Method for detecting photoconductivity and absorption coefficient of n-type semiconductor thin film

Abstract

The application discloses a kind of n-type semiconductor thin film photoconductivity and absorption coefficient detection method, belong to optical detection technical field, method includes: IF displacement difference acquisition module measures the spot position information of left-handed and right-handed circularly polarized light incident to n-type semiconductor thin film, and obtains the IF displacement difference of incident wavelength-left and right circularly polarized light of n-type semiconductor thin film;Transmission spectrum acquisition module obtains the transmission spectrum data of n-type semiconductor thin film under left-handed and right-handed circularly polarized light;Inversion calculation module is into the evaluation function of n-type semiconductor thin film dielectric function by the IF displacement difference and transmission spectrum data, carries out inversion calculation, obtains the complex refractive index of n-type semiconductor thin film;Photoconductivity and absorption coefficient calculation module obtains the photoconductivity and absorption coefficient of n-type semiconductor thin film according to the complex refractive index of n-type semiconductor thin film.Effect: it can accurately measure the photoconductivity and absorption coefficient of n-type semiconductor thin film.

Description

Technical Field

[0001] This invention relates to the field of optical detection technology, and in particular to a method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film. Background Technology

[0002] n-type semiconductor thin films are core functional layers in display touchscreens, photovoltaic cells, and advanced wafer fabrication. Measuring the photoconductivity and absorption coefficient of n-type semiconductor thin films aims to deeply understand the photoelectric response mechanism and carrier transport characteristics within the material. Photoconductivity, as a complex parameter, has a real part directly related to the material's conductance contribution under an optical field, while its imaginary part reflects polarization relaxation and energy storage characteristics. Together, they reveal the generation, recombination, and migration behavior of photogenerated carriers. By accurately measuring photoconductivity, researchers can quantify the impact of doping concentration, lattice defects, and interface states on electrical performance, thereby assessing the material's suitability for high-frequency optoelectronic applications. Simultaneously, measuring the absorption coefficient aims to quantify the material's ability to capture incident photons, directly determining the spectral response range and quantum efficiency of optoelectronic devices. In n-type semiconductors, the absorption edge is closely related to the bandgap energy. By measuring the change in absorption coefficient with wavelength, the optical bandgap of the material can be accurately calculated, and physical effects such as the Burstein-Moss shift can be analyzed, providing crucial data support for bandgap engineering design.

[0003] From the perspective of technological application and device development, the precise characterization of these two parameters has profound guiding significance. They are the bridge connecting the microstructure of materials and the performance of macroscopic devices, and are crucial for optimizing devices such as photodetectors, solar cells, and field-effect transistors. The absorption coefficient directly determines the thickness design of the light absorption layer and the light energy utilization rate, while photoconductivity affects the response speed and gain characteristics of the device. In the screening and process optimization of new semiconductor materials, by jointly analyzing photoconductivity and absorption coefficient, the crystal quality and uniformity of thin films can be effectively evaluated, and defect mechanisms such as non-radiative recombination centers can be identified. This not only helps to improve the photoelectric conversion efficiency of devices, but also provides accurate input parameters for numerical simulation of devices, thereby accelerating the transformation process from basic laboratory research to industrial mass production and promoting the iterative upgrading of high-performance optoelectronic technologies.

[0004] Therefore, there is an urgent need in the field for a measurement method that can accurately measure the photoconductivity and absorption coefficient of n-type semiconductor thin films. Summary of the Invention

[0005] This invention provides a method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film, which can accurately measure the photoconductivity and absorption coefficient of an n-type semiconductor thin film.

[0006] To achieve the above objectives, the present invention provides a method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film, the key of which includes the following steps:

[0007] Step 1: Construct a photoconductivity and absorption coefficient detection system for n-type semiconductor thin films. This photoconductivity and absorption coefficient detection system is equipped with an IF shift difference acquisition module and a transmission spectrum acquisition module. The IF shift difference acquisition module and the transmission spectrum acquisition module are connected to the same inversion calculation module, which is connected to a photoconductivity and absorption coefficient calculation module.

[0008] Step 2a: The IF displacement difference acquisition module uses the IF displacement measurement device to measure the spot position information of left-handed and right-handed circularly polarized light incident on the n-type semiconductor thin film within a continuous wavelength λ range, and obtains the IF displacement difference between the incident wavelength of the n-type semiconductor thin film and the left-handed and right-handed circularly polarized light based on the spot position information, and transmits it to the inversion calculation module.

[0009] Step 2b: The transmission spectrum acquisition module uses a spectral measurement device to measure the transmission spectrum data of the n-type semiconductor thin film under left-handed and right-handed circularly polarized light at a continuous wavelength λ, and then transmits it to the inversion calculation module.

[0010] Step 3: The inversion calculation module substitutes the IF shift difference and transmission spectrum data into the evaluation function of the dielectric function of the n-type semiconductor thin film, performs inversion calculation, and takes the complex refractive index corresponding to the minimum of the evaluation function as the complex refractive index of the n-type semiconductor thin film. And transmit it to the photoconductivity and absorption coefficient calculation module;

[0011] Step 4: The photoconductivity and absorption coefficient calculation module calculates the photoconductivity and absorption coefficient based on the complex refractive index of the n-type semiconductor thin film. The photoconductivity and absorption coefficient of the n-type semiconductor thin film were calculated.

[0012] Through the above design, this invention first obtains the IF displacement difference of the n-type semiconductor thin film using an IF displacement measurement device, and then obtains the transmission spectrum data of the n-type semiconductor thin film using a spectral measurement device. Next, it performs inversion calculations on the IF displacement difference and transmission spectrum data using an evaluation function to calculate the complex refractive index of the n-type semiconductor thin film. Finally, it calculates the photoconductivity and absorption coefficient of the n-type semiconductor thin film based on the complex refractive index. This achieves accurate and non-destructive measurement of the photoconductivity and absorption coefficient of the n-type semiconductor thin film.

[0013] This invention breaks the coupling between optical constants and geometric thickness in single measurements by combining IF displacement difference measurement and transmission spectroscopy measurement, and achieves high-precision synchronous extraction of photoconductivity and absorption coefficient. It effectively reduces the dependence of traditional transmission methods on film thickness uniformity and background noise, and significantly improves the detection limit for n-type semiconductor transparent films.

[0014] Preferably, in step 2a, when measuring using the IF displacement measuring device, the n-type semiconductor thin film structure to be tested is the substrate layer-n-type semiconductor thin film layer-dielectric layer; the n-type semiconductor thin film layer is an n-type semiconductor thin film layer deposited on the substrate layer.

[0015] Preferably, in step 3, the evaluation function expression for the dielectric function of the n-type semiconductor thin film is:

[0016] ;

[0017] in, The total number of incident wavelengths For the incident wavelength index, The complex refractive index of the n-type semiconductor thin film is... This is the measured value of the IF displacement difference. This is the theoretical value of the IF displacement difference. These are theoretical values ​​from transmission spectral data. These are measured values ​​from transmission spectral data. This is the evaluation function.

[0018] As a preferred embodiment, the calculation expression for the theoretical value of the IF displacement difference is as follows:

[0019] (1);

[0020] (2);

[0021] (3);

[0022] in, This represents the IF shift under right-handed circularly polarized light. This represents the IF shift under left-handed circularly polarized light. This represents the theoretical value of the IF displacement difference under left- and right-hand circularly polarized light. Angle of incidence Let be the incident light wave vector. , Let be the reflection coefficient of s-polarized light. Let be the reflection coefficient of p-polarized light. For the phase of p-polarized light, Let be the phase of the s-polarized light. Indicates the wavelength of the incident light;

[0023] The theoretical value of the transmission spectral data is calculated using the following expression:

[0024] (11).

[0025] Preferably, the reflection and transmission coefficients for p-polarized light and s-polarized light are respectively:

[0026] (4);

[0027] (5);

[0028] (6);

[0029] (7);

[0030] (8);

[0031] (9);

[0032] (10);

[0033] Where b represents the substrate layer, m represents the n-type semiconductor thin film layer, and a represents the dielectric layer. Indicates the phase difference. This represents the reflection coefficient under the BM combination. This represents the reflection coefficient under the ma combination. This represents the transmission coefficient under the BM combination. This represents the transmission coefficient under the ma combination. This represents the complex refractive index of an n-type semiconductor thin film. The refractive index of the dielectric layer, d represents the refractive index of the substrate layer, and d represents the thickness of the n-type semiconductor thin film layer. For imaginary units, Let be the base of the natural logarithm function. The incident angle at which the light enters the basal layer. The incident angle is the incident angle onto the n-type semiconductor thin film layer. The incident angle is the incident angle into the dielectric layer. The reflection coefficient for p-polarized or s-polarized light. is the transmission coefficient for p-polarized or s-polarized light.

[0034] Preferably, in step 4, the photoconductivity of the n-type semiconductor thin film is... The calculation expression is:

[0035] (13);

[0036] (14);

[0037] (15);

[0038] (16);

[0039] (17);

[0040] in, The vacuum permittivity, The incident light angular frequency, The speed of light in a vacuum. The incident wavelength, For imaginary units, Photoconductivity The real part, Photoconductivity The imaginary part, Let be the real part of the complex permittivity. This represents the imaginary part of the complex permittivity. Let be the complex refractive index of the n-type semiconductor thin film. The extinction coefficient of an n-type semiconductor thin film;

[0041] The expression for calculating the absorption coefficient of the n-type semiconductor thin film is as follows:

[0042] (18);

[0043] in, To be at the incident wavelength The absorption coefficient below.

[0044] Preferably, in step 2a, the incident angle and incident point remain unchanged during the IF displacement difference measurement process.

[0045] In step 2b, during the transmission spectral data measurement process, the incident angle and incident point remain unchanged.

[0046] The beneficial effects of this invention are:

[0047] (1) This invention utilizes the extreme sensitivity of IF displacement to interface phase changes, which can accurately reflect the imaginary part of the complex refractive index of the thin film surface / interface (related to the extinction coefficient), while the transmission spectrum mainly reflects the absorption characteristics of the bulk material. The combination of the two can break the coupling between optical constants and geometric thickness in single measurement, and achieve high-precision synchronous extraction of photoconductivity (real / imaginary part) and absorption coefficient;

[0048] (2) This invention utilizes the significant amplification effect of IF displacement near the critical angle of total internal reflection (up to the order of beam width), which can convert the weak dielectric response of nanoscale thin films into easily detectable macroscopic displacement signals. When combined with transmission spectroscopy, it can effectively reduce the dependence of traditional transmission methods on film thickness uniformity and background noise, and significantly improve the detection limit for n-type semiconductor transparent thin films. Attached Figure Description

[0049] Figure 1 This is a flowchart of the method of the present invention;

[0050] Figure 2 This is a diagram of the IF displacement structure of the semiconductor thin film in the embodiment;

[0051] Figure 3 This is a measurement diagram of the IF displacement device in the embodiment;

[0052] Figure 4 The complex refractive index of the ITO thin film obtained in the examples at different wavelengths;

[0053] Figure 5 These are the photoconductivities of the n-type semiconductor thin film at different wavelengths in the embodiments;

[0054] Figure 6 It represents the absorption coefficient of the n-type semiconductor thin film at different wavelengths in the embodiments. Detailed Implementation

[0055] The present invention will be further described in detail below with reference to the accompanying drawings and specific examples. The following embodiments or drawings are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0056] like Figure 1 As shown, a method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film includes the following steps:

[0057] Step 1: Construct a photoconductivity and absorption coefficient detection system for n-type semiconductor thin films. This photoconductivity and absorption coefficient detection system is equipped with an IF shift difference acquisition module and a transmission spectrum acquisition module. The IF shift difference acquisition module and the transmission spectrum acquisition module are connected to the same inversion calculation module, which is connected to a photoconductivity and absorption coefficient calculation module.

[0058] Step 2a: The IF displacement difference acquisition module uses an IF displacement measuring device to measure the position information of the light spot incident on the n-type semiconductor thin film with left-handed and right-handed circularly polarized light within a continuous wavelength range λ. Based on the light spot position information, it obtains the IF displacement difference between the incident wavelength of the n-type semiconductor thin film and the left-handed and right-handed circularly polarized light, such as... Figure 2 As shown, it is passed to the inversion calculation module;

[0059] Step 2b: The transmission spectrum acquisition module uses a spectral measurement device to measure the transmission spectrum data of the n-type semiconductor thin film under left-handed and right-handed circularly polarized light at a continuous wavelength λ, and then transmits it to the inversion calculation module.

[0060] During the measurement, the incident angle and incident point remain unchanged.

[0061] Step 3: The inversion calculation module substitutes the IF shift difference and transmission spectrum data into the evaluation function of the dielectric function of the n-type semiconductor thin film, performs inversion calculation, and takes the complex refractive index corresponding to the minimum of the evaluation function as the complex refractive index of the n-type semiconductor thin film. And transmit it to the photoconductivity and absorption coefficient calculation module;

[0062] Step 4: The photoconductivity and absorption coefficient calculation module calculates the photoconductivity and absorption coefficient based on the complex refractive index of the n-type semiconductor thin film. The photoconductivity and absorption coefficient of the n-type semiconductor thin film were calculated.

[0063] In step 2a, when the measurement is performed using the IF displacement measuring device, the n-type semiconductor thin film structure to be tested is the substrate layer-n-type semiconductor thin film layer-dielectric layer; the n-type semiconductor thin film layer is an n-type semiconductor thin film layer deposited on the substrate layer.

[0064] In step 3, the evaluation function expression for the dielectric function of the n-type semiconductor thin film is:

[0065] ;

[0066] in, The total number of incident wavelengths For the incident wavelength index, The complex refractive index of the n-type semiconductor thin film is... This is the measured value of the IF displacement difference. This is the theoretical value of the IF displacement difference. These are theoretical values ​​from transmission spectral data. These are measured values ​​from transmission spectral data. This is the evaluation function.

[0067] The formula for calculating the theoretical value of the IF displacement difference is as follows:

[0068] (1);

[0069] (2);

[0070] (3);

[0071] in, This represents the IF shift under right-handed circularly polarized light. This represents the IF shift under left-handed circularly polarized light. This represents the theoretical value of the IF displacement difference under left- and right-hand circularly polarized light. Angle of incidence Let be the incident light wave vector. , Let be the reflection coefficient of s-polarized light. Let be the reflection coefficient of p-polarized light. For the phase of p-polarized light, Let be the phase of the s-polarized light. Indicates the wavelength of the incident light;

[0072] The theoretical value of the transmission spectral data is calculated using the following expression:

[0073] (11).

[0074] For p-polarized light and s-polarized light, the reflection and transmission coefficients are respectively:

[0075] (4);

[0076] (5);

[0077] (6);

[0078] (7);

[0079] (8);

[0080] (9);

[0081] (10);

[0082] Where b represents the substrate layer, m represents the n-type semiconductor thin film layer, and a represents the dielectric layer. Indicates the phase difference. This represents the reflection coefficient under the BM combination. This represents the reflection coefficient under the ma combination. This represents the transmission coefficient under the BM combination. This represents the transmission coefficient under the ma combination. This represents the complex refractive index of an n-type semiconductor thin film. The refractive index of the dielectric layer, d represents the refractive index of the substrate layer, and d represents the thickness of the n-type semiconductor thin film layer. For imaginary units, Let be the base of the natural logarithm function. The incident angle at which the light enters the basal layer. The incident angle is the incident angle onto the n-type semiconductor thin film layer. The incident angle is the incident angle into the dielectric layer. The reflection coefficient for p-polarized or s-polarized light. is the transmission coefficient for p-polarized or s-polarized light.

[0083] In step 4, the photoconductivity of the n-type semiconductor thin film... The calculation expression is:

[0084] (13);

[0085] (14);

[0086] (15);

[0087] (16);

[0088] (17);

[0089] in, The vacuum permittivity, The incident light angular frequency, The speed of light in a vacuum. The incident wavelength, For imaginary units, Photoconductivity The real part, Photoconductivity The imaginary part, Let be the real part of the complex permittivity. This represents the imaginary part of the complex permittivity. Let be the complex refractive index of the n-type semiconductor thin film. The extinction coefficient of an n-type semiconductor thin film;

[0090] The expression for calculating the absorption coefficient of the n-type semiconductor thin film is as follows:

[0091] (18);

[0092] in, To be at the incident wavelength The absorption coefficient below.

[0093] like Figure 3 As shown, the IF displacement measuring device is equipped with a laser, a half-wave plate, a first focusing lens, a first polarizer, a quarter-wave plate, a second focusing lens, a second polarizer, and a camera.

[0094] The laser emits incident laser light of a corresponding wavelength. The incident laser light passes through a half-wave plate, a first focusing lens, a first polarizer, and a quarter-wave plate to reach the thin film under test. The thin film under test reflects the light to generate reflected light, which then passes through a second polarizer and a second focusing lens before being captured by the camera.

[0095] This embodiment uses a substrate-n-type semiconductor thin film-dielectric structure model. Specifically, the substrate is BK7 glass, the n-type semiconductor thin film is an ITO thin film, and the dielectric is air. The thickness of the thin film is measured using an ellipsometer. The incident wavelength is selected to be 400nm~700nm. Figure 4 To obtain the complex refractive index by the method described in this invention, the photoconductivity of the ITO thin film is obtained by using equations (16), (17), and (14) as follows: Figure 5 As shown, where c=3* m / s, F / m. Figure 6 ν represents the absorption coefficient of the thin film at different wavelengths.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film, characterized in that, Includes the following steps: Step 1: Construct a photoconductivity and absorption coefficient detection system for n-type semiconductor thin films. This photoconductivity and absorption coefficient detection system is equipped with an IF shift difference acquisition module and a transmission spectrum acquisition module. The IF shift difference acquisition module and the transmission spectrum acquisition module are connected to the same inversion calculation module, which is connected to a photoconductivity and absorption coefficient calculation module. Step 2a: The IF displacement difference acquisition module uses the IF displacement measurement device to measure the spot position information of left-handed and right-handed circularly polarized light incident on the n-type semiconductor thin film within a continuous wavelength λ range, and obtains the IF displacement difference between the incident wavelength of the n-type semiconductor thin film and the left-handed and right-handed circularly polarized light based on the spot position information, and transmits it to the inversion calculation module. Step 2b: The transmission spectrum acquisition module uses a spectral measurement device to measure the transmission spectrum data of the n-type semiconductor thin film under left-handed and right-handed circularly polarized light at a continuous wavelength λ, and then transmits it to the inversion calculation module. Step 3: The inversion calculation module substitutes the IF shift difference and transmission spectrum data into the evaluation function of the dielectric function of the n-type semiconductor thin film, performs inversion calculation, and takes the complex refractive index corresponding to the minimum of the evaluation function as the complex refractive index of the n-type semiconductor thin film. And transmit it to the photoconductivity and absorption coefficient calculation module; Step 4: The photoconductivity and absorption coefficient calculation module calculates the photoconductivity and absorption coefficient based on the complex refractive index of the n-type semiconductor thin film. The photoconductivity and absorption coefficient of the n-type semiconductor thin film were calculated.

2. The method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film according to claim 1, characterized in that: In step 2a, when the measurement is performed using the IF displacement measuring device, the n-type semiconductor thin film structure to be tested is the substrate layer-n-type semiconductor thin film layer-dielectric layer; the n-type semiconductor thin film layer is an n-type semiconductor thin film layer deposited on the substrate layer.

3. The method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film according to claim 1, characterized in that: In step 3, the evaluation function expression for the dielectric function of the n-type semiconductor thin film is: ； in, The total number of incident wavelengths, For the incident wavelength index, The complex refractive index of the n-type semiconductor thin film is given by [reference to a specific parameter]. This is the measured value of the IF displacement difference. This is the theoretical value of the IF displacement difference. These are theoretical values ​​from transmission spectral data. These are measured values ​​from transmission spectral data. This is the evaluation function.

4. The method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film according to claim 3, characterized in that: The formula for calculating the theoretical value of the IF displacement difference is as follows: （1）； （2）； （3）； in, This represents the IF shift under right-handed circularly polarized light. This represents the IF shift under left-handed circularly polarized light. This represents the theoretical value of the IF displacement difference under left- and right-hand circularly polarized light. Angle of incidence Let be the incident light wave vector. , Let be the reflection coefficient of s-polarized light. Let be the reflection coefficient of p-polarized light. For the phase of p-polarized light, Let be the phase of the s-polarized light. Indicates the wavelength of the incident light; The theoretical value of the transmission spectral data is calculated using the following expression: （11）。 5. The method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film according to claim 4, characterized in that: in, For p-polarized light and s-polarized light, the reflection and transmission coefficients are respectively: （4）； （5）； （6）； （7）； （8）； （9）； （10）； Where b represents the substrate layer, m represents the n-type semiconductor thin film layer, and a represents the dielectric layer. Indicates the phase difference. This represents the reflection coefficient under the BM combination. This represents the reflection coefficient under the ma combination. This represents the transmission coefficient under the BM combination. This represents the transmission coefficient under the ma combination. This represents the complex refractive index of an n-type semiconductor thin film. The refractive index of the dielectric layer, d represents the refractive index of the substrate layer, and d represents the thickness of the n-type semiconductor thin film layer. For imaginary units, Let be the base of the natural logarithm function. The incident angle at which the light enters the basal layer. The incident angle is the incident angle onto the n-type semiconductor thin film layer. The incident angle is the incident angle into the dielectric layer. The reflection coefficient for p-polarized or s-polarized light. is the transmission coefficient for p-polarized or s-polarized light.

6. The method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film according to claim 1, characterized in that: In step 4, the photoconductivity of the n-type semiconductor thin film... The calculation expression is: （13）； （14）； （15）； （16）； （17）； in, The vacuum permittivity, The incident light angular frequency, The speed of light in a vacuum. The incident wavelength, For imaginary units, Photoconductivity The real part, Photoconductivity The imaginary part, Let be the real part of the complex permittivity. This represents the imaginary part of the complex permittivity. Let be the complex refractive index of the n-type semiconductor thin film. The extinction coefficient of an n-type semiconductor thin film; The expression for calculating the absorption coefficient of the n-type semiconductor thin film is as follows: （18）； in, To be at the incident wavelength The absorption coefficient below.

7. The method for detecting the photoconductivity and absorption coefficient of an n-type semiconductor thin film according to claim 1, characterized in that: In step 2a, during the IF displacement difference measurement, the incident angle and incident point remain unchanged; In step 2b, during the transmission spectral data measurement process, the incident angle and incident point remain unchanged.

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