Carrier-trap resolution measurement system and method based on axial magnetic field modulation

Abstract

This invention relates to the field of semiconductor electrical measurement technology, and particularly to a carrier-trap resolution measurement system and method based on axial magnetic field modulation. The system includes a light source and intensity modulation unit, an optical microscope / confocal unit, an axial magnetic field modulation device, a control unit, an electrical measurement unit, and a data acquisition and digital phase-locked loop unit. The axial magnetic field modulation device employs a symmetrical permanent magnet ring and a vertical light-transmitting barrel structure, combined with a soft magnetic permeability modulation wheel, to form a stable alternating axial magnetic field perpendicular to the sample, with the optical path coaxially incident vertically. The method includes sample clamping and alignment, parameter initialization, synchronous acquisition of longitudinal resistance signals and transverse Hall signals, spectrum confirmation, digital phase-locked loop analysis, and multi-external parameter scanning output. The advantages are: reducing mechanical vibration and optical path interference by rotating the soft magnetic permeability modulation wheel, thus improving signal stability; and achieving weak Hall signal extraction by combining phase-locked loop detection, efficiently separating carrier and trap responses.

Description

Technical Field

[0001] This invention relates to the field of semiconductor electrical measurement technology, and in particular to a carrier-trap resolution measurement system and method based on axial magnetic field modulation. Background Technology

[0002] Photo-Hall measurement involves simultaneously measuring the conductivity and Hall response of a sample under illumination. Under different light intensities (or different spectra / temperatures), by measuring the longitudinal resistance / conductivity and the transverse Hall signal (or Hall coefficient), illumination-dependent transport parameters such as photogenerated carrier concentration and mobility can be extracted. Furthermore, within a carrier-resolved or trap-resolved framework, the "conductivity-Hall quantity" curve varying with light intensity can be used to invert the mobility differences between majority and minority carriers, trap filling behavior, etc. This type of experiment places more stringent requirements on magnetic field and electrical detection than traditional dark-state Hall effects: on the one hand, many photovoltaic / novel semiconductor thin films have extremely high resistance or very low mobility in the dark or with low injection, resulting in extremely weak Hall signals and significant noise; on the other hand, under illumination, factors such as light source fluctuations, thermal drift, contact potential drift, and longitudinal and transverse aliasing are also superimposed. Leak to Background information is needed. Existing research has clearly indicated that "noisy Hall signals" can occur in thin films with high resistance or low mobility. Therefore, AC-field Hall technology combined with Fourier analysis and phase-locked detection is crucial for obtaining "clean Hall signals." Furthermore, since optical Hall signals typically require recording long time series at each light intensity point and performing frequency domain / phase-sensitive processing, high demands are placed on the system's mechanical stability and optical-electrical-magnetic synchronization capabilities.

[0003] In existing optical Hall effect measurement techniques, a rotating parallel dipole line (PDL) magnet optical Hall effect measurement system is disclosed: the sample is placed between a pair of PDL permanent magnets and the longitudinal and transverse signals are measured under illumination; the PDL consists of a pair of diameter-magnetized cylindrical permanent magnets and adopts a "master-slave" coupled rotation mode. The master magnet is driven by a motor and the slave magnet follows in the opposite direction, thereby generating a unidirectional, near-single-harmonic alternating magnetic field in the central region of the sample as a modulation source for phase-locked reference; in the experiment, the master magnet is usually rotated by a stepper motor at about 1~2 rpm to generate an alternating magnetic field. The magnetic field amplitude at a typical sample is about 0.70T (the gap between the magnets is about 10mm), and a Hall sensor is used to monitor the oscillating magnetic field and record the magnetic field and its relationship with the sample. The time series (each light intensity point can be sampled for 15~30 minutes) was then confirmed by Fourier spectroscopy. An effective component exists at the same frequency as the magnetic field. Software phase-sensitive phase-locked loop is then used to extract the Hall in-phase component and suppress out-of-phase spurious signals caused by Faraday induction, etc. Optically, the light intensity is usually modulated by an electrodynamic neutral density filter (or a continuous neutral density filter). After beam expansion and deflection, the beam illuminates the sample region located between the PDL magnets. In a further carrier-trap-resolved photo-Hall (CTRPH) system, this PDL rotating magnet structure can also be combined with a cryogenic isothermal platform. The sample is also located between two rotating PDL magnets and subjected to a vertical oscillating magnetic field (peak amplitude of about 0.5T) to achieve temperature-light intensity joint scanning.

[0004] While the above-mentioned rotating PDL optical Hall system can achieve AC magnetic field and phase-locked extraction, it has several shortcomings in the proposed "microscopic confocal optical-electric synchronization" scenario: (1) Rotating components are permanent magnets or large mass components: Low-frequency long-term sampling requires mechanical stability. Rotating large mass magnets are more likely to introduce vibration, micro-displacement and noise coupling, which is not conducive to the stable alignment and repeatability of high-magnification microscopy / confocal platform. (2) The optical path is not naturally "vertically connected": Existing optical Hall devices usually organize the optical path in the way that "the sample is located between two magnets + the beam is deflected to irradiate the sample area"; if it is to be upgraded to "the objective lens is vertically incident / collected + confocal + scanning", it is necessary to solve additional problems such as magnet obstruction, working distance, light passage and scattering control. (3) The direction of alternating magnetic field is limited in matching with the microscopic platform: Confocal microscopy usually requires an optical axis channel perpendicular to the sample plane and a stable sample stage; however, the direction of the magnetic field and the structural layout of the existing PDL do not take "axial (perpendicular to sample) magnetic field + vertical light aperture" as an inherent constraint. (4) Processing of spurious signals depends on frequency domain / phase-sensitive separation: Existing systems themselves emphasize the need to use phase-sensitive phase-locked loops to extract in-phase Hall signals and reject out-of-phase spurious signals (such as Faraday induction); therefore, if spurious signals and mechanical disturbances can be reduced at the structural level, the availability and scalability of the system will be significantly improved. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a carrier-trap resolution measurement system and method based on axial magnetic field modulation.

[0006] The primary objective of this invention is to provide a carrier-trap resolution measurement system based on axial magnetic field modulation, comprising a light source and light intensity modulation unit, an optical microscopy / confocal unit, an axial magnetic field modulation device, a control unit, an electrical measurement unit, and a data acquisition and digital phase-locked loop unit; A light source and light intensity modulation unit, and an optical microscopy / confocal unit are sequentially arranged along the optical path. The light beam is perpendicularly incident on the sample surface through the light transmission channel of the axial magnetic field modulation device. The axial magnetic field modulation device includes an upper permanent magnet ring, a lower permanent magnet ring, an air gap, a sample holder, a vertical light-transmitting barrel, a soft magnetic permeability modulation wheel, a motor shaft, and a synchronous belt; wherein, the soft magnetic permeability modulation wheel is a ring-shaped disk structure, including an outer ring modulation structure that realizes equivalent magnetic permeability sinusoidal change and a central light-transmitting hole; The control unit is used to drive the soft magnetic permeation modulation wheel to rotate and output a phase speed reference signal to the data acquisition and digital phase-locked unit; The electrical measurement unit is connected to the sample electrode and is used to acquire the electrical signal of the sample and output it to the data acquisition and digital phase-locked unit. The data acquisition and digital phase-locked loop unit is used to extract the same-frequency optical Hall component based on the phase rotation speed reference signal, and to analyze and separate the carrier and trap response components.

[0007] Preferably, the upper permanent magnet ring and the lower permanent magnet ring are arranged symmetrically in the vertical direction, and the N poles of both rings face the air gap side; the upper permanent magnet ring and the lower permanent magnet ring are axially magnetized neodymium iron boron magnetic rings; The vertical light-transmitting barrel passes through the central through-hole of the upper permanent magnet ring and the lower permanent magnet ring; the axis of the vertical light-transmitting barrel coincides with the normal direction of the sample, forming a coaxial vertical light-transmitting channel.

[0008] Preferably, the motor is located outside the air gap and does not intrude into the light-transmitting area; the motor shaft drives the soft magnetic modulation wheel to rotate via a synchronous belt.

[0009] Preferably, the modulation structure for achieving an equivalent sinusoidal change in magnetic permeability of the outer ring of the soft magnetic permeability modulation wheel is one of a continuously widened groove structure, a continuously varying effective thickness structure, or a continuously varying outer contour undulation structure.

[0010] Preferably, the continuously widened groove structure is symmetrical petal-shaped, with the groove width changing smoothly and continuously along the circumference, without abrupt sharp edges; The soft magnetic permeation modulation wheel is made of a thin sheet or stack of soft magnetic material, and the material is one of low carbon steel, electrical silicon steel, pure iron or permalloy.

[0011] Preferably, the phase speed reference signal output by the control unit is directly generated by the internal timing logic of the control unit, or acquired by one of the following corner sensing components: encoder, photoelectric gate, reflective marker, and magnetic encoder ring.

[0012] Preferably, the phase speed reference signal adopts a dual-reference redundant synchronization method with two reference signals.

[0013] The second objective of this invention is to provide a carrier-trap resolution measurement method based on axial magnetic field modulation, implemented using the aforementioned carrier-trap resolution measurement system based on axial magnetic field modulation, comprising the following steps: S1: Fix the test sample onto the sample holder and complete the electrode lead connection; align the optical axis of the system; S2: By setting the magnetic field modulation frequency and the rotational angular velocity of the soft magnetic permeable modulation wheel through the control unit, the motor shaft and synchronous belt are started to drive the soft magnetic permeable modulation wheel to rotate at the set angular velocity; at the same time, the phase speed reference signal output mode is configured to obtain the actual rotational phase of the soft magnetic permeable modulation wheel; S3: The electrical measurement unit synchronously acquires the longitudinal resistance signal of the sample. With transverse Hall signal The acquired signal and the phase speed reference signal are synchronously transmitted to the data acquisition and digital phase-locked unit. S4: Spectrum Confirmation and Signal Preprocessing: Data Acquisition and Digital Phase-Locked Unit (PLL) process the acquired transverse Hall signal. Spectral analysis was performed to confirm the existence of an effective co-frequency component at the reference frequency of the magnetic field modulation, and out-of-phase pseudo-signals were identified and marked. S5: Based on phase-speed reference signal pair Digital lock-in amplification is performed to extract the in-phase Hall component that is in the same frequency as the magnetic field modulation, thereby suppressing out-of-phase spurious signals. S6: Repeat steps S3-S5 under different light intensities and temperatures, collect multiple sets of measurement data and analyze them, output the optical Hall parameters and their curves showing how they change with external parameters, and complete the carrier-trap resolved optical Hall measurement.

[0014] Preferably, the magnetic field modulation frequency is in the range of 0.001~1000Hz.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) Vertical light-passing structure is inherently compatible with microscopic confocalization: The vertical light-passing barrel connects the magnetic ring and the air gap, and the objective lens is vertically incident / collected without being blocked by the magnet; while existing schemes usually require beam expansion and deflection to hit the sample area between the magnets.

[0016] (2) The permanent magnet is fixed and does not rotate, and the vibration source is significantly reduced: the rotating part is supported by a thin soft magnetic wheel, which has small mass and small inertia; the drive is external, which is more friendly to the microscopic platform.

[0017] (3) The direction of the magnetic field is defined as the axial magnetic field strength according to the requirements of the microscopic platform. It is better suited for flat film, vertical optical axis, and confocal scanning.

[0018] (4) Adjustable waveform engineering: The continuous sinusoidal magnetic permeation structure actively suppresses harmonics, improves the dominance of the fundamental wave, and reduces the complexity of phase-locked loop solution.

[0019] (5) More stable reference phase: The encoder phase output can be used as a phase-locked reference, reducing the additional coupling and error sources caused by using a magnetic field probe as a reference; at the same time, phase-sensitive separation of in-phase / out-of-phase can still be used to suppress induced pseudo signals (existing schemes have proven that this strategy is necessary). Attached Figure Description

[0020] Figure 1 This is a block diagram of a carrier-trap resolved optical Hall measurement system provided according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the axial magnetic field modulation device provided in an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the assembly of a soft magnetic permeation modulation wheel and a motor shaft according to an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the planar structure of the soft magnetic permeability modulation wheel according to an embodiment of the present invention.

[0024] Figure 5 This is a flowchart of the carrier-trap resolved optical Hall measurement method provided in an embodiment of the present invention.

[0025] Figure label: 1. Install a permanent magnet ring; 2. Lower permanent magnet ring; 3. Air gap; 4. Sample tray; 5. Sample; 6. Vertical light-transmitting barrel; 7. Soft magnetic permeability modulation wheel; 701. Modulation wheel outer diameter; 702. Continuously widening groove structure; 703. Central light-transmitting hole; 8. Motor shaft; 9. Synchronous belt. Detailed Implementation

[0026] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0028] See Figure 1 This invention provides a carrier-trap resolution measurement system based on axial magnetic field modulation, comprising: a light source and light intensity modulation unit, an optical microscopy / confocal unit, an axial magnetic field modulation device, a control unit, an electrical measurement unit, and a data acquisition and digital phase-locked loop unit; the units form three collaborative links, namely an optical excitation link, a magnetic field modulation and synchronization control link, and an electrical measurement and data processing link, which converge and work together at the sample to achieve synchronous acquisition of optical excitation, axial magnetic field modulation, and electrical signals of the sample; The beam output end of the light source and intensity modulation unit is optically coupled to the input end of the optical microscopy / confocal unit. The output end of the optical microscopy / confocal unit is optically coupled to the sample position of the axial magnetic field modulation device. The beam is perpendicularly incident on the sample surface through the light transmission channel in the axial magnetic field modulation device, providing the sample with a controllable excitation light signal. The axial magnetic field modulation device is used to provide a modulated axial magnetic field for the sample. It integrates a sample mounting structure and a light transmission channel to meet the working requirements of optical excitation and electrical measurement. The speed control output of the control unit is electrically connected to the drive mechanism in the axial magnetic field modulation device, controlling the drive mechanism to drive the magnetic modulation wheel to rotate; the phase reference output of the control unit is electrically connected to the data acquisition and digital phase-locked unit, providing a synchronous reference signal for magnetic field modulation. The sample's electrodes are led out through the sample holder and electrically connected to the input terminal of the electrical measurement unit; the measurement data output terminal of the electrical measurement unit is electrically connected to the signal input terminal of the data acquisition and digital phase-locked loop unit. The measurement data output by the electrical measurement unit and the phase speed reference signal output by the control unit are synchronously input to the data acquisition and digital phase-locked unit; The data acquisition and digital phase-locked unit is based on digital phase-locked amplification technology. It extracts the effective signal component with the same frequency as the magnetic field modulation, suppresses out-of-phase pseudo signals, further analyzes and separates the charge carrier and trap response components, and finally outputs the processing results, forming a complete closed-loop path from the acquisition of the original electrical signal to the output of the analysis results. The digital phase-locked unit can be implemented by hardware phase-locked amplifier or software phase-locked, and the two can be interchanged or used together. In some embodiments, the phase speed reference signal can be directly generated by the control unit through internal timing logic, or the angle sensing component can be configured to collect the actual angle phase of the modulation wheel to achieve redundant synchronization. The angle sensing component can be any one of an encoder, photoelectric gate, reflective mark, or magnetic encoder ring, and can also be configured with two reference signals to form a dual-reference redundant synchronization mode.

[0029] See Figures 2-4 The axial magnetic field modulation device mainly includes: upper permanent magnet ring 1, lower permanent magnet ring 2, air gap 3, sample holder 4, vertical light transmission barrel 6, soft magnetic permeable modulation wheel 7, motor shaft 8 and synchronous belt 9. The upper permanent magnet ring 1 and the lower permanent magnet ring 2 are axially magnetized neodymium iron boron (NdFeB) magnetic rings, which are symmetrically arranged in the vertical direction (phase difference 180°) to further suppress even harmonics and assembly eccentricity. The N poles of the upper permanent magnet ring 1 and the lower permanent magnet ring 2 are both facing the air gap 3 side, forming a uniform air gap between the upper permanent magnet ring 1 and the lower permanent magnet ring 2. The sample holder 4 is located in the central region of the air gap 3. The sample 5 is fixedly installed on the sample holder 4 and is located in the region of uniform magnetic field distribution. The electrode of the sample 5 is led out through the sample holder 4 and electrically connected to the electrical measurement unit. The vertical light-transmitting barrel 6 passes through the central through-hole of the upper permanent magnet ring 1 and the lower permanent magnet ring 2. Its axis coincides with the normal direction of the sample 5, providing a coaxial channel for the incident light beam so that the light beam can be incident perpendicularly onto the surface of the sample 5. The vertical light-transmitting barrel 6 is made of non-magnetic material and the inner wall is treated with an anti-light treatment to avoid scattering and magnetic interference. The soft magnetic permeability modulation wheel 7 is disposed in the air gap 3 region, located on one side of the sample holder 4. A light-transmitting hole coaxial with the vertical light-transmitting barrel 6 is opened in its center. The outer ring has a continuously widened groove structure, continuously varying effective thickness, or continuously varying outer contour undulation, which can realize an equivalent magnetic permeability sine structure. The soft magnetic permeability modulation wheel 7 is fixed on the annular turntable and remains coaxial with the vertical light-transmitting barrel 6. It is connected to the motor shaft 8 through a synchronous belt 9. In some embodiments, the soft magnetic permeability modulation wheel 7 is made of soft magnetic material sheets or stacks, and the material is low carbon steel, electrical silicon steel, pure iron, permalloy, etc. The motor shaft 8 is electrically connected to the control unit and is driven to rotate by the speed control signal output by the control unit, which in turn drives the soft magnetic guide modulated wheel 7 to rotate around the axis at an angular velocity ω. The motor is located outside the air gap 3 and drives the annular turntable to rotate via the synchronous belt 9, preventing the driving components from intruding into the light transmission area. In some embodiments, the driving method adopts synchronous belt, gear transmission or magnetic coupling transmission, so that the motor is away from the light path and magnetic field area.

[0030] In some embodiments, the soft magnetic permeability modulation wheel 7 is an annular disk structure, made entirely of soft magnetic material, and mainly includes a modulation wheel outer diameter 701, a continuously widening groove structure 702, and a central light-transmitting hole 703 (see...). Figure 4 The continuously widened groove structure 702 is symmetrically petal-shaped, with the groove width continuously and smoothly changing along the circumference without abrupt sharp edges. The outer diameter 701 of the modulation wheel matches the air gap size of the axial magnetic field modulation device, ensuring that the soft magnetic permeable modulation wheel 7 is always within the effective magnetic circuit coupling area during rotation. The inner ring of the soft magnetic permeable modulation wheel 7 has a central light-passing hole 703, which is coaxially set with the vertical light-passing barrel 6, allowing the excitation beam to pass through the modulation wheel and be incident vertically on the surface of the sample 5, avoiding the light path being blocked by the soft magnetic permeable modulation wheel 7. The outer ring of the soft magnetic permeable modulation wheel 7 is a continuously widened groove structure 702, with the groove shape being symmetrically distributed in a petal shape, and the groove width continuously and smoothly changing along the circumference without abrupt sharp edges. When the soft magnetic permeability modulation wheel 7 moves at an angular velocity When rotating around the optical axis, the continuously widening groove structure 702 makes the effective magnetic permeability of the magnetic circuit change with the rotation angle. Continuously changing, effective magnetic permeability of the magnetic circuit The following relationship is approximately satisfied: ; in, It has static magnetic permeability. For modulation depth, Extreme logarithm (preferred) =1 to obtain the cleanest fundamental component). It is the phase constant; The periodic variation in magnetic permeability causes a periodic change in the magnetic reluctance of the air gap magnetic circuit with the rotation angle, which in turn causes the axial magnetic field strength passing through sample 5 to form an alternating component dominated by the fundamental wave. The expression is:

[0031] in, This represents the static bias magnetic field strength. The amplitude of the magnetic field modulation. To modulate the wheel angular velocity, The phase constant is denoted by . This near-single-harmonic alternating magnetic field provides a stable modulation source for subsequent phase-locked loop measurements, effectively suppressing high-order harmonic noise and improving the extraction accuracy of carrier-trap response components.

[0032] During operation, the upper permanent magnet ring 1 and the lower permanent magnet ring 2 together form a uniform static axial magnetic field within the air gap 3, which acts perpendicularly on the surface of sample 5. The control unit outputs a speed control signal to drive the motor shaft 8 to rotate, which in turn drives the soft magnetic permeability modulation wheel 7 to rotate synchronously via the synchronous belt 9. During the rotation of the soft magnetic permeability modulation wheel 7, the continuously changing groove structure of its outer ring periodically changes the effective cross-sectional area of ​​the magnetic circuit, causing the magnetic permeability of the magnetic circuit to change periodically with the rotation angle. This, in turn, generates near-single harmonic alternating modulation of the axial magnetic field strength passing through sample 5, forming a stable AC modulation magnetic field, providing a synchronous reference source for subsequent phase-locked loop measurements. Simultaneously, the incident light beam is incident along the axis of the vertical light-transmitting barrel 6, passes through the central light-transmitting hole of the soft magnetic permeability modulation wheel 7, and vertically illuminates the surface of sample 5, providing controllable photoexcitation conditions for the sample. Under the combined action of the alternating axial modulation magnetic field and photoexcitation, sample 5 generates an electrical signal, which is led out through the electrodes of sample holder 4 and input to the electrical measurement unit to complete the carrier-trap resolved optical Hall measurement process.

[0033] Based on the above measurement system, the present invention also provides a carrier-trap resolution measurement method based on axial magnetic field modulation, the flowchart of which can be found in the figure. Figure 5 Specifically, it includes the following steps: S1. Sample clamping and system alignment: Fix the sample to be tested on the sample holder and complete the electrode lead connection; adjust the coaxiality of the vertical light-transmitting barrel, the soft magnetic induction modulation wheel and the optical microscope / confocal unit so that the excitation beam passes through the central light-transmitting hole and is vertically incident on the sample surface, and complete the optical axis alignment and electrical path continuity check.

[0034] S2. Parameter Setting and System Initialization: Set the magnetic field modulation frequency (preferably in the mHz range to low Hz, i.e., 0.001~1000Hz) and the rotational angular velocity of the soft magnetic permeable modulation wheel through the control unit. Start the motor shaft and synchronous belt drive mechanism to drive the soft magnetic permeable modulation wheel at the set angular velocity. Rotation; simultaneously configured with a phase speed reference signal output mode, which can be directly generated by the timing logic inside the control unit, or synchronously output by acquiring the actual rotational phase of the modulation wheel through a rotation angle sensing component (encoder, photoelectric gate, reflective mark, magnetic encoder ring or dual reference redundancy method).

[0035] S3. Synchronous Signal Acquisition: Under the combined action of an alternating axially modulated magnetic field and optical excitation, the electrical measurement unit synchronously acquires the longitudinal resistance signal of the sample. With transverse Hall signal The aforementioned signals, along with the phase and speed reference signals output by the control unit, are synchronously transmitted to the data acquisition and digital phase-locked loop unit.

[0036] S4. Spectrum Confirmation and Signal Preprocessing: Data Acquisition and Digital Phase-Locked Unit (PLL) process the acquired transverse Hall signal. Spectral analysis was performed to confirm the existence of an effective co-frequency component at the reference frequency of the magnetic field modulation. Out-of-phase pseudo-signals were identified and marked to provide a reference for subsequent phase-locked loop processing.

[0037] S5. Digital Phase-Locked Loop and Component Analysis: Based on the phase and speed reference signal output by the control unit, for... Digital lock-in amplification is performed to extract the in-phase Hall component that is in sync with the magnetic field modulation, thus suppressing out-of-phase spurious signals; combined with the longitudinal resistance signal... The carrier and trap response components were analyzed and separated.

[0038] S6. External parameter scanning and result output: Under different external parameter conditions such as light intensity and temperature, repeat steps S3-S5, collect multiple sets of measurement data and perform statistical analysis, and finally output the optical Hall parameters and their regular curves as a function of external parameters, thus completing one carrier-trap resolved optical Hall measurement.

[0039] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0040] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A carrier-trap resolution measurement system based on axial magnetic field modulation, characterized by: It includes a light source and light intensity modulation unit, an optical microscopy / confocal unit, an axial magnetic field modulation device, a control unit, an electrical measurement unit, and a data acquisition and digital phase-locked loop unit; A light source and light intensity modulation unit, and an optical microscopy / confocal unit are sequentially arranged along the optical path. The light beam is perpendicularly incident on the sample surface through the light transmission channel of the axial magnetic field modulation device. The axial magnetic field modulation device includes an upper permanent magnet ring, a lower permanent magnet ring, an air gap, a sample holder, a vertical light-transmitting barrel, a soft magnetic permeability modulation wheel, a motor shaft, and a synchronous belt; wherein, the soft magnetic permeability modulation wheel is a ring-shaped disk structure, including an outer ring modulation structure that realizes equivalent magnetic permeability sinusoidal change and a central light-transmitting hole; The control unit is used to drive the soft magnetic permeation modulation wheel to rotate and output a phase speed reference signal to the data acquisition and digital phase-locked unit; The electrical measurement unit is connected to the sample electrode and is used to acquire the electrical signal of the sample and output it to the data acquisition and digital phase-locked unit. The data acquisition and digital phase-locked loop unit is used to extract the same-frequency optical Hall component based on the phase rotation speed reference signal, and to analyze and separate the carrier and trap response components.

2. The carrier-trap resolution measurement system based on axial magnetic field modulation according to claim 1, characterized in that: The upper permanent magnet ring and the lower permanent magnet ring are arranged symmetrically in the vertical direction, and the N poles of both rings face the air gap side; the upper permanent magnet ring and the lower permanent magnet ring are axially magnetized neodymium iron boron magnetic rings; The vertical light-transmitting barrel passes through the central through-hole of the upper permanent magnet ring and the lower permanent magnet ring; the axis of the vertical light-transmitting barrel coincides with the normal direction of the sample, forming a coaxial vertical light-transmitting channel.

3. The carrier-trap resolution measurement system based on axial magnetic field modulation of claim 1, wherein: The motor is located outside the air gap and does not intrude into the light-transmitting area; the motor shaft drives the soft magnetic modulation wheel to rotate via a synchronous belt.

4. The carrier-trap resolution measurement system based on axial magnetic field modulation of claim 1, wherein: The modulation structure for achieving an equivalent sinusoidal change in magnetic permeability on the outer ring of the soft magnetic permeability modulation wheel is one of the following: a continuously widened groove structure, a continuously varying effective thickness structure, or a continuously varying outer contour undulation structure.

5. The carrier-trap resolution measurement system based on axial magnetic field modulation according to claim 4, characterized in that: The continuously widened groove structure is symmetrical petal-shaped, with the groove width changing smoothly and continuously along the circumference, without abrupt sharp angles. The soft magnetic permeation modulation wheel is made of a thin sheet or stack of soft magnetic material, and the material is one of low carbon steel, electrical silicon steel, pure iron or permalloy.

6. The carrier-trap resolution measurement system based on axial magnetic field modulation of claim 1, wherein: The phase rotation speed reference signal output by the control unit is directly generated by the internal timing logic of the control unit, or acquired by one of the following corner sensing components: encoder, photoelectric gate, reflective marker, and magnetic encoder ring.

7. The carrier-trap resolution measurement system based on axial magnetic field modulation according to claim 6, characterized in that: The phase rotation speed reference signal adopts a dual-reference redundant synchronization method with two reference signals.

8. A carrier-trap resolution measurement method based on axial magnetic field modulation, implemented based on the carrier-trap resolution measurement system based on axial magnetic field modulation in claim 1, characterized in that: Includes the following steps: S1: Fix the test sample onto the sample holder and complete the electrode lead connection; align the optical axis of the system. S2: By setting the magnetic field modulation frequency and the rotational angular velocity of the soft magnetic permeable modulation wheel through the control unit, the motor shaft and synchronous belt are started to drive the soft magnetic permeable modulation wheel to rotate at the set angular velocity; at the same time, the phase speed reference signal output mode is configured to obtain the actual rotational phase of the soft magnetic permeable modulation wheel; S3: the electrical measuring unit synchronously collects the longitudinal resistance signal of the sample with the transverse Hall signal and synchronously transmits the collected signal with the phase speed reference signal to the data collection and digital phase-locked unit; S4: Spectrum confirmation and signal preprocessing: the transverse Hall signal collected by the data acquisition and digital phase-locked unit Spectrum analysis is performed to confirm the existence of effective co-frequency components at the reference frequency of magnetic field modulation, identify and mark out-of-phase false signals; S5: based on the phase speed reference signal to Carry out digital phase lock amplification processing, extract the same phase light Hall component with the same frequency as the magnetic field modulation, and suppress the different phase false signal; S6: Repeat steps S3-S5 under different light intensities and temperatures, collect multiple sets of measurement data and analyze them, output the optical Hall parameters and their curves showing how they change with external parameters, and complete the carrier-trap resolved optical Hall measurement.

9. The carrier-trap resolution measurement method based on axial magnetic field modulation according to claim 8, characterized in that: The magnetic field modulation frequency is in the range of 0.001~1000Hz.

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