A method for measuring the surface recombination velocity of a semiconductor material

Abstract

The application discloses a kind of semiconductor material surface recombination rate measurement method, comprising the following steps: using laser source to generate pump light to irradiate the semiconductor sample to be measured, the change rate of the luminescence signal generated by sample after laser is closed is collected, the luminescence intensity curve decaying with time is obtained, laser power is changed, and the response of the sample to be measured decaying curve with time is obtained from the three-dimensional image of intensity-time-power, the decay constant under different power intensities is normalized and fitted, and then the constant set is fitted using surface recombination model, and the surface recombination rate value of the semiconductor sample is extracted based on the set of parameters.The semiconductor material surface recombination rate measurement extraction method of the application can effectively measure surface properties, non-destructive non-contact surface recombination rate is obtained, and has application value for on-line detection of semiconductor preparation.

Description

Technical Field

[0001] This invention belongs to the field of non-contact measurement technology of semiconductor materials, specifically a method for measuring the surface recombination rate of semiconductor materials. Background Technology

[0002] Semiconductor materials are the cornerstone of the modern electronics and optoelectronics industry, and their performance directly determines the key performance indicators of devices. Whether it is solar cells used for energy conversion, microprocessors and light-emitting diodes used for information processing and transmission, or infrared detectors used for detection tasks, their efficiency, speed, and sensitivity are all profoundly related to the properties of the materials.

[0003] Among the many factors influencing the photoelectric properties of materials, defects and dangling bonds generated on the material surface due to lattice termination form recombination centers, causing charge carriers to recombine before reaching the collection region—a process known as surface recombination. The surface recombination rate is a key physical parameter for quantifying the strength of this process. Accurately measuring the surface recombination rate is a critical technology. Traditional electrical probe testing methods require ohmic contact with the sample surface, which may introduce contact stress damage or contamination. Microprobe technology, when measuring the electrical parameters of internal devices, typically requires removing the surface layer to achieve direct contact, potentially damaging the tested structure or altering its initial state. Furthermore, some destructive testing techniques based on physical probes, such as probe card contact in wafer probing, also carry the risk of wafer material damage due to probe wear or excessive contact force.

[0004] Therefore, developing a non-destructive, non-contact method for measuring surface recombination rate, providing an online detection approach that does not require surface damage or property alteration, is crucial for a deeper understanding of recombination mechanisms, accurate identification of performance bottlenecks, and guidance of process improvements. This has become a deep-seated need driving the development of high-performance semiconductor devices.

[0005] In summary, current methods for measuring surface recombination rates still have room for improvement in terms of measurement directness, result accuracy, and application robustness. There is an urgent need for a new method capable of non-destructive, non-contact extraction of this key parameter to meet the pressing need for in-situ characterization of surface properties in the development of advanced semiconductor materials and devices. Summary of the Invention

[0006] The purpose of this invention is to provide a method for measuring the surface recombination rate of semiconductor materials. Addressing the shortcomings of existing technologies, this invention aims to provide a non-destructive, non-contact method for measuring the surface recombination rate. This invention constructs a dedicated surface recombination exponential decay model, thereby achieving accurate and stable quantitative extraction of the surface recombination rate without relying heavily on initial data fitting. Therefore, a method for measuring the surface recombination rate of semiconductor materials is provided.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a method for measuring the surface recombination rate of a semiconductor material, characterized in that the method comprises the following steps:

[0008] S1. Use a laser source to generate pump light to irradiate the semiconductor sample under test, collect the rate of change of the emission signal generated by the sample after the laser is turned off over time, and obtain the emission intensity curve that decays over time.

[0009] S2. Change the laser power and repeat S1 to form a pump-injection condition and obtain a set of response decay curves of the sample under test over time.

[0010] S3. Normalize the series of response curves and extract the exponential decay constant value corresponding to each curve to form a decay constant array.

[0011] S4. Substitute the decay constant into Equation 1 and perform fitting verification. The model characterizes the relationship between surface recombination rate and carrier concentration. The physical model of surface recombination rate is an exponentially dependent model, which is specifically expressed as follows:

[0012] (1)

[0013] Where A is the reciprocal of the attenuation constant, and C is the value of the attenuation constant of the stationary body. For surface recombination rate, For sample thickness, To inject carrier concentration, Characteristic concentration;

[0014] Plot the correlation between A and normalized carrier density, and fit the graph at different power injections to obtain parameters such as surface recombination rate, characteristic carrier concentration, and stationary decay constant.

[0015] S5. Analyze the physical parameters and extract the surface recombination rate value of the semiconductor sample based on the set of parameters.

[0016] Furthermore, in step S1, after acquiring the response signal, information about the response signal obtained by repeatedly measuring the signal and averaging it is included to improve the signal-to-noise ratio.

[0017] Furthermore, the falling edge time of the laser source in step S1 is less than 20 nanoseconds.

[0018] Furthermore, the different power levels mentioned in step S2 include at least one high power level, under which the excess carrier concentration generated by injection is significantly higher than the intrinsic carrier concentration of the semiconductor material, thereby forming a large injection condition; the pump variable injection condition is used to excite the surface recombination effect.

[0019] Furthermore, the normalization process described in step S3 involves using the peak intensity of the optical response signal at each power level and the calculated maximum excess carrier concentration as a benchmark for normalization.

[0020] Furthermore, in step S3, the normalized decay curves of the sample under different injection powers are obtained using the following single exponential decay function to obtain the decay constants at different injection levels.

[0021] (2),

[0022] Where I PLnorm To normalize the sample luminescence intensity, t eff The effective attenuation constant value is generated by the variable power injection condition of the sample.

[0023] Furthermore, in step S5, based on the large injection condition, the initial surface recombination rate value in the surface recombination rate model is used as the measurement result of the surface recombination rate.

[0024] In view of the above technical features, the present invention has the following beneficial effects:

[0025] 1. The method for measuring the surface recombination rate of semiconductor materials according to the present invention has the following beneficial effects: The present invention utilizes variable power measurement to obtain the luminescence intensity curve decaying over time and the corresponding physical model normalized single-exponential fitting to extract the decay constant. This is a typical optical method, and there is no potential risk of contact with or damage to the sample under test. Based on the surface recombination exponential decay model, the present invention achieves accurate and stable quantitative extraction of the surface recombination rate without relying heavily on initial data fitting. This helps to optimize the front-end processing and performance of materials. Attached Figure Description

[0026] Figure 1 This is a flowchart of a method for measuring the surface recombination rate of a semiconductor material in specific embodiment 1;

[0027] Figure 2 This is a schematic diagram of the response decay curves of sample A (a) and sample B (b) in specific embodiment 1;

[0028] Figure 3 The relationship between the reciprocal of the attenuation constant and the normalized photogenerated carrier concentration is shown in Specific Example 1. The dashed line represents the surface recombination rate extracted using the fitted curve of Formula (1). Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0030] See Figures 1 to 3 Specific embodiment 1: This embodiment 1 provides a method for measuring the surface recombination rate of a semiconductor material, characterized in that the method includes the following steps:

[0031] S1. Use a laser source to generate pump light to irradiate the semiconductor sample under test, collect the rate of change of the emission signal generated by the sample after the laser is turned off over time, and obtain the emission intensity curve that decays over time.

[0032] Step S1, after acquiring the response signal, also includes information on the response signal obtained by repeatedly measuring the signal and averaging it, in order to improve the signal-to-noise ratio.

[0033] The falling edge time of the laser source is less than 20 nanoseconds, ensuring a time resolution on the order of 0.1 microseconds.

[0034] S2. Change the laser power and repeat S1 to form a pump-injection condition and obtain a set of response decay curves of the sample under test over time.

[0035] The different power levels mentioned in step S2 include at least one high power level, under which the excess carrier concentration generated by injection is significantly higher than the intrinsic carrier concentration of the semiconductor material, thereby forming a large injection condition; the pump variable injection condition is used to excite the surface recombination effect.

[0036] S3. Normalize the series of response curves and extract the exponential decay constant value corresponding to each curve to form a decay constant array.

[0037] The normalization process described in step S3 involves using the peak intensity of the optical response signal at each power level and the calculated maximum excess carrier concentration as a benchmark for normalization.

[0038] S4. Substitute the decay constant into Equation 1 and perform fitting verification. The model characterizes the relationship between surface recombination rate and carrier concentration. The physical model of surface recombination rate is an exponentially dependent model, which is specifically expressed as follows:

[0039] (1)

[0040] Where A is the reciprocal of the attenuation constant, and C is the value of the attenuation constant of the stationary body. For surface recombination rate, For sample thickness, To inject carrier concentration, Characteristic concentration;

[0041] Plot the correlation between A and normalized carrier density, and fit the graph at different power injections to obtain parameters such as surface recombination rate, characteristic carrier concentration, and stationary decay constant.

[0042] S5. Analyze the physical parameters and extract the surface recombination rate value of the semiconductor sample based on this set of parameters. In step S5, under the large injection condition, the initial surface recombination rate value in the surface recombination rate model is used as the measurement result of the surface recombination rate.

[0043] As a preferred embodiment of the above method, a 1064 nm laser was used as the excitation source, with powers of 50 mW, 75 mW, 125 mW, 200 mW, and 250 mW, respectively. An indium antimonide detector was used to detect the emitted signal. Two samples (labeled #A and #B) had thicknesses of 5.7 μm and 7.4 μm, respectively. The purpose was to accurately quantify the extracted surface recombination rate during the measurement process, ensuring that the extracted surface recombination rate value directly reflects the sample surface quality. After measurement and comparison, relevant pre-growth processes can be optimized and improved.

[0044] The decay curve of the sample's photoresponse over time was measured. The laser power was then controlled to determine the carrier injection rate. (See attached image.) Figure 2 Normalized decay curves of two HgCdTe samples under different injection powers are shown, and the decay constants at different injection levels are obtained using the following single exponential decay function.

[0045] (2),

[0046] Where I PLnorm To normalize the sample luminescence intensity, t eff The effective attenuation constant value for the sample is generated by the variable power injection condition. For time (corresponding) Figure 2 (x-axis)

[0047] The surface recombination rate varies exponentially with surface potential or surface carrier concentration. Specifically, it is described as follows:

[0048] A (1)

[0049] Where A is the reciprocal of the attenuation constant, and C is the value of the attenuation constant of the stationary body. For surface recombination rate, For sample thickness, To inject carrier concentration, The characteristic concentration is calculated. A correlation image between A and normalized carrier density is plotted, and Equation 1 is used to fit and obtain parameters such as surface recombination rate and characteristic concentration, as shown in the attached figure. Figure 3 As shown in the figure. The parameters obtained, such as surface recombination rate, characteristic concentration, and reciprocal value of the stationary decay constant, are shown in Table 1.

[0050] Table 1 Parameter values ​​of surface composite model

[0051] sample <![CDATA[S0(cm / s)]]> <![CDATA[n c (cm -3 )]]> 1 / C(μs) #A 271 0.101 2.27 #B 520 0.136 2.08

[0052] In the surface composite model, and The value of can directly reflect the surface quality of the sample. The smaller the value, the fewer recombination channels on the sample surface, which is more conducive to improving device performance; The smaller the value, the lower the impact of the surface on the device performance. Therefore, the relevant parameters provided by this model can more directly and accurately achieve in-situ characterization of the surface of semiconductor materials and make a preliminary judgment on the impact of surface quality on device performance.

[0053] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for measuring the surface recombination rate of a semiconductor material, characterized in that, The method includes the following steps: S1. Use a laser source to generate pump light to irradiate the semiconductor sample under test, collect the rate of change of the emission signal generated by the sample after the laser is turned off over time, and obtain the emission intensity curve that decays over time. S2. Change the laser power and repeat S1 to form a pump-injection condition and obtain a set of response decay curves of the sample under test over time. S3. Normalize a series of response curves and extract the exponential decay constant value corresponding to each curve to form a decay constant array. S4. Substitute the decay constant into the surface recombination rate physical model and perform fitting verification. The model characterizes the correlation between the surface recombination rate and the carrier concentration. The surface recombination rate physical model is an exponentially dependent model, and its specific expression is as follows: （1）， Where A is the reciprocal of the attenuation constant, and C is the value of the attenuation constant of the stationary body. For surface recombination rate, For sample thickness, To inject carrier concentration, Characteristic concentration; Plot the correlation between A and normalized photogenerated carrier concentration, and fit the data at different power injections to obtain the surface recombination rate, characteristic carrier concentration, and stationary decay constant. S5. Obtain the surface recombination rate, characteristic carrier concentration, and stationary decay constant values ​​from step S4, and extract the surface recombination rate value of the semiconductor sample.

2. The method for measuring the surface recombination rate of a semiconductor material according to claim 1, characterized in that, Step S1, after acquiring the response signal, also includes information on the response signal obtained by repeatedly measuring the signal and averaging it, in order to improve the signal-to-noise ratio.

3. The method for measuring the surface recombination rate of a semiconductor material according to claim 1, characterized in that, In step S1, the falling edge time of the laser source is less than 20 nanoseconds.

4. The method for measuring the surface recombination rate of a semiconductor material according to claim 1, characterized in that, In step S2, at least one of the different power levels is a high power level. Under this high power level, the excess carrier concentration generated by the injection is significantly higher than the intrinsic carrier concentration of the semiconductor material, thereby forming a large injection condition. The pump-variable injection condition is used to excite the surface recombination effect.

5. The method for measuring the surface recombination rate of a semiconductor material according to claim 1, characterized in that, The normalization process described in step S3 involves using the peak intensity of the optical response signal at each power level and the calculated maximum excess carrier concentration as a benchmark for normalization.

6. The method for measuring the surface recombination rate of a semiconductor material according to claim 1, characterized in that, In step S3, the normalized decay curves of the sample under different injection powers are obtained using the following single exponential decay function to obtain the decay constants at different injection levels. （2）， Where I PLnorm To normalize the sample luminescence intensity, t eff Here, t represents the effective attenuation constant value of the sample, and t represents time. The variable power injection condition of the sample will generate a set of effective attenuation constant values.

7. The method for measuring the surface recombination rate of a semiconductor material according to claim 4, characterized in that, In step S5, based on the large injection condition, the initial surface recombination rate value in the surface recombination rate model is used as the measurement result of the surface recombination rate.

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