectification without a traditional PN junction structure, thereby providing a new path for developing a new rectifier device.

[0020] In view of this, embodiments of the present application provide a light-controllable high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas and a preparation method thereof. Hereinafter, specific embodiments will be described in detail,

[0021] Figure 1 A structure diagram of the light-controllable high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas according to an embodiment of the present application is schematically shown.

[0022] As Figure 1As shown, the light-controlled high-frequency rectifier device based on the two-dimensional electron gas of the CaZrO3 / KTaO3 interface in this embodiment may include a KTaO3 (KTO) single crystal substrate and an amorphous CaZrO3 (CZO) thin film disposed on the surface of the KTaO3 single crystal substrate.

[0023] KTaO3 single crystal substrates possess insulation properties and a high dielectric constant.

[0024] An amorphous CaZrO3 thin film is deposited on a portion of the surface of a KTaO3 single-crystal substrate. This portion is a conductive region, while the area of ​​the KTaO3 single-crystal substrate surface not covered by the amorphous CaZrO3 film is an insulating region. The separation of the conductive and insulating regions results in a CaZrO3 / KTaO3 heterojunction interface shaped like a Hall device. A conductive two-dimensional electron gas is formed at the CaZrO3 / KTaO3 heterojunction interface.

[0025] According to an embodiment of the present invention, the optically modulated high-frequency rectifier is composed of a CaZrO3 / KTaO3 thin film heterostructure and is used to convert a longitudinal AC signal into a second-harmonic nonlinear Hall voltage of a certain magnitude. Due to the presence of Ta atoms, the KTaO3 single-crystal substrate has strong spin-orbit coupling. During the growth of the amorphous CaZrO3 thin film, due to the bombardment of plasma plumes, the KTaO3 single-crystal substrate interface becomes oxygen-deficient in a high-temperature, low-oxygen-pressure environment, thereby generating a large number of oxygen vacancies. The appearance of oxygen vacancies causes Ta ions to contribute excess electrons, thus forming a conductive two-dimensional electron gas interface. The two-dimensional electron gas at the interface has high mobility and photoresponse characteristics, and its carrier concentration and carrier mobility can be modulated by optical modulation. The optically modulated high-frequency rectifier applies a longitudinal AC signal to the circuit using an ammeter, and measures the transverse second-harmonic nonlinear Hall voltage using a lock-in amplifier and other means to characterize the device's rectification performance.

[0026] In some embodiments, the thickness of the amorphous CaZrO3 thin film ranges from 8 nm to 20 nm.

[0027] In some embodiments, the operating temperature of the optically controlled high-frequency rectifier is 10 K ~ 100 K.

[0028] It should be noted that the thickness of the KTaO3 single crystal substrate and the type of photoresist have little impact on the performance of light-controlled high-frequency rectifier devices.

[0029] Figure 2 The flowchart illustrating the fabrication method of a light-controlled high-frequency rectifier device based on a two-dimensional electron gas at the CaZrO3 / KTaO3 interface according to an embodiment of the present invention is shown.

[0030] like Figure 2 As shown, the preparation method may include operations S210 to S230.

[0031] In operation S210, an amorphous CaZrO3 film is grown on a surface of a KTaO3 single crystal substrate by a pulsed laser deposition method to form a CaZrO3 / KTaO3 heterojunction. The KTaO3 single crystal substrate generates oxygen vacancies due to oxygen deficiency in a preparation process. The oxygen vacancies cause the tantalum ions to contribute excess electrons, and thus a conductive two-dimensional electron gas is formed at an interface of the CaZrO3 / KTaO3 heterojunction.

[0032] In operation S220, a photoresist is spin-coated on the surface of the amorphous CaZrO3 film, and the photoresist is exposed and developed to form a patterned photoresist layer.

[0033] In operation S230, the amorphous CaZrO3 film is etched based on the patterned photoresist layer, and the patterned photoresist layer is removed to obtain a light-controlled high-frequency rectifier device.

[0034] In some embodiments, the target material for growing the amorphous CaZrO3 film can be a polycrystalline target material, and the purity of the polycrystalline target material is greater than or equal to 99.99%.

[0035] In some embodiments, the pulsed laser deposition method for growing the amorphous CaZrO3 film on the surface of the KTaO3 single crystal substrate can include:

[0036] The process parameters for growing the amorphous CaZrO3 film include a growth temperature of a fixed value between 600 ℃ and 700 ℃, an oxygen pressure of a fixed value between 2×10 -6 mbar and 5×10 -5 mbar, a laser wavelength of 248 nm, a laser energy density of 2 J / cm 2 , a pulse frequency of 2 Hz, a deposition time of 8 min to 20 min, and a growth rate of 1 nm / min.

[0037] In some embodiments, the photoresist is spin-coated on the surface of the amorphous CaZrO3 film, and the process parameters include a spin-coating rotation speed of 5000 r / min and a spin-coating time of 30 s to 40 s, and a pre-baking temperature of 100 ℃ and a pre-baking time of 2 min.

[0038] In some embodiments, the photoresist is exposed and developed, and the process parameters include:

[0039] In some embodiments, the photoresist is exposed and developed, and the process parameters include:

[0040] The photoresist is exposed and developed with process parameters of an exposure wavelength of 365 nm, an exposure time of 18 s, a developing time of 35 s, an etching time of 2 min to 3 min, an RF power of 200 W, and an etching power of 500 W. The etching method can be inductively coupled plasma etching.

[0041] In some embodiments, etching the amorphous CaZrO3 film based on the patterned photoresist layer can include:

[0042] The amorphous CaZrO3 film is etched with process parameters of an etching time of 2 min.

[0043] In some embodiments, the preparation method can further include:

[0044] Before growing the amorphous CaZrO3 film on the surface of the KTaO3 single crystal substrate by the pulsed laser deposition method, the KTaO3 single crystal substrate is sequentially ultrasonically cleaned in acetone, ethanol, and deionized water, and dried by introducing nitrogen gas.

[0045] To more clearly illustrate the light modulated high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas and the preparation method provided by the embodiments of the present application, a specific example is listed below for illustration.

[0046] Figure 3 The device structure diagrams corresponding to each stage of the preparation process of the light modulated high-frequency rectifier device based on the CaZrO3 / KTaO3 interface two-dimensional electron gas according to the embodiments of the present application are schematically shown.

[0047] As shown in Figure 3 , a KTaO3 single crystal substrate with <111> crystal phase is selected, and the substrate size is 5mm*5mm*0.5mm. The substrate is sequentially ultrasonically cleaned in acetone, ethanol, and deionized water, and dried by introducing nitrogen gas. A CaZrO3 film is grown on the substrate by using the pulsed laser deposition technology, the growth temperature is 600 ℃, the oxygen pressure is 5×10 -5 mbar, the laser wavelength is 248nm, and the laser energy density is 2 J / cm 2, the pulse frequency is 2 Hz, the deposition time is 10 min, and the growth rate is 1 nm / min. The thickness of the CaZrO3 film is about 10 nm, and the thickness of the film basically does not affect the performance of the device. Due to the bombardment of the plasma plume in the pulsed laser deposition process, the interface of the KTaO3 single crystal substrate will become oxygen-deficient in a high-temperature and low-oxygen-pressure environment, and a large number of oxygen vacancies will be formed, thereby forming a conductive two-dimensional electron gas at the CaZrO3 / KTaO3 interface. A drop of S1818 photoresist is added to the KTaO3 on which the CaZrO3 film is grown, and a spin coater is used to spin at a speed of 5000 r / min for 30 s, thereby forming a photoresist film with a thickness of 1.3 μm on the surface of the thin film device. Then it is placed on a hot plate for baking, the baking temperature is 100 ℃, and the baking time is 2 min. Then the mask exposure is performed using the SUSS MA6 ultraviolet photolithography machine, the exposure wavelength is 365 nm, and the exposure time is 18 s. The exposed thin film device is immediately placed in the developing solution, and the developing time is 35 s. Finally, the ICP inductively coupled plasma etching machine is used for argon etching, the etching time is 2 min, the radio frequency power is 200 W, and the ICP power is 500 W.

[0048] Figure 4 A schematic diagram of a detection mode of a light-regulated high-frequency rectifier device based on a CaZrO3 / KTaO3 interface two-dimensional electron gas according to an embodiment of the application is shown.

[0049] As shown in Figure 4 , a wire bonder is used to bond aluminum wires between the six electrodes of the device and the sample holder conductive electrodes. An AC signal with a frequency of 17.777 Hz is applied in the x direction using a current source, and a tunable laser is used to vertically irradiate the device channel region. The longitudinal fundamental frequency voltage and the transverse second harmonic Hall voltage are synchronously collected by a double lock-in amplifier. Two lock-in amplifiers are used to measure the longitudinal and transverse AC signals, respectively, and the second harmonic transverse voltage is extracted. Different frequency light is vertically irradiated on the surface of the device.

[0050] The device performance is verified at a low temperature of 10 K by a comprehensive physical property measurement system. In a zero magnetic field, a reference AC current with a frequency of 17.777 Hz is applied in the longitudinal direction of the device, and a 405 nm laser is used to irradiate the surface of the device. The transverse nonlinear Hall voltage is detected in real time.

[0051] Figure 5 A graph showing the relationship between the nonlinear Hall signal of a light-regulated high-frequency rectifier device based on a CaZrO3 / KTaO3 interface two-dimensional electron gas and the applied current according to an embodiment of the application is shown.

[0052] As shown in Figure 5As shown, when the light intensity is less than or equal to 0.05 mW, the second harmonic transverse voltage and the applied alternating current present a square relationship; when the light intensity exceeds 0.05 mW, the second harmonic transverse voltage still maintains the quadratic function characteristic but the amplitude decays. The basic characteristics of the device satisfy the formula The frequency doubling detection can be realized.

[0053] The above describes the embodiments of the present application. However, these embodiments are only for illustrative purposes, and are not intended to limit the scope of the present application. Although each embodiment is described above respectively, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present application is defined by the appended claims and their equivalents. Without departing from the scope of the present application, those skilled in the art can make various substitutions and modifications, which should all fall within the scope of the present application.

Claims

1. A light-controlled high-frequency rectifier device based on a two-dimensional electron gas at the CaZrO3 / KTaO3 interface, characterized in that, include: KTaO3 single crystal substrate, which has insulating properties; An amorphous CaZrO3 thin film is disposed on a portion of the surface of the KTaO3 single crystal substrate. This portion is a conductive region, and the area of ​​the KTaO3 single crystal substrate surface not covered by the amorphous CaZrO3 thin film is an insulating region, forming a CaZrO3 / KTaO3 heterojunction interface in the shape of a Hall device. A conductive two-dimensional electron gas is formed at the CaZrO3 / KTaO3 heterojunction interface.

2. The optically modulated high-frequency rectifier device according to claim 1, characterized in that, The thickness of the amorphous CaZrO3 thin film ranges from 8 nm to 20 nm.

3. The optically modulated high-frequency rectifier device according to claim 1 or 2, characterized in that, The operating temperature of the optically controlled high-frequency rectifier is 10 K ~ 100 K.

4. A preparation method, characterized in that, The method for preparing the optically modulated high-frequency rectifier device based on a two-dimensional electron gas at a CaZrO3 / KTaO3 interface as described in any one of claims 1 to 3 includes: An amorphous CaZrO3 thin film was grown on the surface of a KTaO3 single crystal substrate using pulsed laser deposition to form a CaZrO3 / KTaO3 heterojunction. During the preparation of the KTaO3 single crystal substrate, oxygen vacancies were generated due to oxygen deficiency. These oxygen vacancies caused tantalum ions to contribute excess electrons, forming a conductive two-dimensional electron gas at the interface of the CaZrO3 / KTaO3 heterojunction. Photoresist is spin-coated onto the surface of the amorphous CaZrO3 thin film, and the photoresist is exposed and developed to form a patterned photoresist layer. The amorphous CaZrO3 thin film is etched based on the patterned photoresist layer to remove the patterned photoresist layer, thereby obtaining a light-controlled high-frequency rectifier device.

5. The preparation method according to claim 4, characterized in that, The target material for growing the amorphous CaZrO3 thin film is a polycrystalline target material, and the purity of the polycrystalline target material is greater than or equal to 99.99%.

6. The preparation method according to claim 4 or 5, characterized in that, The method of growing amorphous CaZrO3 thin films on KTaO3 single-crystal substrates using pulsed laser deposition includes: With a growth temperature of 600 ℃ ~ 700 ℃ and an oxygen pressure of 2 × 10 -6 mbar ~5×10 -5 Given a fixed value between mbar and 248 nm laser wavelength, and a laser energy density of 2 J / cm², 2 The amorphous CaZrO3 thin film was grown using process parameters of 2 Hz pulse frequency, 8 min ~ 20 min deposition time, and 1 nm / min growth rate.

7. The preparation method according to claim 4, characterized in that, The process of spin-coating photoresist onto the amorphous CaZrO3 thin film includes: The photoresist was spin-coated using process parameters of 5000 r / min spin-coating speed, 30 s ~ 40 s spin-coating time, 100 ℃ pre-baking temperature, and 2 min pre-baking time.

8. The preparation method according to claim 4, characterized in that, The exposure and development of the photoresist includes: The photoresist was exposed and developed using process parameters of 365 nm exposure wavelength, 18 s exposure time, 35 s development time, and 2 min etching time.

9. The preparation method according to claim 4, characterized in that, The etching of the amorphous CaZrO3 thin film based on the patterned photoresist layer includes: The amorphous CaZrO3 thin film was etched using process parameters of 2 min to 3 min etching time, 200 W radio frequency power, and 500 W etching power.

10. The preparation method according to claim 4, characterized in that, The preparation method further includes: Before growing an amorphous CaZrO3 thin film on the surface of a KTaO3 single crystal substrate using pulsed laser deposition, the KTaO3 single crystal substrate was ultrasonically cleaned in acetone, ethanol and deionized water in sequence, and nitrogen gas was introduced to dry the surface of the KTaO3 single crystal substrate.

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