CN115020168A - Method for controlling NEA GaN photocathode quantum efficiency in real time - Google Patents
Method for controlling NEA GaN photocathode quantum efficiency in real time Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 27
- 241000769223 Thenea Species 0.000 claims abstract description 8
- 230000003287 optical effect Effects 0.000 claims abstract description 4
- 230000008033 biological extinction Effects 0.000 claims description 2
- 239000013078 crystal Substances 0.000 description 2
- 229910052594 sapphire Inorganic materials 0.000 description 2
- 239000010980 sapphire Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 229910002704 AlGaN Inorganic materials 0.000 description 1
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- H—ELECTRICITY
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- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/12—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes
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- H—ELECTRICITY
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Abstract
The invention discloses a method for controlling quantum efficiency of an NEA GaN photocathode in real time. The specific method comprises the following steps: step 1, establishing a temperature calibration model; step 2, measuring quantum efficiency QE of GaN photocathode sample 0 Wavelength λ, wavelength of 0 And temperature T 0 Fitting sample parameters according to the data; step 3, inputting the working optical wavelength lambda, the target quantum efficiency QE and the sample parameters obtained by fitting into a previously established temperature calibration model to calculate the theoretical temperature T 1 (ii) a Step 4, setting the deviation degree as S, and measuring T 1 Quantum efficiency QE of GaN photocathode at temperature 1 And calculating to obtain a deviation S 1 If S is 1 Less than a set deviation S, and an output temperature T equal to T 1 If S is 1 If it is greater than the set value, according to T 1 ，QE 1 Continuously fitting and correcting sample parameters, and calculating again to obtain the temperature T 2 Measuring T 2 Amount under the conditionSub efficiency QE 2 And comparing the deviation S 2 And a set value S; and 5, circulating the steps until the deviation degree is smaller than a set value, and outputting the optimal temperature T corresponding to the target quantum efficiency QE. The invention can control the quantum efficiency of the NEA GaN photocathode in real time by automatically adjusting the temperature, has the characteristics of self-calibration function and flexibility and variability, and improves the working performance of the NEA GaN photocathode.
Description
Technical Field
The invention belongs to the field of semiconductor optoelectronic devices, and particularly discloses a method for controlling quantum efficiency of an NEA GaN photocathode in real time.
Background
Photocathodes are devices that emit electrons based on the photoelectric effect and have important application and development prospects in military and civil applications, such as: detectors, fire alarms, biosensors, etc. GaN, as a third generation semiconductor, has the advantages of large forbidden band width, high quantum efficiency, stable chemical and physical properties, etc., and exhibits excellent electron transfer and transition characteristics, and has become a hot spot for research on photocathodes in recent years. At present, the Cs/O layer is adsorbed on the surface of the GaN photocathode to cause the bending of the energy band, so that the bottom of the conduction band is higher than the vacuum level, so-called negative electron affinity is formed, and electrons are easier to escape into the vacuum, so that the quantum efficiency of the GaN photocathode is improved, which is the currently commonly used NEA GaN photocathode.
An important parameter for measuring the cathode performance of NEA GaN is the quantum efficiency, which is defined as the ratio of the average number of photons generated per unit time to the number of incident photons, and can be actually calculated from the output photocurrent and the incident photon flow, and is related to many factors, such as the incident photon energy, the temperature, and so on. When the NEA GaN photocathode is used, a stable electron current output is often needed, and when external conditions are not changed, the stability of the quantum efficiency of the cathode is ensured, however, in the using process, along with the falling of the Cs/O layer on the surface of the GaN photocathode, the quantum efficiency is rapidly reduced, so that how to stabilize the quantum efficiency of the NEA GaN photocathode becomes a problem to be solved urgently.
Disclosure of Invention
In view of the above problems, the present invention aims to provide a method for controlling the quantum efficiency of an NEA GaN photocathode in real time by establishing a temperature calibration model, so that the quantum efficiency of the NEA GaN photocathode is controllable and stable as much as possible.
In order to achieve the purpose, the invention adopts the technical scheme that: a method for controlling NEA GaN photocathode quantum efficiency in real time comprises the following steps:
step 1, establishing a temperature calibration model;
step 2, measuring quantum efficiency QE of GaN photocathode sample 0 Wavelength λ, wavelength of 0 And temperature T 0 Fitting sample parameters according to the data;
step 3, inputting the working optical wavelength lambda, the target quantum efficiency QE and the sample parameters obtained by fitting into a previously established temperature calibration model to calculate the theoretical temperature T 1 ；
Step 4, setting the deviation degree as S, and measuring T 1 Quantum efficiency QE of GaN photocathode at temperature 1 And calculating to obtain the deviation S 1 If S is 1 Less than a set deviation S, and an output temperature T equal to T 1 If S is 1 If it is greater than the set value, according to T 1 ，QE 1 Continuously fitting the sample parameters and correcting, and then repeating the step 3 to calculate again to obtain the temperature T 2 Measuring T 2 Quantum efficiency QE under conditions 2 And comparing the deviation S 2 And a set value;
and 5, circulating the steps until the deviation degree is smaller than a set value, and outputting the optimal temperature T corresponding to the quantum efficiency QE.
Furthermore, the method obtains the quantum efficiency by calculating the ratio of the emergent light current to the incident photon current, the wavelength is measured by a spectrometer, and the temperature is measured by a temperature sensor.
Further, the temperature calibration model established by the method is as follows
Wherein a, b, c, alpha 0 Gamma, beta, mu, r, psi are sample related parameters, n is sample refractive index, p is sample extinction coefficient, K is Boltzmann constant, e is electron electric quantity, T is temperature, and unit is K. Gamma is-9.39X 10 -4 About eV/K, beta is about 772K, mu is the electron mobility, and the range is 100-300cm 2 /Vs, r is the electron lifetime, ranging from 2 to 15 ns.
Furthermore, in order to ensure the working performance of the photocathode, the value range of the incident light wavelength λ is 100-365nm, and the working temperature range is 20-600K.
Further, in the method, in order to ensure the correctness of the sample parameters obtained by fitting, the more the data sets m are measured, the more the sample parameters are accurate, but the increase of the number of the data sets affects the operation speed, so m is generally 100-.
Further, the method has a deviation degree of S n ＝|QE n -QE |/QE × 100%, the deviation degree represents the relative deviation of the actually measured quantum efficiency and the target quantum efficiency, and since the quantum efficiency is related to a plurality of parameters, the measurement usually has a certain error, and the deviation degree can be set to be 5% -10%.
Furthermore, the method is automatically executed by a computer, and manual calculation is not needed, so that the real-time purpose is achieved.
In the invention, because the quantum efficiency of the NEA GaN photocathode is related to a plurality of parameters such as escape probability, surface reflectivity and the like, the established temperature calibration model is more complex, the operation speed is influenced, certain influence is exerted on the real-time performance, but the more the parameters are, the higher the accuracy is; the value of the wavelength mainly takes the forbidden bandwidth of GaN into consideration, so that electrons can jump from a valence band to a conduction band; the deviation is set to ensure the accuracy and the real-time performance simultaneously, and is not suitable to be too large, which reduces the accuracy, and is also not suitable to be too small, which increases the operation time; the method is operated by a computer, so that the aim of controlling the quantum efficiency of the NEA GaN photocathode in real time is fulfilled.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings.
Example 1
The GaN photocathode sample substrate is sapphire crystal and 500um thick, the AlN buffer layer is 50nm thick, the GaN electron emission layer is 160nm thick, and the p-type doping concentration is 10 17 cm -3 。
Fig. 1 shows a flow chart of a method for real-time control of the quantum efficiency of an NEA GaN photocathode. From top to bottom, the method comprises the following steps:
1. measuring 100 sets of wavelengths lambda 0 300nm and temperature T 0 Quantum efficiency QE of GaN photocathode sample at 300K 0 And fitting the measured data to obtain sample parameters according to the temperature calibration model.
2. Inputting the optical wavelength lambda of 280nm, the target quantum efficiency QE of 24% and the sample parameters obtained by fitting into a temperature calibration model established before to calculate the theoretical temperature T 1 。
3. Set the degree of deviation S to 6%, measure T 1 Quantum efficiency QE of GaN photocathode under temperature 1 And calculating to obtain the deviation S 1 Is 5%, at this time S 1 Less than 6% of the set deviation, and the output temperature T ═ T 1 ；S 1 If it is greater than the set value, then according to T 1 、QE 1 Continuously fitting the sample parameters and correcting, and then repeating the step 2 to calculate again to obtain the temperature T 2 Measuring T 2 Quantum efficiency QE under conditions 2 And comparing the deviation S 2 And a set point.
4. And (4) circulating the steps until the deviation degree is smaller than a set value, and outputting the optimal temperature T corresponding to the quantum efficiency QE.
Example 2
The GaN photocathode sample substrate is sapphire crystal and 500um thick, the AlGaN buffer layer is 50nm thick, the GaN electron emission layer is 150nm thick, and the p-type doping concentration is 3 multiplied by 10 17 cm -3 。
Fig. 1 shows a flow chart of a method for real-time control of the quantum efficiency of an NEA GaN photocathode. Respectively comprises the following steps from top to bottom:
1. measuring 100 sets of wavelengths lambda 0 300nm and temperature T 0 Quantum efficiency QE of GaN photocathode sample at 280K 0 And fitting the measured data to obtain sample parameters according to the temperature calibration model.
2. Inputting the wavelength lambda of light in operation as 280nm, the target quantum efficiency QE as 20% and the sample parameters obtained by fitting into the previously established temperature calibrationCalculating theoretical temperature T in model 1 。
3. Set the degree of deviation S to 5%, measure T 1 Quantum efficiency QE of GaN photocathode at temperature 1 And calculating to obtain the deviation S 1 Is 6%, at this time S 1 If it is greater than the set value, according to T 1 、QE 1 Continuously fitting the sample parameters and correcting, and then repeating the step 2 to calculate again to obtain the temperature T 2 Measuring T 2 Quantum efficiency QE under conditions 2 And comparing the deviation S 2 And a set point.
4. And (4) circulating the steps until the deviation degree is smaller than a set value, and outputting the optimal temperature T corresponding to the quantum efficiency QE.
The foregoing is a more detailed description of the present invention that is presented in conjunction with specific preferred embodiments, which are not to be construed as limiting the present invention, but rather as follows: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and are intended to be within the scope of the invention.
Claims (6)
1. A method for controlling quantum efficiency of an NEA GaN photocathode in real time comprises the following steps:
step 1, establishing a temperature calibration model;
step 2, measuring quantum efficiency QE of GaN photocathode sample 0 Wavelength lambda of 0 And temperature T 0 Fitting sample parameters according to the data;
step 3, inputting the working optical wavelength lambda, the target quantum efficiency QE and the sample parameters obtained by fitting into a previously established temperature calibration model to calculate the theoretical temperature T 1 ；
Step 4, setting the deviation degree as S, and measuring T 1 Quantum efficiency QE of GaN photocathode at temperature 1 And calculating to obtain a deviation S 1 If S is 1 Less than a set deviation S, and an output temperature T equal to T 1 If S is 1 If it is greater than the set value, according to T 1 ，QE 1 Continuing to fit the sample parameters and correct them, thereafterRepeating the step 3 to calculate the temperature T again 2 Measuring T 2 Quantum efficiency QE under conditions 2 And comparing the deviation S 2 And a set value;
and 5, circulating the steps until the deviation degree is smaller than a set value, and outputting the optimal temperature T corresponding to the quantum efficiency QE. The method is characterized in that the method has a self-calibration function, the processes can be automatically carried out by a computer, and only the target quantum efficiency QE and the specified deviation S need to be input in advance.
2. The method of claim 1, wherein a temperature calibration model is established to control the quantum efficiency of the NEA GaN photocathode in real time by adjusting the temperature.
Wherein a, b, c, alpha 0 Gamma, beta, mu, r, psi are sample related parameters, n is sample refractive index, p is sample extinction coefficient, K is Boltzmann constant, e is electron electric quantity, T is temperature, and unit is K.
3. The method as claimed in claim 1, wherein the wavelength of the used light is 100-365nm, the operating temperature is 20-600K, the wavelength is measured by a spectrometer, and the temperature is measured by an electronic temperature sensor.
4. The method of claim 1 wherein the m sets of data are measured for fitting the sample parameters to ensure the accuracy of the fitted sample parameters.
5. The method of claim 1 wherein the deviation is defined as follows:
S n ＝|QE n -QE|/QE×100％。
6. the method of claim 5 wherein, for a temperature calibration model, if an optimal temperature cannot be obtained once, then calculating sample parameters according to the model and correcting until the deviation is less than a set value, and then outputting the optimal temperature.
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| CN202210484320.3A CN115020168A (en) | 2022-04-27 | 2022-04-27 | Method for controlling NEA GaN photocathode quantum efficiency in real time |
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Application publication date: 20220906 |