Surface acoustic wave device and method of measuring carrier drift velocity thereof

Abstract

The application relates to the technical field of semiconductors, and provides a surface acoustic wave device and a method for measuring carrier drift velocity of the surface acoustic wave device. The method comprises the following steps: applying an alternating voltage and different sizes of direct current bias voltages to a measurer, measuring second insertion loss of the measurer under different direct current bias voltages; calculating the difference between the second insertion loss and first insertion loss under different direct current bias voltages, obtaining an insertion loss change value under different direct current bias voltages, and obtaining the corresponding relationship between the insertion loss change value and the direct current bias voltage; based on the corresponding relationship between the insertion loss change value and the direct current bias voltage, obtaining the corresponding relationship between an attenuation / gain coefficient and the direct current bias voltage; and based on the corresponding relationship between the attenuation / gain coefficient and the direct current bias voltage, obtaining the corresponding relationship between the carrier drift velocity and the direct current bias voltage, and completing the carrier drift velocity measurement. The drift velocity continuous measurement can be realized under full electric field coverage.

Description

TECHNICAL FIELD

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

[0002] The performance of semiconductor materials determines the function and efficiency of various devices from consumer electronics to industrial systems. The application field of semiconductor devices has expanded from traditional integrated circuits to 5G communication, artificial intelligence, new energy, Internet of Things and other frontier fields, which puts higher requirements on the electronic transport properties of materials. The core performance of semiconductor materials depends on the transport behavior of carriers (electrons or holes), and the carrier drift velocity is an important parameter for studying the transport behavior of carriers. The measurement of carrier drift velocity is of great significance for revealing the microscopic mechanism of charge transport in materials and providing experimental verification for theoretical models.

[0003] Currently, the mainstream carrier drift velocity characterization techniques include 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 (such as only covering low field or high field) or subject to sample type and experimental conditions, and cannot achieve universal measurement of the carrier drift velocity-field relationship in the full electric field range.

[0004] Therefore, it is an urgent problem for those skilled in the art to explore a universal carrier drift velocity-field relationship measurement technique in a large dynamic electric field range. SUMMARY

[0005] Therefore, the embodiments of the present application provide a surface acoustic wave device and a method for measuring carrier drift velocity thereof, which can realize carrier drift velocity measurement in the full electric field range.

[0006] A first aspect of the embodiments of the present application provides a surface acoustic wave device, comprising:

[0007] a support substrate;

[0008] a dielectric layer located on the upper surface of the support substrate;

[0009] a piezoelectric layer located on the upper surface of the dielectric layer;

[0010] interdigital electrodes discretely arranged on both sides of the upper surface of the piezoelectric layer;

[0011] a semiconductor thin film layer located on the upper surface of the piezoelectric layer and arranged between the interdigital electrodes on both sides;

[0012] an ohmic electrode located on the upper surface of the piezoelectric layer and ohmically contacted on both sides of the semiconductor thin film.

[0013] In one embodiment, the material of the support substrate comprises at least one of silicon, silicon oxide, silicon carbide, sapphire, diamond, quartz, aluminum nitride, gallium nitride, gallium oxide, zinc oxide;

[0014] The material of the medium layer is one of silicon dioxide, silicon nitride, aluminum oxide, aluminum oxide, silicon carbide;

[0015] The material of the piezoelectric layer is one of lithium niobate, potassium niobate, lithium tantalate, aluminum nitride, quartz, zinc oxide, gallium oxide;

[0016] The interdigital electrode and the ohmic electrode comprise a single layer or multiple layers of metal, and the metal material of the interdigital electrode and the ohmic electrode is one of gold, silver, copper, platinum, aluminum, molybdenum, titanium, and nickel.

[0017] 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.

[0018] In one embodiment, the interdigital electrodes are parallel to each other, and the angle between the vertical direction of the interdigital electrodes and the propagation direction of the target elastic wave is less than 40°.

[0019] A second aspect of the embodiments of the present application provides a method for measuring carrier drift velocity by using the surface acoustic wave device provided by the first aspect of the embodiments of the present application, comprising:

[0020] An alternating voltage is applied to the surface acoustic wave device, and a first insertion loss of the surface acoustic wave device under no bias voltage is measured;

[0021] An alternating voltage and different sizes of direct current bias voltages are applied to the surface acoustic wave device, and second insertion losses of the surface acoustic wave device under different direct current bias voltages are measured;

[0022] The difference between the second insertion losses under different direct current bias voltages and the first insertion loss is calculated to obtain an insertion loss change value under different direct current bias voltages, and a corresponding relationship between the insertion loss change value and the direct current bias voltage is obtained;

[0023] Based on the corresponding relationship between the insertion loss change value and the direct current bias voltage, a corresponding relationship between an attenuation / gain coefficient and the direct current bias voltage is obtained;

[0024] Based on the corresponding relationship between the attenuation / gain coefficient and the direct current bias voltage, a corresponding relationship between the carrier drift velocity and the direct current bias voltage is obtained, and the measurement of the carrier drift velocity is completed.

[0025] In one embodiment, the application of the alternating voltage and the different sizes of the direct current bias voltages to the surface acoustic wave device to measure the second insertion losses of the surface acoustic wave device under different direct current bias voltages comprises:

[0026] applying an alternating voltage of a specified size to the surface acoustic wave device;

[0027] selecting different direct current bias voltages of different sizes at equal intervals within a specified voltage range, and sequentially applying the direct current bias voltages to the surface acoustic wave device, and measuring second insertion loss of the surface acoustic wave device under the different direct current bias voltages.

[0028] In one embodiment, the obtaining of the corresponding relationship between the attenuation / gain coefficient and the direct current bias voltage based on the corresponding relationship between the insertion loss variation value and the direct current bias voltage comprises:

[0029] deducing the corresponding relationship between the attenuation / gain coefficient and the direct current bias voltage from the corresponding relationship between the insertion loss variation value and the direct current bias voltage based on the formula ;

[0030] wherein, IL is the insertion loss variation value, and a is the attenuation / gain coefficient.

[0031] In one embodiment, the obtaining of the corresponding relationship between the carrier drift velocity and the direct current bias voltage based on the corresponding relationship between the attenuation / gain coefficient and the direct current bias voltage comprises:

[0032] deducing the corresponding relationship between the carrier drift velocity and the direct current bias voltage from the corresponding relationship between the attenuation / gain coefficient and the direct current bias voltage based on the formula ;

[0033] wherein, 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 for reflecting the ratio of the carrier drift velocity to the acoustic velocity.

[0034] In one embodiment, the attenuation / gain coefficient α is calculated by the formula

[0035] ;

[0036] k = ω / v s ;

[0037] ω c = σ / ε;

[0038] ω D = v s2 / D n ;

[0039] γ = 1 - v dri / v s ;

[0040] K 2 =e 2 / εc;

[0041] wherein, γ is a variable for reflecting the ratio of carrier drift velocity and sound velocity, v s is the propagation rate of the sound wave, 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.

[0042] In one embodiment, based on the corresponding relationship between the attenuation / gain coefficient and the direct current bias voltage, a corresponding relationship between the carrier drift velocity and the direct current bias voltage is obtained, and before the carrier drift velocity measurement is completed, the method further comprises:

[0043] applying a direct current bias voltage to the surface acoustic wave device, measuring the current-voltage characteristic of the surface acoustic wave device, and extracting the conductivity σ.

[0044] The second aspect of the embodiments of the present application provides a measurement method, which comprises: applying an alternating current voltage to the surface acoustic wave device, measuring a first insertion loss of the surface acoustic wave device under no bias voltage; applying an alternating current voltage and different sizes of direct current bias voltage to the surface acoustic wave device, measuring second insertion losses of the surface acoustic wave device under different direct current bias voltages; calculating the difference between the second insertion losses under different direct current bias voltages and the first insertion loss, obtaining an insertion loss change value under different direct current bias voltages, and obtaining a corresponding relationship between the insertion loss change value and the direct current bias voltage; based on the corresponding relationship between the insertion loss change value and the direct current bias voltage, obtaining a corresponding relationship between the attenuation / gain coefficient and the direct current bias voltage; and based on the corresponding relationship between the attenuation / gain coefficient and the direct current bias voltage, obtaining a corresponding relationship between the carrier drift velocity and the direct current bias voltage, and completing the carrier drift velocity measurement. By using the electro-acoustic interaction and adjusting the size of the applied bias voltage, the semiconductor carrier drift velocity can be measured at any bias voltage (i.e. in the full electric field range). By comparing the insertion loss changes of the bias-free reference state and the biased state, the system error of the device itself 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 require temperature variation operation, and the preparation process is compatible with the traditional CMOS process, which is conducive to large-scale use.

[0045] It can be understood that the beneficial effects of the first aspect described above can be seen in the relevant description of the second aspect, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0047] Figure 1 is a structural schematic diagram of a surface acoustic wave device provided by an embodiment of the present application;

[0048] Figure 2 is a radio frequency S parameter curve diagram of a semiconductor thin film without bias voltage provided by another embodiment of the present application;

[0049] Figure 3 is a flowchart of a carrier drift velocity measurement method based on a surface acoustic wave provided by another embodiment of the present application;

[0050] Figure 4 is an attenuation / gain-bias voltage curve diagram provided by an embodiment of the present application;

[0051] Figure 5 is a drift velocity-voltage curve diagram provided by an embodiment of the present application. DETAILED DESCRIPTION

[0052] In the following description, specific details are set forth in order to provide a thorough understanding of embodiments of the present application. However, persons of ordinary skill in the art will readily recognize that embodiments of the present application can be practiced without these specific details, in other instances, well-known structures, devices, circuits, and methods have not been described in detail in order to avoid obscuring the present application.

[0053] It should be noted that when an element is referred to as being "fixed" or "set" on another element, it can 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 can be directly connected to the other element or indirectly connected to the other element.

[0054] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like, indicating the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0055] In addition, in the description of the present application and the appended claims, the terms "first", "second", "third" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0056] It should be understood that when used in the present application specification and the appended claims, the term "comprising" indicates the presence of the described features, whole, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, whole, steps, operations, elements, components and / or sets thereof.

[0057] It should also be understood that the term "and / or" used in the present application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0058] In the present application specification, the reference "one embodiment" or "some embodiments" and the like means that the specific features, structures or characteristics described in connection with the embodiment are included in one or more embodiments of the present application. Therefore, the statements "in one embodiment", "in some embodiments", "in other some embodiments", "in further some embodiments" and the like appearing in different places in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized. The terms "include", "contain", "have" and their variants mean "include but not limited to", unless otherwise specifically emphasized.

[0059] As Figure 1 shown, a first aspect of the embodiments of the present application provides a surface acoustic wave device, comprising:

[0060] a support substrate 100;

[0061] a dielectric layer 200 located on the upper surface of the support substrate 100;

[0062] a piezoelectric layer 300 located on the upper surface of the dielectric layer 200;

[0063] an interdigital electrode 400 discretely arranged on both sides of the upper surface of the piezoelectric layer 300;

[0064] A semiconductor thin film layer 500 is located on the upper surface of the piezoelectric layer 300 and arranged between the two-sided interdigital electrodes 400;

[0065] An ohmic electrode 600 is located on the upper surface of the piezoelectric layer 300 and arranged to be in ohmic contact with the two sides of the semiconductor thin film.

[0066] In applications, the carrier drift velocity surface acoustic wave device based on surface acoustic wave provided by the application is used to measure the drift velocity of carriers in various semiconductor materials under bias voltage, and provides reliable experimental reference for electrical device design.

[0067] The discrete two-sided layout of the interdigital electrode in the embodiment of the application precisely limits the surface acoustic wave excitation area, the semiconductor thin film is placed in the core area of the sound wave propagation path, and the ohmic electrode directly contacts the two sides of the thin film to form a carrier acceleration channel. This design optimizes the electro-acoustic energy coupling efficiency, and the spatial matching of the surface acoustic wave propagation path and the carrier motion direction significantly improves the interaction strength, providing a physical basis for sensitive detection of drift velocity.

[0068] 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;

[0069] The material of the dielectric layer 200 is one of silicon dioxide, silicon nitride, aluminum oxide, aluminum oxide, and silicon carbide;

[0070] The material of the piezoelectric layer 300 is one of lithium niobate, potassium niobate, lithium tantalate, aluminum nitride, quartz, zinc oxide, and gallium oxide;

[0071] The interdigital electrode 400 and the ohmic electrode 600 include a single layer or multiple layers of metal, and the metal material of the interdigital electrode 400 and the ohmic electrode 600 is one of gold, silver, copper, platinum, aluminum, molybdenum, titanium, and nickel.

[0072] In one embodiment, the thickness of the piezoelectric layer 300 is less than 1 and greater than 0.1 times the wavelength of the excited target elastic wave.

[0073] In one embodiment, the interdigital electrodes in the interdigital electrode 400 are parallel to each other, and the angle between the vertical direction of the interdigital electrodes and the propagation direction of the target elastic wave is less than 40°.

[0074] In application, the semiconductor thin film layer can be any semiconductor material. The interdigital electrode and the ohmic electrode are composed of single layer or multiple layers of metal, and the metal composition of the two can be the same or different. The ohmic electrode is connected with the semiconductor thin film structure to form an ohmic contact. The number of interdigital electrodes is greater than 2, and the thickness of the dielectric layer is greater than or equal to 0. Specifically, the thickness of the dielectric layer can be 0-2um, the thickness of the semiconductor thin film can be 20nm-1000nm, and the length of the semiconductor thin film can be 10um-1000um.

[0075] Wherein, the propagation speed of the acoustic wave in the support substrate 100 is greater than the propagation speed of the acoustic wave in the piezoelectric layer 300. At this time, most of the energy of the excited surface acoustic wave is concentrated in the piezoelectric layer 300 during transmission; part of the energy is concentrated in the composite film formed by the upper surface of the support substrate 100, the dielectric layer 200 and the lower surface of the piezoelectric layer 300; a very small part of the energy will leak into the support substrate 100; at this time, since the equivalent wave speed in the composite film is greater than the equivalent wave speed in the piezoelectric layer, the wave speed of the excited acoustic wave can be effectively improved. At the same time, the introduction of the dielectric layer can effectively improve the temperature stability of the device and the parasitic capacitance effect under the radio frequency working environment.

[0076] The application further provides a preparation method of a carrier drift velocity surface acoustic wave device based on a surface acoustic wave, and the preparation method comprises the following steps:

[0077] Step 101: providing a high-wave-speed support substrate 100.

[0078] In application, the 4H-SiC substrate with (001) crystal direction is cleaned.

[0079] Step 102: forming a dielectric layer 200 on the upper surface of the high-wave-speed substrate.

[0080] In application, the silicon dioxide / lithium niobate structure is transferred to the substrate by ion cutting hetero-integration technology.

[0081] Step 103: forming a piezoelectric layer 300 on the upper surface of the dielectric layer.

[0082] Step 104: forming a semiconductor thin film layer 500, an interdigital electrode 400 and an ohmic electrode 600 on the upper surface of the piezoelectric layer.

[0083] In application, the pattern of the semiconductor thin film is formed on the lithium niobate by coating, photoetching and developing, and the gallium oxide thin film is further deposited by MOCVD. The period distribution pattern of the interdigital electrode is formed on both sides of the semiconductor thin film by coating, photoetching and developing, and the metal Al is further evaporated by electron beam evaporation. The pattern of the ohmic electrode is formed on both sides of the semiconductor thin film by coating, photoetching and developing, and the high-doped layer is obtained by ion implantation and high-temperature activation. The process of forming the pattern of the ohmic electrode on both sides of the semiconductor thin film is repeated, and the metal Ti / Au is evaporated by electron beam evaporation, and the ohmic contact is strengthened by rapid annealing.

[0084] In application, the medium layer 200, the piezoelectric layer 300 and the semiconductor thin film layer 500 can be prepared by HVPE, MOCVD, Mis-CVD, wafer bonding and the like; the interdigital electrode and the ohmic electrode can be prepared on the piezoelectric layer by photoetching, developing, electron beam evaporation, stripping or electron beam evaporation, photoetching, developing and etching; and the ohmic contact between the ohmic electrode and the semiconductor thin film layer can be strengthened by rapid thermal annealing.

[0085] In the embodiment of the present application, the piezoelectric layer is formed on the high sound velocity substrate, the binding effect of the piezoelectric layer on energy is enhanced, and the center frequency and the effective electromechanical coupling coefficient of the device are effectively improved.

[0086] In one embodiment, the acoustic surface wave device with the following structure can be prepared by the preparation method: the material of the support substrate 100 includes silicon carbide, and the thickness is greater than 300 um; the material of the medium layer 200 is silicon dioxide, and the thickness t1 is 20-75 nm; the material of the piezoelectric layer 300 is lithium niobate, and the thickness t2 is 200-400 nm; the material of the semiconductor thin film layer is gallium oxide, the thickness t is 150-300 nm, and the length L2 in the sound wave propagation direction is 20-30 um. The material of the interdigital electrode is Al, and the thickness is 80 nm; the material of the ohmic electrode is Ti / Au, and the thickness is 20 nm / 80 nm, and the width b in the sound wave propagation direction is 10 um; the period λ (the wavelength of the sound wave) of the interdigital electrode is 4 um, the distance p between the centers of adjacent interdigital electrodes is 2 um, and the width a of the interdigital electrode is 1 um; the distance L1 from the period boundary of the interdigital electrode to the ohmic electrode is 10 um; and the logarithm of the two end interdigital electrodes is 10.

[0087] In order to quickly illustrate the effect of the embodiment, the radio frequency S parameters of the device of the embodiment are simulated by finite element simulation, as shown in Figure 2 The center frequency of the device is about 1.5 GHz, the minimum insertion loss is 5.2 dB, and the maximum reflection loss is 10 dB, which indicates that the device has good performance and fully meets the measurement requirements.

[0088] In actual experiments, the carrier drift velocity measurement structure and preparation steps described above are used to prepare a device to be measured, and then the carrier drift velocity is measured based on a vector network analyzer and a source table. The measurement mechanism of the carrier drift velocity surface acoustic wave device based on the embodiment of the application is as follows:

[0089] An excitation electric field is applied to one end of the interdigital electrode, and a surface acoustic wave is excited in the structure due to the piezoelectric effect. The phase of the surface acoustic wave is a quantity related to time and position. The real part of the wave vector k of the surface acoustic wave is related to the sound velocity, and the imaginary part is related to the attenuation of the surface acoustic wave. At the same time, the surface acoustic wave excited will be accompanied by the generation of potential fluctuations during propagation. When a semiconductor thin film exists in the propagation path of the surface acoustic wave, the potential fluctuations accompanying the propagation of the surface acoustic wave will interact with the free carriers in the semiconductor, that is, electro-acoustic interaction. The electro-acoustic interaction will destroy the thermal equilibrium state in the semiconductor thin film and cause redistribution of the carriers. Similarly, the redistribution of the carriers will also modulate the propagating surface acoustic wave, and the state of the carriers can be extracted from the surface acoustic wave. The greater the difference between the motion state of the carriers in the semiconductor and the surface acoustic wave, the stronger the modulation feedback effect. When a bias voltage is applied to the two sides of the semiconductor thin film along the direction of the surface acoustic wave propagation, the free carriers will be accelerated in the same direction or in the opposite direction, and the motion state of the carriers will be sharply changed. Through electro-acoustic interaction, the velocity state of the free carriers is transmitted back to the surface acoustic wave. The final effect is that 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 finally the attenuation / gain coefficient α is obtained as follows:

[0090]

[0091] 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 , equation (1.1) can be written as:

[0092]

[0093] 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 acoustic 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 equation (1.2), it can be seen that the sign of α is determined only by γ. When γ is greater than 0, i.e., the carrier drift velocity is greater than the acoustic wave propagation velocity, α is also greater than 0, and the acoustic wave is amplified. Conversely, when γ is less than 0, i.e., the carrier drift velocity is less than the acoustic wave propagation velocity, α is also less than 0, and the acoustic wave is attenuated. In equation (1.1), k, ω c , ω D , K 2 are parameters related only to the material properties and the device structure, and are constant values that can be determined, and only γ is a variable, so the attenuation / gain coefficient is a function related only to the carrier drift velocity. Further, solving equation (1.2) for α γ yields:

[0094]

[0095] The carrier drift velocity can be easily obtained from γ. Therefore, in actual operation, the attenuation / gain coefficient can be measured as a function of the bias voltage across the semiconductor thin film, the carrier drift velocity can be calculated using equation (1.3), and ultimately a set of curves of the carrier drift velocity as a function of the direct current bias voltage can be obtained, i.e., full-range measurement of the carrier drift velocity is achieved.

[0096] As shown in FIG. 1, embodiments of the present application also provide a method for measuring the carrier drift velocity using the surface acoustic wave device according to any of the above embodiments, which comprises: Figure 3 Step 1: Apply an alternating voltage to the surface acoustic wave device, and measure the first insertion loss of the surface acoustic wave device under no bias voltage.

[0097]

[0098] ​In application, the vector network analyzer is calibrated to ensure the measurement result is true and reliable. Then the surface acoustic wave device is placed on the probe station, and an AC signal is applied to any port of the surface acoustic wave device, and the other port is used as the signal output port. The first insertion loss of the surface acoustic wave device under no bias voltage is measured by using the calibrated vector network analyzer.

[0099] Step 2: An AC voltage and different sizes of DC bias voltage are applied to the surface acoustic wave device, and the second insertion loss of the surface acoustic wave device under different DC bias voltages is measured.

[0100] In application, the DC probe is inserted into the ohmic electrode at both ends of the prepared semiconductor to provide a DC bias voltage. The size of the DC bias voltage is different DC bias voltages selected at equal intervals in a specified voltage range. The specified voltage range can be adjusted arbitrarily according to the measurement requirements to realize full-field range measurement.

[0101] Step 3: The difference between the second insertion loss and the first insertion loss under different DC bias voltages is calculated to obtain the insertion loss change value under different DC bias voltages, and the corresponding relationship between the insertion loss change value and the DC bias voltage is obtained.

[0102] In application, the insertion loss change value is the difference between the second insertion loss and the first insertion loss under different DC bias voltages. According to different DC bias voltages, multiple second insertion losses can be measured, so that multiple insertion loss change values can be calculated, and the corresponding relationship between the insertion loss change value and the DC bias voltage can be obtained.

[0103] 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.

[0104] Step 5: Based on the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage, the corresponding relationship between the carrier drift speed and the DC bias voltage is obtained, and the carrier drift speed measurement is completed.

[0105] In one embodiment, an AC voltage and different sizes of DC bias voltage are applied to the surface acoustic wave device, and the second insertion loss of the surface acoustic wave device under different DC bias voltages is measured, comprising:

[0106] A specified size of AC voltage is applied to the surface acoustic wave device.

[0107] In a specified voltage range, different sizes of DC bias voltage are selected at equal intervals and applied to the surface acoustic wave device in turn, and the second insertion loss of the surface acoustic wave device under different DC bias voltages is measured.

[0108] In one embodiment, the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage is obtained based on the corresponding relationship between the insertion loss change value and the DC bias voltage, including:

[0109] 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 based on the formula

[0110] wherein, IL is the insertion loss change value, and a is the attenuation / gain coefficient.

[0111] In one embodiment, the corresponding relationship between the carrier drift velocity and the DC bias voltage is obtained based on the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage, including:

[0112] The corresponding relationship between the carrier drift velocity and the DC bias voltage is derived from the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage based on the formula

[0113] wherein, 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 for reflecting the ratio of the carrier drift velocity to the sound velocity.

[0114] In one embodiment, the attenuation / gain coefficient a α is calculated by the following formula:

[0115] ;

[0116] k = ω / v s ;

[0117] ω c = σ / ε;

[0118] ω D = v s 2 / D n ;

[0119] γ = 1 - v dri / v s ;

[0120] K 2 =e 2 / εc;

[0121] wherein,​​γ is a variable for reflecting the ratio of carrier drift velocity and acoustic velocity, v s is the propagation rate of acoustic wave, 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, c is the speed of light.

[0122] In one embodiment, 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 before the carrier drift velocity measurement is completed, the method further comprises:

[0123] The DC bias voltage is applied to the surface acoustic wave device, the current-voltage characteristic of the surface acoustic wave device is measured, and the conductivity σ is extracted.

[0124] In one embodiment, the carrier drift velocity measurement process is demonstrated by numerical calculation, as shown in Figure 4 The attenuation / gain coefficient of the electro-acoustic interaction is shown in the figure, 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 dashed line is the result of introducing nonlinear effects. It can be found that due to the existence of nonlinear effects, the attenuation / gain will decrease on the high voltage side. As shown in Figure 5 The carrier drift velocity-voltage relationship curve calculated based on the attenuation / gain coefficient in Figure 4 The black solid line in the figure shows that the carrier drift velocity-voltage is a perfect linear relationship, which is consistent with the assumption; the black dashed line is the calculation result of introducing nonlinear effects, which is also consistent with the assumption.

[0125] In summary, the measurement process is not limited by the voltage range, the type of material, the relationship between the carrier drift velocity and the voltage, and other factors, so the universal measurement of the carrier drift velocity-electric field relationship of any material in the entire range can be realized, and the technical barriers in the current carrier measurement field are effectively solved.

[0126] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A surface acoustic wave device, characterized by, The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method.

2. The SAW device of claim 1, wherein, The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method.

3. The SAW device of claim 1, wherein, The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method.

4. The SAW device of claim 1, wherein, The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method.

5. A method for measuring a carrier drift velocity using the surface acoustic wave device according to any one of claims 1 to 4, characterized by The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method.

6. The method of claim 5, wherein, The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method.

7. The method of claim 5, wherein, The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. Based on the formula deduce the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage from the corresponding relationship between the insertion loss variation value and the DC bias voltage; wherein The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. is the insertion loss variation value, and a is the attenuation / gain factor.

8. The method of claim 5, wherein, The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. Based on the formula a corresponding relationship between the carrier drift velocity and the DC bias voltage is derived from the corresponding relationship between the attenuation / gain coefficient and the DC bias voltage; where K 2 is the intrinsic electro-mechanical 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 ratio of carrier drift velocity and sound velocity.

9. The method of claim 8, wherein, the attenuation / gain factor α The calculation is made by 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; wherein, The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. is a variable for reflecting a ratio relationship of carrier drift velocity and sound velocity, v s is a propagation rate of a sound wave, v dri is a carrier drift velocity, σ is an electrical conductivity, ε is a dielectric constant, D n is an electron diffusion coefficient, ω is an angular frequency, and c is a light speed.

10. The method of claim 9, wherein, The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoelectric layer and a piezoelectric layer manufacturing method. The application relates to a piezoe A direct current bias voltage is applied to the surface acoustic wave device, a current-voltage characteristic of the surface acoustic wave device is measured, and a conductivity σ is extracted.

Images