A method of measuring intrinsic carrier mobility of a semiconductor material

Abstract

The application discloses a kind of methods for measuring intrinsic carrier mobility of semiconductor material, it is related to semiconductor material performance measurement technical field;The method comprises the following steps: building the measurement system of intrinsic carrier mobility of semiconductor material;Using optical delay line constantly changes the relative time delay between probe light and pump light, and obtains the probe light intensity under the action of pump light and without the action of pump light, test obtains the transient reflection dynamics spectrum of semiconductor material, and extracts to obtain Brillouin oscillation signal;Based on Brillouin oscillation signal, calculate electron deformation potential, hole deformation potential, semiconductor material elastic modulus;Based on electron deformation potential, hole deformation potential and semiconductor material elastic modulus, the intrinsic carrier (electron and hole) mobility of semiconductor material is calculated to obtain.For the current lack of a kind of method capable of experimental measurement material intrinsic carrier mobility, the measuring method in the application fills the gap in the field.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor material performance measurement, and in particular relates to a method for measuring the intrinsic carrier mobility of a semiconductor material. Background Art

[0002] Carrier mobility is one of the determining factors for the carrier diffusion length in semiconductor materials and a key parameter affecting the performance of semiconductor devices. Factors influencing perovskite carrier mobility can be divided into two categories: intrinsic and extrinsic. Intrinsic factors are primarily electron-lattice coupling (electron-phonon scattering) in the material, which depends on the inherent properties of the material (such as its structure) and is unavoidable. Extrinsic factors, such as electron-defect scattering and carrier-carrier scattering, are closely related to the material's preparation process and carrier concentration. The carrier mobility affected only by intrinsic factors is the material's intrinsic carrier mobility, the optimal carrier mobility that the material can achieve under specific operating temperature conditions. Quantitatively determining the intrinsic carrier mobility of semiconductor materials and defining the limits of the material's carrier transport performance can guide semiconductor material design, thin film preparation, and device structure optimization, and is of great significance for the development of high-performance semiconductor devices.

[0003] Methods for measuring carrier mobility can be divided into two main categories: electrical characterization methods, such as the Hall effect, time-of-flight, and space-charge-limited current; and non-contact methods, such as terahertz spectroscopy. Compared to electrical measurement methods, non-contact methods avoid interference from metal-semiconductor contact and better reflect the material's carrier transport properties. Terahertz spectroscopy has been widely used to measure carrier mobility in semiconductor materials. This technique not only extracts carrier mobility through changes in terahertz transmittance but also analyzes defect state density and carrier recombination processes through photoconductive dynamics analysis. However, because the influence of extrinsic factors such as defects cannot be eliminated, the carrier mobility measured by terahertz spectroscopy reflects the actual carrier mobility that results from the combined effects of intrinsic and extrinsic factors, rather than the intrinsic carrier mobility of the material. In summary, there is currently a lack of experimental methods that can experimentally measure the intrinsic carrier mobility of materials.

[0004] To address the technical issues existing in the prior art, the present invention proposes a non-contact method for measuring the elastic modulus of materials based on femtosecond transient spectroscopy. This method uses femtosecond laser pulses to excite a semiconductor material, generating a thermoelastic pressure. This pressure then propagates into the material. By detecting the pulses at different times, the Brillouin oscillation frequency of the material is detected, allowing the elastic modulus of the material along the propagation direction to be calculated, and further, the intrinsic carrier mobility (electrons and holes) of the semiconductor material to be calculated. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for measuring the intrinsic carrier mobility of semiconductor materials, so as to solve the problem that the existing experimental method for measuring the carrier mobility of materials proposed in the above background technology measures the actual carrier mobility that is the result of the combined action of intrinsic and non-intrinsic factors, rather than the intrinsic carrier mobility of the material. At present, there is still a lack of an experimental method that can experimentally measure the intrinsic carrier mobility of materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for measuring the intrinsic carrier mobility of a semiconductor material, comprising the following steps:

[0008] S1. Select semiconductor materials as samples, build a measurement system for the intrinsic carrier mobility of semiconductor materials, and use femtosecond laser pulses to excite the semiconductor materials;

[0009] S2. Detecting the Brillouin oscillation signal using a measurement system: Using an optical delay line to continuously change the relative time delay between the probe light and the pump light, and obtaining the probe light intensity with and without the pump light, the transient reflection dynamics spectrum of the semiconductor material is measured; and the Brillouin oscillation signal is extracted based on the transient reflection dynamics spectrum.

[0010] S3. Based on the Brillouin oscillation signal, obtain the elastic modulus of the semiconductor material, the relative defect state density of the semiconductor material, and calculate the electron deformation potential and hole deformation potential;

[0011] S4. Based on the electron deformation potential, hole deformation potential and elastic modulus of the semiconductor material, the intrinsic carrier mobility of the semiconductor material is calculated.

[0012] Preferably, the S1 is as follows:

[0013] Measurement system, including: femtosecond laser, beam splitter, reflector, convex lens, sapphire crystal Sapphire, OPA system, optical delay line ODL, spectrometer;

[0014] The 800nm ​​femtosecond pulse light with a repetition rate of 1kHz emitted from the femtosecond laser is divided into a detection light path and a pump light path through a beam splitter;

[0015] After entering the OPA system, the pump light is modulated into high-energy monochromatic pulse light with a repetition rate of 500 Hz and a wavelength of 400 nm or any wavelength in the range of 460 to 700 nm. After reflection and focusing, the modulated pump light converges on the sample.

[0016] The probe light enters the optical delay line (ODL) to control the time delay between the pump light and the probe light. After emitting from the optical delay line (ODL), the probe light is focused onto the sapphire crystal (Sapphire) to generate supercontinuum white light. The supercontinuum white light is then divided into a reference light path and a probe light path by a beam splitter.

[0017] After being reflected and focused, the reference light finally enters the spectrometer;

[0018] The detection light is focused on the sample and spatially overlaps with the pump light. The detection light carrying the sample information reflected by the sample surface is reflected and focused, and finally enters the spectrometer.

[0019] Preferably, the S2 is as follows:

[0020] The repetition rate of the pump light was modulated to 500 Hz, and the repetition rate of the probe light was maintained at 1 kHz, with a cycle of 2 ms. During the first 1 ms of a cycle at time 0, the intensity of the probe light with the pump light was obtained because the probe light and pump light overlapped. During the second 1 ms of the same cycle, the intensity of the probe light without the pump light was obtained.

[0021] Calculate the transient reflectivity change of the semiconductor material surface at time 0 Amplitude, as follows:

[0022]

[0023] in, is the intensity of the reflected light at wavelength λ at time t after pump excitation; is the intensity of the reflected light at wavelength λ when there is no pump;

[0024] Based on time 0, the optical path of the probe light is extended to detect the transient reflectivity change amplitude after the pump light acts on it for x ps. Similarly, by using an optical delay line to continuously change the relative time delay between the probe light and the pump light, the complete transient reflectivity dynamic spectrum of the semiconductor material is tested.

[0025] The carrier signal background is obtained by a smoothing function based on the adjacent averaging method, and the Brillouin oscillation signal is obtained by subtracting the carrier signal background from the raw data of the transient reflection dynamics spectrum.

[0026] Preferably, the electron deformation potential and hole deformation potential calculated in S3 are specifically:

[0027] The same sample is excited by the excitation light of hv1 and hv2 with the same excitation photon number density N. g >>E g -Et When the amplitude ratio of the two Brillouin oscillation signals is measured, the deformation potential pressure σ is obtained. d and the thermoelastic pressure σ under two excitation conditions T1 and σ T2 The expression is:

[0028]

[0029] Under the same excitation conditions, the following relationship is obtained for two single crystal samples with different defect state densities, n and εn:

[0030]

[0031] σ d1 -σ d2 =(1-ε)nd h

[0032] σ d1 =-Nd e -(Nn)d h

[0033] Among them, σ T1 and σ T2 is the thermoelastic pressure of two semiconductor materials under the same excitation conditions, σ d1 and σ d2 is the deformation potential pressure of the two semiconductor materials; ε is the known relative defect state density coefficient;

[0034] The electron deformation potential d is obtained in turn e , hole deformation potential d h , electron defect state density n.

[0035] Preferably, the S4 is specifically as follows:

[0036] The intrinsic carrier mobility of semiconductor materials is calculated as follows:

[0037]

[0038] Where, μ is the intrinsic carrier mobility; is the reduced Planck constant, e is the elementary charge, k b is the Boltzmann constant, T is the absolute temperature, m* is the effective mass of the electron or hole (can be obtained by consulting the literature); C is the elastic modulus along the crystal axis; d is the deformation potential of the electron or hole, and when describing the intrinsic electron mobility, d is d e , when describing the intrinsic hole mobility, d is d h When calculating the intrinsic carrier mobility of electrons or holes, it is necessary to substitute the effective mass m* and deformation potential d of the corresponding type of carrier into the above formula.

[0039] Preferably, the elastic pressure of the semiconductor material along the transmission direction is calculated based on the electron deformation potential and the hole deformation potential, as follows:

[0040] The elastic pressure generated by the photoexcited semiconductor material is proportional to the initial amplitude of the Brillouin oscillation signal in the time domain. The elastic pressure σ includes the thermoelastic pressure σ T and deformation potential pressure σ d ;Right now

[0041]

[0042] σ d =-(Nn)d h -Nd e

[0043]

[0044] Where B and β are the known bulk elastic modulus and linear expansion coefficient, respectively, and C p is the known heat capacity of the material; n is the electron defect state density; hv represents the excitation photon energy, N represents the excitation photon density, hv and N are experimental parameters; E g -E t represents the energy difference between the defect state and the bottom of the conduction band; d e represents the electron deformation potential, d h represents the hole deformation potential.

[0045] Preferably, the elastic modulus of the semiconductor material is obtained in S3, specifically:

[0046] The time-domain Brillouin scattering technique is used to measure semiconductor materials. The Brillouin oscillation signal under different crystal orientations is obtained. The oscillation frequency is extracted and the elastic modulus of the corresponding material is given. The elastic modulus C is expressed as:

[0047] C=f 2 λ 2 ρ / (4n 2 )

[0048] Where λ is the experimental detection wavelength, f is the Brillouin oscillation frequency, n is the refractive index of the material at the detection wavelength, and ρ is the material density. By measuring the Brillouin oscillation frequency f at a specific detection wavelength λ, the elastic modulus of the material in that incident direction can be determined.

[0049] Preferably, the relative defect state density characterization of the semiconductor material is obtained in S3, specifically:

[0050] Time-domain Brillouin scattering technology is used to characterize the Brillouin oscillation signals of samples with different defect state densities. Based on the fact that the Brillouin oscillation relaxation rate is proportional to the material defect state density, the ratio of the material's defect state density can be inferred from the ratio of its Brillouin oscillation relaxation rates.

[0051] Preferably, the energy difference E between the defect state and the conduction band bottom is g -E t , specifically:

[0052] Transient absorption spectroscopy technology is used to test the transient absorption spectrum signals of various semiconductor single crystal materials, determine the bleaching peaks corresponding to the defect state energy level and the conduction band bottom, and calculate the energy difference between the defect state energy level and the conduction band bottom.

[0053] In a second aspect, the present invention proposes a measurement system used in the method, comprising: a femtosecond laser, a beam splitter, a reflector, a convex lens, a sapphire crystal Sapphire, an OPA system, an optical delay line (ODL), and a spectrometer;

[0054] There are two beam splitters, namely a first beam splitter S1 and a second beam splitter S2;

[0055] There are 17 reflectors, namely the first reflector M1 to the seventeenth reflector M17;

[0056] There are seven convex lenses, namely a first convex lens L1 to a seventh convex lens L7.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) Traditional experimental methods cannot experimentally measure the intrinsic carrier mobility of materials. The present invention provides a method for experimentally measuring the intrinsic carrier mobility of materials, which makes it possible to experimentally measure the intrinsic carrier mobility, thereby giving the limit of the material's carrier transport performance, and further providing guidance for the preparation of semiconductor materials and the optimization of device performance.

[0059] (2) In the present invention, the key parameters required for determining the intrinsic carrier mobility of electrons and holes (material electron deformation potential, hole deformation potential, elastic modulus) are measured by extracting and analyzing transient reflection dynamics, breaking the limitation of relying on theoretical calculations to roughly estimate the intrinsic carrier (electron and hole) mobility, making it possible to experimentally measure the intrinsic carrier (electron and hole) mobility, filling the gap in the field. The experimental measurement of the intrinsic carrier mobility of the material can quantitatively evaluate the influence of non-intrinsic factors such as defects on the carrier mobility characteristics, providing guidance for material optimization.

[0060] (3) The present invention measures semiconductor materials through a measuring system, and can measure multiple properties of semiconductor materials such as intrinsic carrier mobility, elastic pressure, elastic modulus, relative defect state density, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 Schematic diagram of the structure of the measurement system in the present invention. DETAILED DESCRIPTION

[0062] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0063] Example 1:

[0064] The method for measuring the intrinsic carrier mobility of semiconductor materials mainly includes the following steps:

[0065] Step 1: Build a measurement system for the intrinsic carrier mobility of semiconductor materials;

[0066] The measurement system includes a femtosecond laser, a beam splitter, a reflector, a convex lens, a sapphire crystal Sapphire, an OPA system, an optical delay line ODL, and a spectrometer. Among them, there are two beam splitters, namely the first beam splitter S1 and the second beam splitter S2; there are 17 reflectors, namely the first reflector M1 to the seventeenth reflector M17; there are seven convex lenses, namely the first convex lens L1 to the seventh convex lens L7, as shown in FIG. Figure 1 shown.

[0067] The measurement system operates as follows: 800nm ​​femtosecond pulses with a repetition rate of 1kHz, emitted from a femtosecond laser, are first split into a detection path and a pump path by the first beamsplitter S1. The pump light, upon entering the OPA system, is modulated into high-energy monochromatic pulses with a repetition rate of 500Hz and a wavelength of 400nm or any wavelength in the 460-700nm range. The modulated pump light is reflected by the first and second mirrors M1 and M2, and focused by the first convex lens L1, ultimately converging on the sample.

[0068] The probe light is reflected by the third and fourth mirrors M3 and M4 before entering the optical delay line (ODL) to control the time delay between the pump and probe light. After emitting from the ODL, the probe light is redirected by a mirror group consisting of a fifth and sixth mirrors M5 and M6, and ultimately focused by the second convex lens L2 onto a sapphire crystal (Sapphire) to produce supercontinuum white light. The supercontinuum white light is collimated by the third convex lens L3, redirected by a mirror group consisting of a seventh, eighth, and ninth mirrors M7, M8, and M9, and then split into a reference and probe light path by the second beam splitter S2.

[0069] The reference light is redirected by a reflector group consisting of a tenth reflector M10 and an eleventh reflector M11 and then focused by a fourth convex lens L4 and finally enters the spectrometer.

[0070] The detection light is focused on the sample Sample through the fifth convex lens L5 and spatially overlaps with the pump light; the detection light carrying the sample information after being reflected by the sample surface is reflected by the mirror group consisting of the twelfth reflector M12, the thirteenth reflector M13, the fourteenth reflector M14, the fifteenth reflector M15, the sixteenth reflector M16 and the seventeenth reflector M17, and is collimated by the sixth convex lens L6 and focused by the seventh convex lens L7, and finally enters the spectrometer.

[0071] Step 2: Using a measurement system to detect the Brillouin oscillation signal;

[0072] 1) Measure the transient reflectivity change of semiconductor material surface;

[0073] For the detection of Brillouin oscillation signals, since the repetition frequency of the pump light is modulated to 500Hz after entering the OPA in the present invention, and the repetition frequency of the detection light remains at the original 1kHz, 2ms can be regarded as a cycle. Assuming that in the first 1ms of a cycle at time 0, since the detection light and the pump light achieve temporal overlap, it is equivalent to having the pump light and the detection light acting on the material surface at the same time. At this time, the spectrometer detects the intensity of the detection light reflected after the pump light modulates the reflectivity of the sample surface; then, in the second 1ms of the same cycle, since the repetition frequency of the pump light is only 500Hz, the material surface is only affected by the detection light but not the pump light. That is, the spectrometer detects the intensity of the detection light reflected when the reflectivity of the material surface is not modulated. Thus, the detection light intensity with and without the action of pump light is obtained.

[0074] Substituting the obtained detection light intensity into the following formula (1), the transient reflectivity change of the material surface at time 0 can be calculated: Amplitude.

[0075]

[0076] in, is the intensity of the reflected light at wavelength λ at time t after pump excitation; is the intensity of the reflected light at wavelength λ when there is no pump.

[0077] 2) Measure the complete transient reflection dynamics spectrum of semiconductor materials;

[0078] In order to obtain a complete transient reflection dynamics spectrum, it is necessary to change the time difference between the detection light and the pump light reaching the material surface. For this purpose, the present invention uses an optical delay line (ODL) in the detection light path to achieve a time delay relative to the pump light by increasing the optical path of the detection light.

[0079] Assume that at time 0, the optical path of the probe light is extended so that the probe light pulse arrives at the sample surface 1 ps after the pump light pulse arrives at the material surface. At this time, detection is performed to obtain the transient reflectivity change amplitude 1 ps after the pump light acts. Similarly, by using an optical delay line to continuously change the relative time delay between the probe light and the pump light, the complete transient reflection dynamics spectrum of the semiconductor material can be tested.

[0080] 3) Calculate the Brillouin oscillation signal;

[0081] Because the excitation light energy is higher than the material band gap, the pump pulse excites the material surface, generating deformation potential stress and thermal expansion stress that promote the generation of coherent acoustic phonons (CAP). The CAP modulates the local dielectric constant, forming an optical interface that moves from the sample surface to the interior of the crystal at the speed of sound v. This movement of the optical interface changes the local refractive index and reflects the probe light that penetrates the material. The probe light reflected from the material surface and the probe light reflected from the optical interface meet the interference conditions and interfere with each other. At the same time, because this optical interface propagates into the crystal at a certain speed of sound v, the phase difference between the probe light reflected from the surface and the probe light reflected from the optical interface varies linearly with time. Therefore, the resulting transient reflection dynamics spectrum is superimposed with a sinusoidally varying Brillouin oscillation signal induced by the CAP.

[0082] In order to extract the CAP signal (oscillation signal) in TR dynamics, the present invention obtains the carrier signal background by using a smoothing function based on the neighboring average method, and obtains a pure Brillouin oscillation signal by subtracting the carrier signal background from the original data.

[0083] Step 3: Calculate various parameters such as electron deformation potential, hole deformation potential, and elastic modulus of semiconductor materials;

[0084] The elastic pressure (σ) generated by the photoexcited semiconductor material is proportional to the initial amplitude of the Brillouin oscillation signal in the time domain, that is,

[0085]

[0086] Among them, B and β are the bulk elastic modulus and linear expansion coefficient respectively (can be obtained from the literature), C p is the heat capacity of the material (a parameter that can be obtained from the literature); n is the electron defect state density; the thermoelastic pressure σ T for Deformation potential pressure σ d (-(Nn)d h -Nd e ).

[0087] When the excitation photon energy (hv, experimental parameters), excitation photon density (N, experimental parameters), elastic modulus (C), energy difference between defect state and conduction band bottom (E g -E t ), the following steps can be used to give the deformation potential d of electrons and holes respectively. e and d h :

[0088] The same sample is excited by the excitation light with the same photon energy of hv1 and hν2. g >>E g -E t When the amplitude ratio of the two oscillation signals α is measured experimentally, the deformation potential pressure σ can be given. d and the thermoelastic pressure σ under two excitation conditions T1 and σ T2 The expression is:

[0089]

[0090] Furthermore, under the same excitation conditions, for two single crystal samples with different defect state densities, n and εn (ε is the relative defect state density coefficient, assumed to be known), the following relationship is obtained:

[0091]

[0092] σ d1 -σ d2 =(1-ε)nd h (7)

[0093] σ d1 =-Nd e -(Nn)d h (8)

[0094] Among them, σ T-1 and σ T-2is the thermoelastic pressure of two materials under the same excitation conditions, σ d1 and σ d2 is the deformation potential pressure of the two materials. From formulas (6) to (8), the electronic deformation potential d can be obtained in turn. e , hole deformation potential d h , defect state density n.

[0095] In the above analysis, the elastic modulus (C), the energy difference between the defect state and the conduction band bottom (E g -E t ) and the relative defect state density (ε) of the material need to be measured experimentally. This paper will introduce the experimental measurement schemes of these three parameters respectively:

[0096] In this embodiment, the elastic modulus of the semiconductor material is extracted:

[0097] The elastic modulus of a material can be expressed as C = f 2 λ 2 ρ / (4n 2 )(λ is the experimental detection wavelength, f is the Brillouin oscillation frequency, n is the refractive index of the material at the corresponding detection wavelength, and ρ is the material density, all of which can be obtained from literature.) It can be seen that by measuring the Brillouin oscillation frequency f at a specific detection wavelength λ, the elastic modulus of the material in that incident direction can be determined.

[0098] Time-domain Brillouin scattering technology is used to measure semiconductor materials, obtain Brillouin oscillation signals under different crystal orientation conditions, extract the oscillation frequency, and give the elastic modulus of each material.

[0099] In this embodiment, the relative defect state density of the semiconductor material is characterized by:

[0100] The Brillouin oscillation relaxation rate is proportional to the material's defect state density. Comparing the Brillouin oscillation relaxation rates of different semiconductor materials can reveal the ratio of their defect state densities. Time-domain Brillouin scattering (TDBS) will be used to characterize the Brillouin oscillation signals of samples with varying defect state densities. The ratio of the materials' oscillation relaxation rates can be used to infer their defect state density ratios.

[0101] In this embodiment, the energy difference between the conduction band bottom and the defect state energy level is characterized by:

[0102] According to literature, charge filling of the conduction band and defect states in semiconductor materials will cause ground-state bleaching in the transient absorption spectrum signal. The difference in the bleaching peak positions of the two can be used to estimate the energy difference between the defect state and the conduction band bottom. Transient absorption spectroscopy is used to measure the transient absorption spectrum signals of various semiconductor single crystal materials, identify the bleaching peaks corresponding to the defect state energy level and the conduction band bottom, and estimate the energy difference between the defect state energy level and the conduction band bottom.

[0103] In summary, by substituting the above calculated parameters into formula (2), the elastic pressure of the semiconductor material along the transmission direction can be calculated.

[0104] Step 4, calculating the intrinsic carrier mobility of the semiconductor material;

[0105] The intrinsic carrier mobility of semiconductor materials can be experimentally measured by the following methods:

[0106] Substituting the electron (hole) deformation potential and elastic modulus into formula (9) can give the intrinsic carrier mobility of the material.

[0107]

[0108] in, is the reduced Planck constant, e is the elementary charge, k b is the Boltzmann constant, T is the absolute temperature, m* is the effective mass of the carrier, these parameters can be obtained by consulting the data; C is the elastic modulus along the crystal axis; d is the deformation potential of electrons or holes, and d is d when describing the intrinsic electron mobility. e , when describing the intrinsic hole mobility, d is d h The electron and hole deformation potentials are measured through the above experiments. When calculating the intrinsic carrier mobility of electrons or holes, it is necessary to substitute the effective mass and deformation potential of the corresponding type of carrier into the above formula.

[0109] The above description is only used to help understand the method and core essence of the present invention, but the scope of protection of the present invention is not limited thereto. For those skilled in the art, equivalent replacements or modifications based on the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention should be included in the scope of protection of the present invention. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for measuring the intrinsic carrier mobility of a semiconductor material, characterized in that: The steps include: S1. Select semiconductor materials as samples, build a measurement system for the intrinsic carrier mobility of semiconductor materials, and use femtosecond laser pulses to excite the semiconductor materials; S2. Detecting the Brillouin oscillation signal using a measurement system: Using an optical delay line to continuously change the relative time delay between the probe light and the pump light, and obtaining the probe light intensity with and without the pump light, the transient reflection dynamics spectrum of the semiconductor material is measured; and the Brillouin oscillation signal is extracted based on the transient reflection dynamics spectrum. S3. Based on the Brillouin oscillation signal, obtain the elastic modulus of the semiconductor material, the relative defect state density of the semiconductor material, and calculate the electron deformation potential and hole deformation potential; The electron deformation potential and hole deformation potential are calculated as follows: Select the excitation photon density N The same excitation photon energies are and The excitation light excites the same sample, When the measured amplitude ratio of the two Brillouin oscillation signals is , and the deformation potential pressure is obtained and the thermoelastic pressure under two excitation conditions and The expression is: Under the same excitation conditions, the excited defect state densities are n and For two single crystal samples with different defect state densities, the following relationship is obtained: in, and is the thermoelastic pressure of two semiconductor materials under the same excitation conditions, and is the deformation potential pressure of the two semiconductor materials; is the known relative defect state density coefficient; and are the known bulk elastic modulus and linear expansion coefficient, is the known heat capacity of the material; represents the excitation photon energy, N represents the excitation photon density, 、 N are experimental parameters; n is the electron defect state density; represents the energy difference between the defect state and the bottom of the conduction band; The electron deformation potential is obtained in turn , hole deformation potential , electron defect state density n ; S4. Based on the electron deformation potential, hole deformation potential and elastic modulus of the semiconductor material, the intrinsic carrier mobility of the semiconductor material is calculated.

2. The method according to claim 1, characterized in that The S1 is specifically as follows: The 800 nm femtosecond pulse light with a repetition rate of 1 kHz emitted from the femtosecond laser is divided into a detection light path and a pump light path through a beam splitter; After entering the OPA system, the pump light is modulated into high-energy monochromatic pulse light with a repetition rate of 500 Hz and a wavelength of 400 nm or any wavelength in the range of 460 to 700 nm. After reflection and focusing, the modulated pump light converges on the sample. The probe light enters the optical delay line (ODL) to control the time delay between the pump light and the probe light. After emitting from the optical delay line (ODL), the probe light is focused onto the sapphire crystal (Sapphire) to generate supercontinuum white light. The supercontinuum white light is then divided into a reference light path and a probe light path by a beam splitter. After being reflected and focused, the reference light finally enters the spectrometer; The probe light is focused on the sample and spatially overlaps with the pump light; The detection light carrying the sample information reflected by the sample surface is reflected and focused, and finally enters the spectrometer.

3. The method according to claim 1, characterized in that The S2 is specifically as follows: The repetition rate of the pump light was modulated to 500 Hz, and the repetition rate of the probe light was maintained at 1 kHz, with a cycle of 2 ms. During the first 1 ms of a cycle at time 0, the intensity of the probe light with the pump light was obtained because the probe light and pump light overlapped in time. During the second 1 ms of the same cycle, the intensity of the probe light without the pump light was obtained. The transient reflectivity change amplitude of the semiconductor material surface at time 0 is calculated; Based on the 0 moment, the optical path of the detection light is extended to detect the pump light effect. x ps The amplitude of transient reflectivity change after the test is obtained. Similarly, by using an optical delay line to continuously change the relative time delay between the probe light and the pump light, the complete transient reflectivity dynamic spectrum of the semiconductor material is tested. The carrier signal background is obtained by a smoothing function based on the adjacent averaging method, and the Brillouin oscillation signal is obtained by subtracting the carrier signal background from the raw data of the transient reflection dynamics spectrum.

4. The method according to claim 3, characterized in that The S4 is specifically as follows: The intrinsic carrier mobility of semiconductor materials is calculated as follows: in, is the intrinsic carrier mobility; is the reduced Planck constant, e is the elementary charge, k b is the Boltzmann constant, T is the absolute temperature, is the effective mass of the electron or hole; is the elastic modulus along the crystal axis; d is the deformation potential of electrons or holes, and is used to describe the intrinsic electron mobility. d for , when describing the intrinsic hole mobility d for .

5. The method according to claim 3, characterized in that The elastic pressure of the semiconductor material along the transmission direction is calculated based on the electron deformation potential and the hole deformation potential, as follows: The elastic pressure generated by the photoexcited semiconductor material is proportional to the initial amplitude of the Brillouin oscillation signal in the time domain. Including thermoelastic pressure and deformation potential pressure ;Right now in, represents the electron deformation potential, represents the hole deformation potential.

6. The method according to claim 4, characterized in that The elastic modulus of the semiconductor material is obtained in S3, specifically: The time-domain Brillouin scattering technique is used to measure semiconductor materials, obtain Brillouin oscillation signals under different crystal orientation conditions, extract the oscillation frequency, and give the elastic modulus of the corresponding material; elastic modulus Expressed as: in, For the experimental detection wavelength, f is the Brillouin oscillation frequency, n is the refractive index of the material at the corresponding detection wavelength, is the material density.

7. The method according to any one of claims 4 to 6, characterized in that: The relative defect state density characterization of the semiconductor material is obtained in S3, specifically: Time-domain Brillouin scattering technology is used to characterize the Brillouin oscillation signals of samples with different defect state densities. Based on the fact that the Brillouin oscillation relaxation rate is proportional to the material defect state density, the ratio of the material's defect state density can be inferred from the ratio of its Brillouin oscillation relaxation rates.

8. The method according to any one of claims 4 to 6, characterized in that: The energy difference between the defect state and the bottom of the conduction band , specifically: Transient absorption spectroscopy technology is used to test the transient absorption spectrum signals of various semiconductor single crystal materials, determine the bleaching peaks corresponding to the defect state energy level and the conduction band bottom, and calculate the energy difference between the defect state energy level and the conduction band bottom.

Images