A method for measuring the double electron transition rate of donor-bound excitons in semiconductor materials

Abstract

The present invention discloses a method for measuring the double electron transition rate of donor bound excitons in semiconductor materials, and belongs to the field of measurement and characterization of semiconductor materials. The measurement method comprises: 1. measuring the peak intensity of the donor bound exciton peak and the corresponding double electron transition peak in the semiconductor material at each temperature by steady-state photoluminescence spectrum; 2. measuring the lifetime of the donor bound exciton peak at each temperature by time-resolved photoluminescence spectrum; 3. deducing the quantum efficiency of the donor bound exciton peak, and combining it to deducing the radiative recombination lifetime of the donor bound exciton; 4. dividing the relative intensity of the double electron transition peak and the donor bound exciton peak by the radiative recombination lifetime of the donor bound exciton to obtain the double electron transition rate of the donor bound exciton at each temperature. The present invention solves the problem that the double electron transition rate is difficult to measure, and can quickly and accurately obtain the variation law of the double electron transition rate with temperature, which is of great value for studying the physical properties of donor bound excitons and their double electron transitions.

Description

Technical Field

[0001] The invention belongs to the field of measurement and characterization of semiconductor materials, and in particular, relates to a method for measuring the double electron transition rate of donor-bound excitons in semiconductor materials. Background Art

[0002] One of the main differences between semiconductors and metals is that metals have only one main carrier type, i.e., free electrons, while semiconductors have two types of carriers, electrons and holes. Excitons are quasi-particles formed by the mutual attraction of electrons and holes in semiconductor materials through Coulomb interaction. Excitons are usually formed in semiconductor materials when they are stimulated by external excitations (such as light or electric fields). When electrons in the valence band are excited to the conduction band, the remaining holes and electrons in the conduction band can combine to form excitons through Coulomb interaction. Excitons can disappear through radiative recombination or non-radiative recombination. The energy of the photons released by excitons through radiative recombination is equal to the band gap energy minus the binding energy, so the exciton luminescence is usually lower than the luminescence peak of free carrier recombination. Exciton recombination luminescence is the key physical basis of optoelectronic devices such as semiconductor lasers and LEDs. The behavior of excitons in wide bandgap semiconductor materials (such as gallium nitride and aluminum nitride) is crucial to the development of efficient ultraviolet light-emitting devices. In two-dimensional materials (such as graphene and transition metal dichalcogenides), the strong binding and quantization characteristics of excitons provide new directions for quantum information processing. Therefore, the study of excitons is of great significance for understanding the optical and electronic properties of semiconductor materials.

[0003] In actual semiconductor materials, lattice defects, impurities (such as doped impurity atoms) or other local energy fields can further confine excitons to a certain area, forming bound excitons. Figure 1 As shown in the figure, donor-bound excitons are formed when excitons are captured by neutral donor impurities. Donor-bound excitons will emit photons during the radiative recombination process, generating a characteristic luminescence peak. Due to the binding energy of donor-bound excitons, the energy of this peak is generally slightly lower than the luminescence energy of free excitons. The di-electron transition is a competitive process for the normal radiative recombination of donor-bound excitons, similar to a radiative Auger process, in which the donor ends up in an excited state, for example, the easily ionized electron on the donor ends up in the 2s or 2p state. In this process, photons are emitted at an energy difference (E) lower than the normal recombination energy of donor-bound excitons. 2s,p -E 1s) emission. By analyzing the position and intensity of the double electron transition peak, information about the ionization energy of donor impurities in semiconductor materials can be obtained. At the same time, the existence of the double electron transition peak reveals the complexity of multi-electron interactions in the exciton recombination process, which provides in-depth physical information for understanding the carrier recombination mechanism, the luminescence properties of the material, and the exciton dynamics behavior. However, the double electron transition peak intensity is weaker than the donor bound exciton peak, and the double electron transition is one of the many non-radiative recombination processes of donor bound excitons. Therefore, it is currently difficult to measure the double electron transition rate of donor bound excitons in semiconductor materials. Summary of the invention

[0004] In order to solve the above-mentioned problem that it is currently difficult to measure the double electron transition rate of donor bound excitons in semiconductor materials, the purpose of the present invention is to provide a method for measuring the double electron transition rate of donor bound excitons in semiconductor materials. The method is based on photoluminescence, and effectively solves the problem that the double electron transition rate of donor bound excitons is difficult to measure through variable temperature steady-state photoluminescence spectroscopy and time-resolved photoluminescence spectroscopy, and can quickly and accurately obtain the variation law of the double electron transition rate of donor bound excitons with temperature.

[0005] In order to achieve the above purpose, the present invention adopts the following technical scheme:

[0006] A method for measuring the double electron transition rate of donor bound excitons in semiconductor materials comprises the following steps:

[0007] Step 1: Use variable temperature steady-state photoluminescence spectroscopy to measure the steady-state photoluminescence spectrum curve of semiconductor materials at different temperatures, and extract the integrated intensity of the donor-bound exciton peak at each temperature And the integrated intensity of the double electron transition peak corresponding to the donor bound exciton ;

[0008] Step 2: Use variable temperature time-resolved photoluminescence spectroscopy to measure the monochromatic decay curve at the peak of the donor-bound exciton peak of the semiconductor material at different temperatures, and extract the lifetime of the donor-bound exciton peak at each temperature ;

[0009] Step 3: The integrated intensity of the donor-bound exciton peak obtained in step 1 The quantum efficiency of the donor-bound exciton peak is derived , and then the quantum efficiency of the donor-bound exciton peak and the donor-bound exciton peak lifetime obtained in step 2 The radiative recombination lifetime of donor-bound excitons at different temperatures is deduced ;

[0010] Step 4: The integrated intensity of the donor-bound exciton peak at each temperature obtained in step 1 , the integrated intensity of the double electron transition peak corresponding to the donor bound exciton And the radiative recombination lifetime of donor-bound excitons at each temperature obtained in step 3 , we can get the double electron transition rate of donor bound exciton at each temperature .

[0011] Among them, donor-bound excitons are neutral donor-bound excitons formed by excitons being captured by neutral donor impurities, usually denoted as D 0 X; The di-electron transition of donor-bound excitons is a competitive process of the normal radiative recombination of donor-bound excitons, similar to a radiative Auger process, in which the donor is ultimately in an excited state, for example, the easily ionized electron on the donor is ultimately in the 2s or 2p state. In this process, photons with a lower energy difference (E) than the normal donor-bound exciton recombination 2s,p -E 1s ) emission, the luminescence peak corresponding to the double electron transition is usually called the double electron transition peak or the two-electron satellite line, usually recorded as TES.

[0012] The above measurement method can measure the double electron transition rate of donor bound excitons in various semiconductor materials, and is particularly suitable for semiconductor materials with large exciton binding energy, such as wide bandgap semiconductor materials and two-dimensional materials, specifically including InN, GaN, AlN, BN, ZnO, SiC, diamond (C), Ga2O3, GaP, InSe, InTe, black phosphorus (P), MoS2, MoSe2, WS2, WSe2, etc. The temperature described in each step of the above measurement method refers to the temperature point selected in the temperature range below the temperature of the complete thermal quenching temperature of the bound exciton luminescence peak in the semiconductor material of the research object. These temperature points can fall within the temperature range, and the specific values ​​are not strictly specified. However, there are certain restrictions on the low temperature (LT), that is, the selection of the low temperature needs to meet the requirement that the change in the bound exciton luminescence peak intensity cannot exceed 20% when the low temperature (LT) increases by 10 K. This is because the premise of the above measurement method is that the non-radiative recombination channel is not opened at low temperature, so the selected low temperature needs to be low to a certain extent to meet this restriction, generally the lowest temperature point in the temperature change.

[0013] Optionally, in step 1, the integrated intensity of the donor bound exciton peak at each temperature is extracted And the integrated intensity of the double electron transition peak corresponding to the donor bound exciton The method is:

[0014] Method 1: Directly integrate the donor bound exciton peak and the di-electron transition peak to obtain the integrated intensity of the donor bound exciton peak at each temperature. And the integrated intensity of the double electron transition peak corresponding to the donor bound exciton ;

[0015] Method 2: Use one of the Gauss, Gaussian, Lorentz or Gaussian_LorentzCross functions to perform single peak or multi-peak fitting on the donor bound exciton peak and the di-electron transition peak, and obtain the integrated intensity of the donor bound exciton peak at each temperature from the area parameter in the fitting parameter or the integrated area of ​​the fitting curve. And the integrated intensity of the double electron transition peak corresponding to the donor bound exciton .

[0016] Optionally, in step 2, the lifetime of the donor bound exciton peak at each temperature is extracted The method is:

[0017] Method 1: The monochromatic decay curve at the peak position of the donor-bound exciton peak at different temperatures is fitted using the following expression:

[0018] (1)

[0019] In formula (1), I(t) is the instantaneous intensity of the monochromatic decay curve at the peak of the donor-bound exciton peak at time t, I0 is the offset of the instantaneous intensity, A is the initial intensity, t0 is the offset of time, is the life span. is the lifetime of the donor-bound exciton peak at each temperature .

[0020] Method 2: The monochromatic decay curve at the peak position of the donor-bound exciton peak at different temperatures is fitted using the following expression:

[0021] (2)

[0022] In formula (2), I(t) is the instantaneous intensity of the monochromatic decay curve at the peak of the donor-bound exciton peak at time t, I0 is the offset of the instantaneous intensity, and A i is the initial intensity of the i-th component, t0 is the time offset, is the lifetime of the i-th component. From the fitting parameters A i To determine the dominant component, that is, to determine all A i The largest value among them, assuming A m is the maximum value, then the mth component dominates, and the fitting parameters is the lifetime of the donor-bound exciton peak at each temperature .

[0023] Optionally, the quantum efficiency of the donor-bound exciton peak derived in step 3 is The expression is:

[0024] (3)

[0025] In formula (3), is the integrated intensity of the donor-bound exciton peak at temperature T, and is the integrated intensity of the donor bound exciton peak at low temperature. There are certain restrictions on the low temperature (LT), that is, the selection of the low temperature needs to meet the requirement that the change in the bound exciton luminescence peak intensity cannot exceed 20% when the low temperature (LT) increases by 10 K. This is because the premise of the above measurement method is that the non-radiative recombination channel is not open at low temperature, so the selected low temperature needs to be low to a certain extent to meet this restriction, which is generally the lowest temperature point in the temperature change.

[0026] Equation (3) holds true because the non-radiative recombination rate of donor-bound excitons is very low at low temperatures, and the radiative recombination rate is close to 100%.

[0027] The reasons are explained below.

[0028] On the one hand, the radiative recombination and non-radiative recombination mentioned here are for donor-bound excitons, and the radiative recombination process refers only to the donor-bound exciton peak. The non-radiative recombination process of donor-bound excitons includes thermal activation to free excitons, two-electron transition process and other non-radiative recombination processes. Since what is discussed here is donor-bound excitons, even if there are luminescence peaks corresponding to two-electron transition and free exciton recombination, the thermal activation to free excitons and two-electron transition processes will lead to the weakening of the donor-bound exciton peak, and these processes are classified as non-radiative recombination processes.

[0029] On the other hand, at low temperatures, the non-radiative recombination rate of donor-bound excitons is very low. The donor-bound exciton state is lower in energy than the free exciton state. At low temperatures, the efficiency of thermal activation of donor-bound excitons to free excitons is very low; at low temperatures, the intensity of the double electron transition peak is very weak compared to the donor-bound exciton peak, so the double electron transition rate is also very low; at low temperatures, other non-radiative recombination processes themselves are rarely activated, and donor-bound excitons are relatively localized, making them more difficult to be captured by some non-radiative recombination centers.

[0030] Optionally, in step 3, the radiative recombination lifetime of donor-bound excitons at each temperature is deduced The method is to use the quantum efficiency of the donor-bound exciton peak at each temperature that has been obtained and donor-bound exciton peak lifetime , solve the following system of equations:

[0031] (4)

[0032] In formula (4), is the radiative recombination lifetime of donor-bound excitons at each temperature, is the non-radiative recombination lifetime of donor-bound excitons at each temperature. It can be solved to and .

[0033] Optionally, in step 4, the double electron transition rate of the donor bound exciton at each temperature is obtained The specific calculation process is as follows:

[0034] There are two types of recombination channels for donor-bound excitons in semiconductor materials, radiative recombination channels and non-radiative recombination channels, which correspond to different rates. The donor-bound exciton peak is the result of the radiative recombination of donor-bound excitons through the radiative recombination channel. The integrated intensity of the donor-bound exciton peak is:

[0035] (5)

[0036] In formula (5), N0 is the total number of donor-bound excitons, is the radiative recombination rate of donor-bound excitons at each temperature, is the non-radiative recombination rate of donor-bound excitons at each temperature.

[0037] The di-electron transition is a competitive process of the normal radiative recombination of donor-bound excitons and is a type of non-radiative recombination channel. The integrated intensity of the di-electron transition peak is:

[0038] (6)

[0039] In formula (6), N0 is the total number of donor-bound excitons, is the two-electron transition rate of donor-bound excitons at each temperature, is the radiative recombination rate of donor-bound excitons at each temperature, is the non-radiative recombination rate of donor-bound excitons at each temperature.

[0040] Comparing formula (6) with formula (5), we can get the following relationship:

[0041] (7)

[0042] The radiative recombination rate of donor-bound excitons is the inverse of their radiative recombination lifetime, i.e.

[0043] (8)

[0044] Substituting equation (8) into equation (7), we can obtain the double electron transition rate of donor bound exciton at each temperature: The expression is:

[0045] (9)

[0046] Therefore, the relative intensities of the double electron transition peak and the donor bound exciton peak at different temperatures divided by the radiative recombination lifetime of the donor bound exciton can be used to obtain the double electron transition rate of the donor bound exciton at each temperature. .

[0047] Optionally, the order of step 1 and step 2 of the measurement method can be swapped.

[0048] Beneficial effects: The present invention is based on photoluminescence. The integrated intensity of the donor-bound exciton peak and the di-electron transition peak at each temperature and the radiative recombination lifetime of the donor-bound exciton are measured by temperature-variable steady-state photoluminescence spectrum and time-resolved photoluminescence spectrum. The di-electron transition rate of the donor-bound exciton at each temperature can be deduced using the information extracted from the spectrum line, which effectively solves the problem that the di-electron transition rate of the donor-bound exciton is difficult to measure, and can quickly and accurately obtain the variation law of the di-electron transition rate of the donor-bound exciton with temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] It should be noted that the drawings in the following description are only some embodiments, and these drawings and text descriptions are not intended to limit the conceptual scope of the present invention in any way, but to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments.

[0050] Figure 1 Schematic diagram of donor-bound excitons and their recombination process in semiconductor materials.

[0051] Figure 2 1 is a steady-state photoluminescence spectrum curve of the semiconductor material at different temperatures in the embodiment.

[0052] Figure 3 Reason Figure 2 The integrated intensity of the donor-bound exciton peak extracted at each temperature And the integrated intensity of the double electron transition peak corresponding to the donor bound exciton .

[0053] Figure 4 It is a monochromatic decay curve at the peak position of the donor bound exciton peak of the semiconductor material in the embodiment at different temperatures.

[0054] Figure 5 is the lifetime of the donor bound exciton peak at each temperature extracted in the example And the inferred radiative recombination lifetime and the non-radiative recombination lifetime .

[0055] Figure 6 is the double electron transition rate of donor bound exciton at each temperature deduced in the example .

[0056] Figure 7 The present invention is a flowchart for implementing the method for measuring the double electron transition rate of donor bound excitons in the semiconductor material of the present invention. DETAILED DESCRIPTION

[0057] The present invention is further described in detail below by way of embodiments in conjunction with the accompanying drawings. However, it should be understood that these drawings and textual descriptions are only to further describe the features and advantages of the present invention for those skilled in the art by reference to specific embodiments, and are not intended to limit the scope of the present invention in any way.

[0058] In this embodiment, a method for measuring the double electron transition rate of donor bound excitons in semiconductor materials is provided to solve the problem that it is currently difficult to measure the double electron transition rate of donor bound excitons in semiconductor materials. Figure 1 As shown in the figure, there are two types of recombination channels for donor-bound excitons in semiconductor materials, radiative recombination channels and non-radiative recombination channels, which correspond to different rates. The donor-bound exciton peak is the result of radiative recombination of donor-bound excitons through radiative recombination channels. The double electron transition is a competitive process of the normal radiative recombination of donor-bound excitons and is a type of non-radiative recombination channel.

[0059] See also Figure 7 , the method for measuring the double electron transition rate of donor bound excitons in a semiconductor material, the specific process is:

[0060] Step 1: Use variable temperature steady-state photoluminescence spectroscopy to measure the steady-state photoluminescence spectrum curve of semiconductor material AlN at different temperatures, such as Figure 2 As shown, the donor bound exciton peak and the double electron transition peak are multi-peak fitted using the Gaussian function, and the integrated intensity of the donor bound exciton peak at each temperature is obtained from the area parameter in the fitting parameters. And the integrated intensity of the double electron transition peak corresponding to the donor bound exciton ,like Figure 3 As shown;

[0061] Step 2: Use variable temperature time-resolved photoluminescence spectroscopy to measure the monochromatic decay curve at the peak position of the donor-bound exciton peak of the semiconductor material at different temperatures, such as Figure 4 As shown, the monochromatic decay curves at the peak of the donor-bound exciton peak at different temperatures are fitted using formula (1) to extract the lifetime of the donor-bound exciton peak at each temperature. ; Figure 4 The monochromatic decay curves at the peak of the donor-bound exciton peak at 10K, 30K and 5K are shown in Figure 2. The PL lifetimes extracted are 159 ps, 128 ps and 58 ps respectively;

[0062] Step 3: The integrated intensity of the donor-bound exciton peak obtained in step 1 According to formula (3), we can deduce (where is the integrated intensity of the donor-bound exciton peak at the lowest temperature point 4.5 K) The quantum efficiency of the donor-bound exciton peak , and then the quantum efficiency of the donor-bound exciton peak and the donor-bound exciton peak lifetime obtained in step 2 According to equation (4), the radiative recombination lifetime of donor-bound excitons at different temperatures can be deduced as ,like Figure 5 As shown;

[0063] Step 4: The integrated intensity of the donor-bound exciton peak at each temperature obtained in step 1 , the integrated intensity of the double electron transition peak corresponding to the donor bound exciton And the radiative recombination lifetime of donor-bound excitons at each temperature obtained in step 3 According to formula (9), the double electron transition rate of donor bound excitons at each temperature can be obtained: ,like Figure 6 shown.

[0064] In this embodiment, the measurement method is based on photoluminescence, and the integrated intensity of the donor-bound exciton peak and the double electron transition peak at each temperature and the radiative recombination lifetime of the donor-bound exciton are measured by the temperature-variable steady-state photoluminescence spectrum and the time-resolved photoluminescence spectrum. The double electron transition rate of the donor-bound exciton at each temperature can be deduced by using the information extracted from the spectrum line, which effectively solves the problem that the double electron transition rate of the donor-bound exciton is difficult to measure, and can quickly and accurately obtain the variation law of the double electron transition rate of the donor-bound exciton with temperature. This embodiment shows the excellent beneficial effects of the present invention.

[0065] The present invention is not limited to the above-mentioned embodiments. Anyone should be aware that any structural or step changes made under the enlightenment of the present invention, and any technical solutions that are the same or similar to the present invention, fall within the protection scope of the present invention. The technical parts and structural parts not described in detail in the present invention are all well-known technologies.

Claims

1. A method for measuring the double electron transition rate of donor bound excitons in semiconductor materials, characterized in that: The following steps are involved: Step 1: Use variable temperature steady-state photoluminescence spectroscopy to measure the steady-state photoluminescence spectrum curve of semiconductor materials at different temperatures, and extract the integrated intensity of the donor-bound exciton peak at each temperature And the integrated intensity of the double electron transition peak corresponding to the donor bound exciton ; Step 2: Use variable temperature time-resolved photoluminescence spectroscopy to measure the monochromatic decay curve at the peak of the donor-bound exciton peak of the semiconductor material at different temperatures, and extract the lifetime of the donor-bound exciton peak at each temperature ; Step 3: The integrated intensity of the donor-bound exciton peak obtained in step 1 The quantum efficiency of the donor-bound exciton peak is derived , and then the quantum efficiency of the donor-bound exciton peak and the donor-bound exciton peak lifetime obtained in step 2 The radiative recombination lifetime of donor-bound excitons at different temperatures is deduced ; Step 4: The integrated intensity of the donor-bound exciton peak at each temperature obtained in step 1 , the integrated intensity of the double electron transition peak corresponding to the donor bound exciton And the radiative recombination lifetime of donor-bound excitons at each temperature obtained in step 3 According to formula (9), the double electron transition rate of donor bound excitons at each temperature is calculated as : (9)。 2. The measuring method according to claim 1, characterized in that: The semiconductor material is a wide bandgap semiconductor material or a two-dimensional material; the temperature refers to a temperature point selected in a temperature range below the complete thermal quenching temperature of the bound exciton luminescence peak in the semiconductor material.

3. The measuring method according to claim 1, characterized in that: In step 1, one of the following methods is used to extract the integrated intensity of the donor bound exciton peak at each temperature: And the integrated intensity of the double electron transition peak corresponding to the donor bound exciton : Method 1: Directly integrate the donor bound exciton peak and the di-electron transition peak to obtain the integrated intensity of the donor bound exciton peak at each temperature. And the integrated intensity of the double electron transition peak corresponding to the donor bound exciton ; Method 2: Use one of the Gauss, Gaussian, Lorentz or Gaussian_LorentzCross functions to perform single peak or multi-peak fitting on the donor bound exciton peak and the di-electron transition peak, and obtain the integrated intensity of the donor bound exciton peak at each temperature from the area parameter in the fitting parameter or the integrated area of ​​the fitting curve. And the integrated intensity of the double electron transition peak corresponding to the donor bound exciton .

4. The measuring method according to claim 1, characterized in that: In step 2, one of the following methods is used to extract the lifetime of the donor bound exciton peak at each temperature: : Method 1: The monochromatic decay curve at the peak position of the donor-bound exciton peak at different temperatures is fitted using formula (1): (1) In formula (1), I(t) is the instantaneous intensity of the monochromatic decay curve at the peak of the donor-bound exciton peak at time t, I0 is the offset of the instantaneous intensity, A is the initial intensity, t0 is the offset of time, is the life span; is the lifetime of the donor-bound exciton peak at each temperature ; Method 2: The monochromatic decay curves at the peak position of the donor-bound exciton peak at different temperatures are fitted using formula (2): (2) In formula (2), I(t) is the instantaneous intensity of the monochromatic decay curve at the peak of the donor-bound exciton peak at time t, I0 is the offset of the instantaneous intensity, and A i is the initial intensity of the i-th component, t0 is the time offset, is the lifetime of the i-th component; From the fitting parameters A i To determine the dominant component, that is, to determine all A i The largest value among them, assuming A m is the maximum value, then the mth component dominates, and the fitting parameters is the lifetime of the donor-bound exciton peak at each temperature .

5. The measuring method according to claim 1, characterized in that: In step 3, the quantum efficiency of the donor-bound exciton peak is deduced according to equation (3): : (3) In formula (3), is the integrated intensity of the donor-bound exciton peak at temperature T, and is the integrated intensity of the donor bound exciton peak at low temperature, and the selection of the low temperature needs to satisfy the requirement that the change in the bound exciton luminescence peak intensity cannot exceed 20% when the low temperature increases by 10 K.

6. The measuring method according to claim 5, characterized in that: In step 3, the radiative recombination lifetime of donor-bound excitons at each temperature is deduced as The method is to use the quantum efficiency of the donor-bound exciton peak at each temperature that has been obtained and donor-bound exciton peak lifetime , solve equation (4) and get and : (4) In formula (4), is the radiative recombination lifetime of donor-bound excitons at each temperature, is the non-radiative recombination lifetime of donor-bound excitons at various temperatures.

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