Surface acoustic wave device and method for measuring carrier drift speed thereof

Abstract

The invention relates to the technical field of semiconductors, and provides a surface acoustic wave device and a method for measuring the carrier drift speed thereof. The method comprises the following steps: applying an alternating current voltage and direct current bias voltages with different magnitudes to the measurer, and measuring second insertion loss of the measurer under different direct current bias voltages; calculating a difference value between the second insertion loss and the first insertion loss under different direct-current bias voltages to obtain insertion loss change values under different direct-current bias voltages, and obtaining a corresponding relation between the insertion loss change values and the direct-current bias voltages; based on the corresponding relation between the insertion loss change value and the direct current bias voltage, obtaining the corresponding relation between the attenuation / gain coefficient and the direct current bias voltage; based on the corresponding relation between the attenuation / gain coefficient and the direct current bias voltage, the corresponding relation between the carrier drift speed and the direct current bias voltage is obtained, and measurement of the carrier drift speed is completed. And drift velocity continuous measurement of full electric field coverage can be realized.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a surface acoustic wave device and a method for measuring carrier drift velocity thereof. Background Art

[0002] The performance of semiconductor materials determines the functionality and efficiency of a wide range of devices, from consumer electronics to industrial systems. The application of semiconductor devices has expanded from traditional integrated circuits to cutting-edge fields such as 5G communications, artificial intelligence, new energy, and the Internet of Things, placing higher demands on the electronic transport properties of materials. The core performance of semiconductor materials depends on the transport behavior of charge carriers (electrons or holes), and the carrier drift velocity is a key parameter in studying this behavior. Measuring the carrier drift velocity is crucial for revealing the microscopic mechanisms of charge transport in materials and providing experimental validation for theoretical models.

[0003] Currently, mainstream carrier drift velocity characterization techniques fall into two categories: electrical (time-of-flight method, Hall effect method) and optical (terahertz time-domain spectroscopy, pump-probe technique). However, these techniques are either limited in measurement range (e.g., covering only low or high fields) or constrained by sample type and experimental conditions. Consequently, they are unable to universally measure the carrier drift velocity-electric field relationship across the entire electric field range.

[0004] Therefore, exploring a universal carrier drift velocity-electric field relationship measurement technology with a large dynamic electric field range is an urgent problem that those skilled in the art need to solve. Summary of the Invention

[0005] In view of this, an embodiment of the present application provides a surface acoustic wave device and a method for measuring carrier drift velocity thereof, which can realize carrier drift velocity measurement within the entire electric field range.

[0006] A first aspect of an embodiment of the present application provides a surface acoustic wave device, comprising: a supporting substrate; a dielectric layer, located on the upper surface of the supporting substrate; a piezoelectric layer, located on the upper surface of the dielectric layer; interdigitated electrodes, discretely disposed on both sides of the upper surface of the piezoelectric layer; a semiconductor thin film layer, located on the upper surface of the piezoelectric layer and disposed between the interdigital electrodes on both sides; The ohmic electrode is located on the upper surface of the piezoelectric layer and is arranged on both sides of the semiconductor film in ohmic contact.

[0007] In one embodiment, the material of the support substrate includes at least one of silicon, silicon oxide, silicon carbide, sapphire, diamond, quartz, aluminum nitride, gallium nitride, gallium oxide, and zinc oxide; The material of the dielectric layer is one of silicon dioxide, silicon nitride, aluminum oxide, aluminum oxide, and silicon carbide; The material of the piezoelectric layer is one of lithium niobate, potassium niobate, lithium tantalate, aluminum nitride, quartz, zinc oxide, and gallium oxide; The interdigital electrodes and the ohmic electrodes include a single layer or multiple layers of metal, and the metal material of the interdigital electrodes and the ohmic electrodes is one of gold, silver, copper, platinum, aluminum, molybdenum, titanium, and nickel.

[0008] In one embodiment, the ratio of the thickness of the piezoelectric layer to the wavelength of the excited target elastic wave is less than 1 and greater than 0.1.

[0009] In one embodiment, the fingers of the interdigitated electrodes are parallel to each other, and an angle between a vertical direction of the fingers and a propagation direction of a target elastic wave is less than 40°.

[0010] A second aspect of the embodiments of the present application provides a method for measuring carrier drift velocity using the surface acoustic wave device provided by the first aspect of the embodiments of the present application, comprising: applying an AC voltage to the measuring device to measure a first insertion loss of the measuring device without a bias voltage; applying an AC voltage and DC bias voltages of different magnitudes to the measuring device, and measuring a second insertion loss of the measuring device under the different DC bias voltages; Calculating the difference between the second insertion loss and the first insertion loss under different DC bias voltages to obtain insertion loss change values ​​under different DC bias voltages, and obtaining a corresponding relationship between the insertion loss change value and the DC bias voltage; Based on the corresponding relationship between the insertion loss change value and the DC bias voltage, obtaining the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage; Based on the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage, the corresponding relationship between the carrier drift velocity and the DC bias voltage is obtained, and the carrier drift velocity measurement is completed.

[0011] In one embodiment, applying an AC voltage and DC bias voltages of different magnitudes to the measuring device and measuring the second insertion loss of the measuring device under the different DC bias voltages includes: applying an AC voltage of a specified magnitude to the measuring device; Within a specified voltage range, DC bias voltages of different magnitudes are selected at equal intervals and applied to the measuring device in sequence, and the second insertion loss of the measuring device under different DC bias voltages is measured.

[0012] In one embodiment, obtaining the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage based on the corresponding relationship between the insertion loss change value and the DC bias voltage includes: Based on the formula , deriving a corresponding relationship between the attenuation / gain coefficient and the DC bias voltage from the corresponding relationship between the insertion loss change value and the DC bias voltage; in, IL is the insertion loss change value, and α is the attenuation / gain coefficient.

[0013] In one embodiment, obtaining the corresponding relationship between the carrier drift velocity and the DC bias voltage based on the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage includes: Based on the formula , deriving the corresponding relationship between the carrier drift velocity and the DC bias voltage from the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage; Among them, K 2 is the intrinsic electromechanical coupling coefficient, ω c is the dielectric relaxation frequency, ω D is the diffusion frequency, α is the attenuation / gain coefficient, is the diffusion length, is the wave vector, γ is a variable used to reflect the relationship between the carrier drift velocity and the speed of sound.

[0014] In one embodiment, the attenuation / gain coefficient α Calculated using the following formula: ; k = ω / v s ; ω c = σ / ε; ω D = v s 2 / D n ; γ = 1 - v dri / v s ; K 2 = e 2 / εc; in, γ is a variable used to reflect the relationship between the carrier drift velocity and the speed of sound, v s is the propagation velocity of sound waves, v dri is the carrier drift velocity, σ is the conductivity, ε is the dielectric constant, D n is the electron diffusion coefficient, ω is the angular frequency, and c is the speed of light.

[0015] In one embodiment, based on the correspondence between the attenuation / gain coefficient and the DC bias voltage, the correspondence between the carrier drift velocity and the DC bias voltage is obtained, and before the carrier drift velocity measurement is completed, the method further comprises: applying a DC bias voltage to the measurer, measuring the current-voltage characteristic of the measurer, and extracting the conductivity σ.

[0016] The second aspect of the embodiments of the present application provides a measurement method, which comprises the following steps: applying an AC voltage to a measurer, measuring a first insertion loss of the measurer under no bias voltage; applying an AC voltage and different magnitudes of DC bias voltage to the measurer, measuring second insertion losses of the measurer under different DC bias voltages; calculating the difference between the second insertion losses under different DC bias voltages and the first insertion loss, obtaining an insertion loss change value under different DC bias voltages, and obtaining the correspondence between the insertion loss change value and the DC bias voltage; based on the correspondence between the insertion loss change value and the DC bias voltage, obtaining the correspondence between the attenuation / gain coefficient and the DC bias voltage; and based on the correspondence between the attenuation / gain coefficient and the DC bias voltage, obtaining the correspondence between the carrier drift velocity and the DC bias voltage, and completing the carrier drift velocity measurement. By using the electro-acoustic interaction, the semiconductor carrier drift velocity measurement under any bias voltage (i.e. in the full electric field range) can be realized by adjusting the magnitude of the applied bias voltage. By comparing the insertion loss change of the no-bias reference state and the bias state, the system error of the device itself insertion loss is eliminated. The insertion loss change value directly maps the sound wave attenuation / gain strength, and then realizes the continuous measurement of the drift velocity in the full electric field coverage, breaking through the limitation of the traditional method of segmented measurement in the low field or high field. The measurement method has low calculation complexity, does not need temperature variation operation, and the preparation process is compatible with the traditional CMOS process, which is conducive to large-scale use.

[0017] It can be understood that the beneficial effects of the first aspect described above can be referred to the related description in the second aspect described above, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating any inventive labor.

[0019] Figure 1 is a structural schematic diagram of a surface acoustic wave device provided by an embodiment of the present application; Figure 2 is a radio frequency S parameter curve diagram of a semiconductor thin film under no bias voltage provided by another embodiment of the present application; Figure 3 This is a flow chart of a method for measuring carrier drift velocity based on surface acoustic waves provided in another embodiment of the present application; Figure 4 is an attenuation / gain-bias voltage curve diagram provided in an embodiment of the present application; Figure 5 This is a drift speed-voltage curve diagram provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0021] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0022] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0023] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0024] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0025] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0026] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0027] like Figure 1 As shown, a first aspect of an embodiment of the present application provides a surface acoustic wave device, comprising: Support substrate 100; The dielectric layer 200 is located on the upper surface of the supporting substrate 100; The piezoelectric layer 300 is located on the upper surface of the dielectric layer 200; Interdigital electrodes 400 are discretely disposed on both sides of the upper surface of the piezoelectric layer 300; The semiconductor thin film layer 500 is located on the upper surface of the piezoelectric layer 300 and is disposed between the interdigital electrodes 400 on both sides; The ohmic electrode 600 is located on the upper surface of the piezoelectric layer 300 and is provided on both sides of the semiconductor film in ohmic contact.

[0028] In application, the surface acoustic wave-based carrier drift velocity meter provided in this application is used to measure the drift velocity of carriers in various semiconductor materials under bias voltage, providing a reliable experimental reference for the design of electrical devices.

[0029] The discrete, two-sided layout of interdigitated electrodes in this embodiment precisely defines the surface acoustic wave excitation region. The semiconductor film is positioned at the core of the acoustic wave propagation path, and ohmic electrodes directly contact both sides of the film to form a carrier acceleration channel. This design optimizes the efficiency of electroacoustic energy coupling. The spatial alignment of the surface acoustic wave propagation path with the direction of carrier motion significantly enhances the interaction strength, providing a physical basis for sensitive drift velocity detection.

[0030] In one embodiment, the material of the support substrate 100 is one of silicon, silicon oxide, silicon carbide, sapphire, diamond, quartz, aluminum nitride, gallium nitride, gallium oxide, and zinc oxide; The material of the dielectric layer 200 is one of silicon dioxide, silicon nitride, aluminum oxide, aluminum oxide, and silicon carbide; The material of the piezoelectric layer 300 is one of lithium niobate, potassium niobate, lithium tantalate, aluminum nitride, quartz, zinc oxide, and gallium oxide; The interdigital electrodes 400 and the ohmic electrodes 600 include a single layer or multiple layers of metal. The metal material of the interdigital electrodes 400 and the ohmic electrodes 600 is one of gold, silver, copper, platinum, aluminum, molybdenum, titanium, and nickel.

[0031] In one embodiment, the ratio of the thickness of the piezoelectric layer 300 to the wavelength of the excited target elastic wave is less than 1 and greater than 0.1.

[0032] In one embodiment, the fingers of the interdigitated electrode 400 are parallel to each other, and the angle between the vertical direction of the fingers and the propagation direction of the target elastic wave is less than 40°.

[0033] In applications, the semiconductor thin film layer can be made of any semiconductor material. The interdigitated electrodes and ohmic electrodes are composed of a single or multiple metal layers, and the metal compositions of the two can be the same or different. The ohmic electrodes are connected to the semiconductor thin film structure to form an ohmic contact. The number of interdigitated electrodes is greater than two, and the thickness of the dielectric layer is greater than or equal to zero. Specifically, the thickness of the dielectric layer can be 0-2 μm, the thickness of the semiconductor thin film can be 20 nm-1000 nm, and the length of the semiconductor thin film can be 10 μm-1000 μm.

[0034] The propagation speed of the acoustic wave in the supporting substrate 100 is greater than that in the piezoelectric layer 300. During the propagation of the excited surface acoustic wave, most of the energy is concentrated in the piezoelectric layer 300; some energy is concentrated in the composite film formed by the upper surface of the supporting substrate 100, the dielectric layer 200, and the lower surface of the piezoelectric layer 300; and a very small amount of energy leaks into the supporting substrate 100. At this time, because the equivalent wave velocity in the composite film is greater than that in the piezoelectric layer, the wave velocity of the excited acoustic wave is effectively increased. Furthermore, the introduction of the dielectric layer can effectively improve the device's temperature stability and the parasitic capacitance effect in RF operating environments.

[0035] The present invention also provides a method for preparing a surface acoustic wave-based carrier drift velocity measuring device, the method comprising: Step 101: Provide a high-wave-speed support substrate 100 .

[0036] In the application, 4H-SiC substrates with (001) crystal orientation are cleaned.

[0037] Step 102: forming a dielectric layer 200 on the upper surface of the high-wave-speed substrate.

[0038] In the application, the silicon dioxide / lithium niobate structure is transferred to the substrate through ion cutting heterogeneous integration technology.

[0039] Step 103: forming a piezoelectric layer 300 on the upper surface of the dielectric layer.

[0040] Step 104: forming a semiconductor thin film layer 500, interdigital electrodes 400 and an ohmic electrode 600 on the upper surface of the piezoelectric layer.

[0041] In practice, a semiconductor film pattern is formed on lithium niobate through resist coating, photolithography, and development. A gallium oxide film is then deposited using chemical organic vapor phase epitaxy (MOCVD). A periodic pattern of interdigitated electrodes is formed on both sides of the semiconductor film through resist coating, photolithography, and development. Metal Al is then deposited using electron beam evaporation. Ohmic electrodes are then patterned on both sides of the semiconductor film through resist coating, photolithography, and development. Ion implantation and high-temperature activation create a highly doped layer. The resist coating, photolithography, and development process is repeated to form ohmic electrode patterns on both sides of the semiconductor film. Metal Ti / Au is then deposited using electron beam evaporation, and the ohmic contact is strengthened through rapid annealing.

[0042] In applications, the dielectric layer 200, the piezoelectric layer 300 and the semiconductor thin film layer 500 can be prepared using HVPE, MOCVD, Mis-CVD, wafer bonding and other technologies; the interdigitated electrodes and the ohmic electrodes can be prepared on the piezoelectric layer using photolithography, development, electron beam evaporation, stripping or electron beam evaporation, photolithography, development, etching and other technologies; the ohmic contact between the ohmic electrode and the semiconductor thin film layer can be strengthened using rapid thermal annealing technology.

[0043] In the embodiment of the present application, a piezoelectric layer is formed on a high acoustic velocity substrate to enhance the energy confinement effect of the piezoelectric layer, thereby effectively improving the center frequency and effective electromechanical coupling coefficient of the device.

[0044] In one embodiment, this fabrication method can produce a measuring device with the following structure: the support substrate 100 is made of silicon carbide with a thickness greater than 300 μm; the dielectric layer 200 is made of silicon dioxide with a thickness t1 of 20-75 nm; the piezoelectric layer 300 is made of lithium niobate with a thickness t2 of 200-400 nm; the semiconductor thin film layer is made of gallium oxide with a thickness t of 150-300 nm and a length L2 in the direction of acoustic wave propagation of 20-30 μm. The interdigital electrodes are made of aluminum with a thickness of 80 nm; the ohmic electrodes are made of Ti / Au with a thickness of 20 nm / 80 nm and a width b of 10 μm in the direction of acoustic wave propagation. The interdigital electrode period λ (the wavelength of the acoustic wave) is 4 μm, the center-to-center distance p between adjacent interdigital electrodes is 2 μm, and the interdigital electrode width a is 1 μm. The distance L1 from the edge of the interdigital electrode period to the ohmic electrode is 10 μm; and the number of pairs of interdigital electrodes at both ends is 10.

[0045] In order to quickly illustrate the effect of this embodiment, the RF S parameters of the device of this embodiment are simulated using finite element simulation, as shown in FIG. Figure 2As shown, the center frequency of the device is about 1.5GHz, the minimum insertion loss is 5.2dB, and the maximum reflection loss is 10dB, indicating that the device has good performance and fully meets the measurement requirements.

[0046] In actual experiments, a device to be tested was prepared based on the carrier drift velocity measurement structure and preparation steps described above, and then the carrier drift velocity was measured using a vector network analyzer and a source meter. The measurement mechanism of the surface acoustic wave-based carrier drift velocity meter in the embodiment of the present application is: Applying an excitation electric field to one end of the interdigitated electrodes excites surface acoustic waves (SAWs) in the structure due to the piezoelectric effect. The phase of the SAW is a time-dependent and position-dependent quantity. The real part of the SAW wave vector k is related to the speed of sound, while the imaginary part is related to the SAW attenuation. Simultaneously, the propagation of these SAWs is accompanied by potential fluctuations. If a semiconductor film lies in the SAW propagation path, these potential fluctuations interact with the free carriers in the semiconductor, generating an electro-acoustic interaction. This electro-acoustic interaction disrupts the thermal equilibrium in the semiconductor film, causing carrier redistribution. Similarly, this carrier redistribution modulates the propagating SAWs, allowing the carrier state to be extracted from the SAWs. The greater the difference between the carrier motion in the semiconductor and the SAW, the stronger this modulation feedback effect. Applying a bias voltage across the semiconductor film along the direction of the acoustic wave propagation accelerates the free carriers in either the same or opposite directions, dramatically changing their motion. This electro-acoustic interaction then transmits the free carrier velocity state back to the SAW. The final effect is: the surface acoustic wave is amplified / attenuated, which is manifested as a change in the insertion loss of the device; the phase of the surface acoustic wave is modulated, which is manifested as a shift in the center frequency of the device. The above physical process can be quantitatively derived using the piezoelectric constitutive equation and the current continuity equation, and the attenuation / gain coefficient can be finally solved. α for: where k = ω / v s 、ω c = σ / ε, ω D = v s 2 / D n ,γ = μE0 / v s - 1. K 2 = e 2 / εc, and because w 2 / w c w D =k 2 L D 2 , so equation (1.1) can be written as: where k = ω / v s 、ω c = σ / ε, ω D = vs 2 / D n ,γ = 1 - v dri / vs, K 2 = e 2 / εc,v s is the propagation velocity of the sound wave, v dri is the carrier drift velocity, ω c is the dielectric relaxation frequency, ω D is the diffusion frequency, K 2 is the intrinsic electromechanical coupling coefficient, μ is the electron mobility, D n is the electron diffusion coefficient, and ε is the dielectric constant. From formula (1.2), we can see that the positive or negative value of α is determined only by γ. When γ is greater than 0, that is, the carrier drift velocity is greater than the sound wave propagation velocity, α is also greater than 0, and the sound wave is amplified; conversely, when γ is less than 0, that is, the carrier drift velocity is less than the sound wave propagation velocity, α is also less than 0, and the sound wave is attenuated. In formula (1.1), k, ω c 、ω D , K 2 is a parameter related only to material properties and device structure, and is a determinable constant. Only γ is a variable, so the attenuation / gain coefficient is a function related only to the carrier drift velocity. γ Solving the equation yields: The value of the carrier drift velocity can be easily obtained from γ. Therefore, in actual operation, the attenuation / gain coefficient can be measured to determine the change with the bias voltage at both ends of the semiconductor film. The carrier drift velocity can be calculated using formula (1.3). Finally, a set of curves of the carrier drift velocity changing with the DC bias voltage can be obtained, thus achieving full-range measurement of the carrier drift velocity.

[0047] like Figure 3 As shown, the embodiment of the present application further provides a method for measuring carrier drift velocity using the surface acoustic wave device of any of the above embodiments, comprising: Step 1: Apply an AC voltage to the measuring instrument and measure the first insertion loss of the measuring instrument without bias voltage.

[0048] During application, the vector network analyzer is calibrated to ensure reliable measurement results. The analyzer is then placed on a probe station. An AC signal is applied to one port of the analyzer, with the other port serving as the signal output. The calibrated vector network analyzer is then used to measure the analyzer's first insertion loss without bias voltage.

[0049] Step 2: Apply an AC voltage and DC bias voltages of different magnitudes to the measuring device, and measure the second insertion loss of the measuring device under different DC bias voltages.

[0050] In application, a DC probe is inserted into the ohmic electrodes at both ends of a prefabricated semiconductor to provide a DC bias voltage. This DC bias voltage is selected at equal intervals within a specified voltage range. This specified voltage range can be adjusted to meet measurement requirements, enabling full electric field range measurements.

[0051] Step 3: Calculate the difference between the second insertion loss and the first insertion loss under different DC bias voltages, obtain the insertion loss change value under different DC bias voltages, and obtain the corresponding relationship between the insertion loss change value and the DC bias voltage.

[0052] In applications, the insertion loss change is the difference between the second insertion loss and the first insertion loss at different DC bias voltages. By measuring multiple second insertion losses at different DC bias voltages, multiple insertion loss change values ​​can be calculated, ultimately yielding a correlation between the insertion loss change and DC bias voltage.

[0053] Step 4: Based on the corresponding relationship between the insertion loss change value and the DC bias voltage, the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage is obtained.

[0054] Step 5: Based on the correspondence between the attenuation / gain coefficient and the DC bias voltage, the correspondence between the carrier drift velocity and the DC bias voltage is obtained, and the carrier drift velocity measurement is completed.

[0055] In one embodiment, applying an AC voltage and DC bias voltages of different magnitudes to a measuring device, and measuring a second insertion loss of the measuring device under the different DC bias voltages, includes: Apply an AC voltage of a specified magnitude to the measuring device; Within a specified voltage range, DC bias voltages of different magnitudes are selected at equal intervals and applied to the measuring device in sequence, and the second insertion loss of the measuring device under different DC bias voltages is measured.

[0056] In one embodiment, based on the corresponding relationship between the insertion loss change value and the DC bias voltage, the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage is obtained, including: Based on the formula , the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage is derived from the corresponding relationship between the insertion loss change value and the DC bias voltage; in, IL is the insertion loss change value, and α is the attenuation / gain coefficient.

[0057] In one embodiment, based on the correspondence between the attenuation / gain coefficient and the DC bias voltage, the correspondence between the carrier drift velocity and the DC bias voltage is obtained, including: Based on the formula , the corresponding relationship between carrier drift velocity and DC bias voltage is derived from the corresponding relationship between attenuation / gain coefficient and DC bias voltage; Among them, K 2 is the intrinsic electromechanical coupling coefficient, ω c is the dielectric relaxation frequency, ω D is the diffusion frequency, α is the attenuation / gain coefficient, is the diffusion length, is the wave vector, γ is a variable used to reflect the relationship between the carrier drift velocity and the speed of sound.

[0058] In one embodiment, the attenuation / gain coefficient α Calculated using the following formula: ; k = ω / v s ; ω c = σ / ε; ω D = v s 2 / D n ; γ = 1 - v dri / v s ; K 2 = e 2 / εc; in, γ is a variable used to reflect the relationship between the carrier drift velocity and the speed of sound, v s is the propagation velocity of sound waves, v dri is the carrier drift velocity, σ is the conductivity, ε is the dielectric constant, D n is the electron diffusion coefficient, ω is the angular frequency, and c is the speed of light.

[0059] In one embodiment, based on the correspondence between the attenuation / gain coefficient and the DC bias voltage, the correspondence between the carrier drift velocity and the DC bias voltage is obtained. Before completing the carrier drift velocity measurement, the method further includes: A DC bias voltage is applied to the measuring device, and the current-voltage characteristics of the measuring device are measured to extract the conductivity σ.

[0060] In one embodiment, numerical calculations are used to demonstrate the carrier drift velocity measurement process, such as Figure 4 The figure shows the attenuation / gain coefficient of the electro-acoustic interaction. The black solid line in the figure is the result of assuming that the voltage and the carrier drift velocity are linearly related, and the black dotted line is the result of introducing nonlinear effects. It can be found that the existence of nonlinear effects on the high-voltage side will cause the attenuation / gain to decrease. Figure 5 Shown is based on Figure 4 The attenuation / gain coefficient in the carrier drift velocity-voltage relationship curve is calculated using formula (1.3). From the black solid line in the figure, it can be seen that the carrier drift velocity-voltage is a perfect linear relationship, which is consistent with the hypothesis; the black dotted line is the calculation result with the introduction of nonlinear effects, which is also consistent with the hypothesis.

[0061] In summary, the entire measurement process is not restricted by factors such as voltage range, material type, and whether the relationship between carrier drift velocity and voltage is linear. Therefore, universal measurement of the full range of carrier drift velocity-electric field relationship for any material can be achieved, effectively solving the current technical barriers in the field of carrier measurement.

[0062] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A surface acoustic wave device, characterized in that: include: a supporting substrate; a dielectric layer, located on the upper surface of the supporting substrate; a piezoelectric layer, located on the upper surface of the dielectric layer; interdigitated electrodes, discretely disposed on both sides of the upper surface of the piezoelectric layer; a semiconductor thin film layer, located on the upper surface of the piezoelectric layer and disposed between the interdigital electrodes on both sides; The ohmic electrode is located on the upper surface of the piezoelectric layer and is arranged on both sides of the semiconductor film in ohmic contact.

2. The surface acoustic wave device according to claim 1, wherein The material of the support substrate includes at least one of silicon, silicon oxide, silicon carbide, sapphire, diamond, quartz, aluminum nitride, gallium nitride, gallium oxide, and zinc oxide; The material of the dielectric layer is one of silicon dioxide, silicon nitride, aluminum oxide, aluminum oxide, and silicon carbide; The material of the piezoelectric layer is one of lithium niobate, potassium niobate, lithium tantalate, aluminum nitride, quartz, zinc oxide, and gallium oxide; The interdigital electrodes and the ohmic electrodes include a single layer or multiple layers of metal, and the metal material of the interdigital electrodes and the ohmic electrodes is one of gold, silver, copper, platinum, aluminum, molybdenum, titanium, and nickel.

3. The surface acoustic wave device according to claim 1, wherein The ratio of the thickness of the piezoelectric layer to the wavelength of the excited target elastic wave is less than 1 and greater than 0.

1.

4. The surface acoustic wave device according to claim 1, wherein The fingers of the interdigitated electrodes are parallel to each other, and the angle between the vertical direction of the fingers and the propagation direction of the target elastic wave is less than 40°.

5. A method for measuring carrier drift velocity using the surface acoustic wave device according to any one of claims 1 to 4, characterized in that: include: applying an AC voltage to the measuring device to measure a first insertion loss of the measuring device without a bias voltage; applying an AC voltage and DC bias voltages of different magnitudes to the measuring device, and measuring a second insertion loss of the measuring device under the different DC bias voltages; Calculating the difference between the second insertion loss and the first insertion loss under different DC bias voltages to obtain insertion loss change values ​​under different DC bias voltages, and obtaining a corresponding relationship between the insertion loss change value and the DC bias voltage; Based on the corresponding relationship between the insertion loss change value and the DC bias voltage, obtaining the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage; Based on the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage, the corresponding relationship between the carrier drift velocity and the DC bias voltage is obtained, and the carrier drift velocity measurement is completed.

6. The method according to claim 5, wherein Applying an AC voltage and DC bias voltages of different magnitudes to the measuring device, and measuring a second insertion loss of the measuring device under the different DC bias voltages, comprises: applying an AC voltage of a specified magnitude to the measuring device; Within a specified voltage range, DC bias voltages of different magnitudes are selected at equal intervals and applied to the measuring device in sequence, and the second insertion loss of the measuring device under different DC bias voltages is measured.

7. The method according to claim 5, wherein The obtaining of the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage based on the corresponding relationship between the insertion loss change value and the DC bias voltage includes: Based on the formula , deriving a corresponding relationship between the attenuation / gain coefficient and the DC bias voltage from the corresponding relationship between the insertion loss change value and the DC bias voltage; in, IL is the insertion loss change value, and α is the attenuation / gain coefficient.

8. The method according to claim 5, wherein The obtaining of the corresponding relationship between the carrier drift velocity and the DC bias voltage based on the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage includes: Based on the formula , deriving the corresponding relationship between the carrier drift velocity and the DC bias voltage from the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage; Among them, K 2 is the intrinsic electromechanical coupling coefficient, ω c is the dielectric relaxation frequency, ω D is the diffusion frequency, α is the attenuation / gain coefficient, is the diffusion length, is the wave vector, and γ is a variable used to reflect the relationship between the carrier drift velocity and the sound speed ratio.

9. The method according to claim 8, wherein The attenuation / gain factor α Calculated using the following formula: ； k = ω / v s ; oh c = σ / ε; ω D = v s 2 / D n ; γ = 1 - v dri / v s ; K 2 = and 2 / εc; in, γ is a variable used to reflect the relationship between the carrier drift velocity and the speed of sound, v s is the propagation velocity of sound waves, v dri is the carrier drift velocity, σ is the conductivity, ε is the dielectric constant, D n is the electron diffusion coefficient, ω is the angular frequency, and c is the speed of light.

10. The method according to claim 9, wherein Based on the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage, a corresponding relationship between the carrier drift velocity and the DC bias voltage is obtained. Before completing the carrier drift velocity measurement, the method further includes: A DC bias voltage is applied to the measuring device, and the current-voltage characteristic of the measuring device is measured to extract the conductivity σ.

Images