A characterization method for detecting p-type group iii nitride activation effect
By preparing a metal electrode layer on the surface of p-type group III nitrides and connecting it to a Kelvin probe force microscope, the activation effect of p-type group III nitrides can be detected by utilizing the surface potential difference. This solves the problem of inaccurate test results in complex epitaxial structures and achieves precise measurement of activation effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANCHANG UNIV
- Filing Date
- 2023-03-09
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies struggle to accurately detect the activation effect of p-type group III nitrides, especially in complex epitaxial structures where the influence of other epitaxial layers leads to inaccurate test results.
A metal electrode layer was prepared on the surface of a p-type group III nitride using a Kelvin probe force microscope to form an ohmic contact, which was then electrically connected to the sample stage of the probe force microscope. The activation effect was determined by the surface potential difference, and quantitative characterization was performed using a Hall effect test system.
This method enables precise measurement of the activation effect of p-type group III nitrides, reduces the influence of other epitaxial layers, and is simple and effective.
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Figure CN116298400B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor material testing technology, and in particular to a characterization method for detecting the activation effect of p-type group III nitrides. Background Technology
[0002] Group III nitrides, represented by GaN, have gradually become a new generation of lighting sources due to their controllable panchromatic spectral bandgap and excellent physicochemical properties, and have shown broad prospects in power electronic devices.
[0003] The rapid development of group III nitride materials and devices is mainly due to the solving of two major challenges. The first is obtaining high-quality GaN-based epitaxial layers on heterogeneous substrates, and the second is obtaining p-type GaN materials with high hole concentrations. For the first challenge, current research has made breakthroughs in growing GaN-based epitaxial layers on sapphire, silicon carbide, and silicon substrates, meeting the requirements for commercial production. However, for the second challenge, in 1989, Akasaki obtained p-type GaN with high hole concentrations using low-energy electron irradiation (LEEBI), realizing the fabrication of GaN-based PN junction LED devices. In 1992, Nakamura achieved hole activation by annealing Mg-doped GaN with nitrogen (N2). Although commercial production has been achieved, the hole activation rate of p-type GaN remains relatively low in GaN-based devices to date, limiting the improvement of device performance.
[0004] In recent years, the rapid development of ultraviolet and deep ultraviolet LEDs and wide bandgap power electronic devices has brought p-type AlGaN to the attention of research institutions and industries. However, the activation of p-type AlGaN is more difficult.
[0005] There are three main reasons why p-type III nitrides are difficult to activate: First, the Mg acceptor has a deep energy level of approximately 170 meV, and the ionization rate of Mg at room temperature is only about 1%. Second, hydrogen is required as a carrier gas when growing Mg-doped p-type III nitride films. Hydrogen forms complexes with the Mg atoms incorporated into the p-type III nitride, thus passivating the Mg acceptor and significantly increasing its activation energy. Third, the intrinsic nitrogen vacancies in p-type III nitrides also self-compensate for the Mg acceptor, further reducing the effective hole concentration. Therefore, even with a high concentration of Mg atoms, the final activated hole concentration in Mg-doped p-type III nitrides is very low. This problem severely restricts the application and development of p-type III nitride materials and devices. This places higher technical demands on the activation of p-type III nitrides and also presents challenges to the characterization of the activation effect.
[0006] Therefore, finding an effective and convenient method to accurately detect the activation effect of p-type III nitrides is of great significance for studying p-type III nitride activation technology. Currently, the main method for testing the activation effect of p-type III nitrides is the Hall effect test: the Hall effect test results show the carrier concentration, and the activation effect of p-type III nitrides is judged by comparing the carrier concentration. However, for complex epitaxial structures, such as complete LED epitaxial structures, including the substrate, n-type III nitride, active region, and p-type III nitride, when performing Hall effect tests on LED epitaxial structures, all epitaxial layers other than the p-type III nitride significantly affect the test results, making it difficult to accurately reflect the actual carrier concentration after p-type III nitride activation. Summary of the Invention
[0007] The purpose of this invention is to provide a convenient, accurate, simple and effective characterization method for detecting the activation effect of p-type group III nitrides.
[0008] The objective of this invention is achieved as follows:
[0009] A characterization method for detecting the activation effect of p-type group III nitrides, characterized by the following steps:
[0010] S1. Prepare a metal electrode layer on the surface of the epitaxial wafer to be tested, which has a p-type group III nitride surface, to obtain the sample to be tested;
[0011] S2. Conductive connection is made between the metal electrode layer on the surface of the sample to be tested and the sample stage of the Kelvin probe force microscope.
[0012] S3. The surface potential of the p-type group III nitride and the metal electrode layer on the surface of the sample to be tested is measured simultaneously using a Kelvin probe force microscope. The activation effect is judged based on the surface potential difference between the p-type group III nitride and the metal electrode layer, and the characterization is completed.
[0013] Optionally, the group III nitride is one of GaN, AlN, InN, AlGaN, InGaN, AlInN, and AlInGaN.
[0014] Optionally, the method for preparing the metal electrode layer in step S1 is vapor deposition, sputtering, imprinting, or electroplating.
[0015] Optionally, the material of the metal electrode layer in step S1 is Ni / Ag, Ni / Au, Ni / Pt / Au, or Ni / Pd / Au.
[0016] Optionally, the height of the metal electrode layer in step S1 is 1 nm to 200 nm, and the width of the metal electrode layer is 2 μm to 100 μm.
[0017] Optionally, the conductive connection in step S2 can be a conductive silver paste connection, a conductive tape connection, or a conductive clamp connection.
[0018] Optionally, the following steps may also be included:
[0019] S4. Combined with the calibration of the standard sample, the surface potential results obtained in step S3 are processed to quantitatively characterize the activation effect of p-type group III nitrides.
[0020] Optionally, the standard sample calibration in step S4 is performed by testing the standard sample using a Kelvin probe force microscope and a Hall effect test system, and establishing a correspondence between surface potential and carrier concentration. The quantitative characterization method is to convert the surface potential result obtained in step S3 into a specific carrier concentration based on the established correspondence between surface potential and carrier concentration, and to obtain the specific activation effect of the p-type group III nitride by comparing the specific carrier concentration with the doping concentration of the p-type group III nitride, thus completing the characterization.
[0021] Optionally, the epitaxial wafer to be tested, which is a p-type group III nitride, in step S1, further includes, from bottom to top, at least one of a substrate, an n-type group III nitride layer, or an active layer.
[0022] The beneficial effects of this invention are as follows:
[0023] This invention, based on Kelvin probe force microscopy, establishes an ohmic contact by fabricating a metal electrode layer on the surface of p-type group III nitrides and electrically connecting the metal electrode layer to the sample stage of the Kelvin probe force microscope. This reduces the influence of other epitaxial layers besides the p-type group III nitrides on the test results. The surface potential is calculated based on the difference between the surface potential of the p-type group III nitrides and the metal electrode layer, or by combining this with a Hall effect test system. This allows for a relatively accurate measurement of the activation effect of p-type group III nitrides. This method is simple, rapid, and effective, accurately measuring the change in surface potential of p-type group III nitrides before and after activation, and will play a significant role in the study of p-type group III nitride activation methods. Attached Figure Description
[0024] Figure 1 This is a flowchart of the method for characterizing the activation effect of p-type III nitrides according to the present invention;
[0025] Figure 2 This is a schematic diagram of the system structure for measuring the surface potential of a sample using a Kelvin probe force microscope. 1-Sample stage, 2-Sample to be measured, 3-External circuit, 4-Conductive probe, 5-Cantilever.
[0026] Figure 3 This is a schematic diagram of the structure of the test samples in Embodiments 1 and 3 of the present invention, 6-substrate, 7-n-type layer, 8-active layer, 9-p-type layer, 10-metal electrode layer, 11-epitaxy wafer under test;
[0027] Figure 4 This is a top view schematic diagram of the test samples in Embodiments 1, 2 and 3 of the present invention, 9-p-type layer, 10-metal electrode layer, 12-test area;
[0028] Figure 5 These are curves showing the relationship between the relative surface potential of the NiAg metal electrode layer in Embodiment 1 of the present invention and the relative surface potential of the p-type GaN layer after activation, and the p-type GaN layer without activation and with position.
[0029] Figure 6 This is a schematic diagram of the structure of the sample to be tested in Embodiment 2 of the present invention, 6-substrate, 9-p-type layer, 10-metal electrode layer. Detailed Implementation
[0030] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.
[0031] Reference Figure 1 The above is a flowchart of the characterization method for detecting the activation effect of p-type group III nitrides according to the present invention. The present invention provides the following embodiments:
[0032] Example 1
[0033] Specifically, Embodiment 1 discloses a characterization method for detecting the activation effect of p-type GaN based on Kelvin probe force microscopy. In this embodiment, the conductive coating on the surface of the conductive probe is PtIr. The implementation steps of this characterization method are as follows:
[0034] S1. A NiAg metal electrode layer 10 with a height of 100 nm and a width of 30 μm is prepared on the surface of the epitaxial wafer 11 to be tested, which has a p-type GaN surface, using a vapor deposition method. The Ni metal component in the NiAg metal electrode layer 10 can ensure good ohmic contact with the p-type layer 9, thus obtaining the test sample 2. The structure of the test sample 2 is as follows. Figure 3 As shown, the sample under test, from bottom to top, consists of a Si substrate (6), an n-type GaN layer (7), an InGaN / GaN active layer (8), a p-type GaN layer (9), and a NiAg metal electrode layer (10).
[0035] S2. Fix the sample 2 to be tested on the sample stage 1 of the Kelvin probe force microscope, and use conductive silver paste to form a conductive connection between the NiAg metal electrode layer 10 on the surface of the sample 2 and the sample stage 1 of the Kelvin probe force microscope, to obtain the following result: Figure 2 The system structure shown is a Kelvin probe force microscope for measuring the surface potential of a sample. The sample stage 1 of the Kelvin probe force microscope is electrically connected to the cantilever 5 and the conductive probe 4 with a PtIr conductive coating via an external circuit 3. Therefore, a good conductive loop exists between the NiAg metal electrode layer 10 on the surface of the sample 2 and the conductive probe 4, ensuring that the surface potential of the NiAg metal electrode layer 10 is not interfered with by other factors during testing. Furthermore, the NiAg metal electrode layer 10 and the p-type GaN layer 9 on the surface of the epitaxial wafer 11 have good ohmic contact. The p-type GaN layer 9 on the surface of wafer 11 and the epitaxial structure InGaN / GaN active layer 8 and n-type GaN layer 7 in the epitaxial wafer 11 under test are all semiconductor contacts. Therefore, when measuring the surface potential of the p-type GaN layer 9 on the surface of the epitaxial wafer 11 under test, the conductive circuit between the surface of the p-type GaN layer 9 and the conductive probe 4 will choose to pass through the NiAg metal electrode layer 10, instead of the InGaN / GaN active layer 8, n-type GaN layer 7 and Si substrate 6 under the p-type GaN layer 9, thus eliminating the test influence caused by other epitaxial layers other than the p-type GaN layer 9.
[0036] S3. Using a Kelvin probe force microscope, the surface potential of the p-type GaN layer 9 and the NiAg metal electrode layer 10 on the surface of the sample 2 is simultaneously measured. The conductive probe 4 is lowered to a height of 150 μm from the surface of the sample 2. Figure 4 The top view of the p-type GaN layer 9 under test shows that the conductive probe 4 scans the testing area 12, with a scanning range of 50 μm × 50 μm. An external circuit 3 applies a voltage between the conductive tip 4 and the sample 2 under test to counteract the surface potential of the testing area 12, minimizing the amplitude of the conductive probe 4. When the amplitude is minimized, the surface potential of the testing area 12 is equal to the applied voltage. Thus, the surface potentials of the p-type GaN layer 9 and the NiAg metal electrode layer 10 on the surface of the sample 2 under test are obtained in the testing area 12. The surface potential of the NiAg metal electrode layer 10 is set to 0. By comparing the difference between the surface potential of the p-type GaN layer 9 and the surface potential of the NiAg metal electrode layer 10, the activation effect of the p-type GaN layer 9 is characterized. Figure 5 The figure shows the relationship curves between the relative surface potential of the NiAg metal electrode layer 10 and the relative surface potential of the p-type GaN layer 9 after activation, and the p-type GaN layer before and after activation, as well as the position. The difference between the relative surface potential of the NiAg metal electrode layer 10 and the relative surface potential of the p-type GaN layer 9 under test on the same curve reflects the activation effect. The larger the difference, the better the activation effect, thus completing the characterization.
[0037] Example 2
[0038] Specifically, this embodiment 2 discloses a characterization method for detecting the activation effect of p-type GaN based on Kelvin probe force microscopy. In this embodiment, the conductive coating on the surface of the conductive probe 4 is PtIr. Steps S2 and S3 of this characterization method are the same as in embodiment 1. The steps that differ from those in embodiment 1 are:
[0039] S1. A NiAg metal electrode layer 10 with a height of 120 nm and a width of 30 μm is prepared on the surface of the epitaxial wafer 11 to be tested, which has a p-type GaN layer 9 on its surface, using a vapor deposition method. The Ni metal component in the NiAg metal electrode layer 10 can ensure good ohmic contact with the p-type GaN layer 9, thus obtaining the test sample 2. The structure of the test sample 2 is as follows. Figure 6 As shown, the sample under test 2 consists of a Si substrate 6, a p-type GaN layer 9, and a NiAg metal electrode layer 10 from bottom to top.
[0040] S4. The carrier concentration of the p-type GaN epitaxial wafer to be tested in step S1 is measured using Hall effect testing, and a correspondence is established with the surface potential of the p-type GaN layer 9 to be tested obtained in step S3. Based on the correspondence between the carrier concentration and the surface potential, the relative surface potential of the p-type GaN layer 9 to be tested is converted to carrier concentration. The specific activation effect of the p-type GaN layer 9 is obtained based on the ratio of the specific carrier concentration to the doping concentration in the p-type GaN layer 9, thus completing the characterization.
[0041] Example 3
[0042] Specifically, this embodiment 3 discloses a characterization method for detecting the activation effect of p-type AlGaN based on Kelvin probe force microscopy. In this embodiment, the conductive coating on the surface of the conductive probe 4 is PtIr. Steps S2 and S3 of this characterization method are the same as in embodiment 1. The steps that differ from those in embodiment 1 are:
[0043] S1. A NiAg metal electrode layer 10 with a height of 100 nm and a width of 30 μm is prepared on the surface of the epitaxial wafer 11 to be tested, which has a p-type AlGaN layer 9 on its surface, using a vapor deposition method. The Ni metal component in the NiAg metal electrode layer 10 can ensure good ohmic contact with the p-type AlGaN layer 9, thus obtaining the test sample 2. The structure of the test sample 2 is as follows. Figure 3 As shown, the sample under test 2 consists of, from bottom to top, a Si substrate 6, an n-type AlGaN layer 7, an InGaN / GaN active layer 8, a p-type AlGaN layer 9, and a NiAg metal electrode layer 10.
[0044] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.
Claims
1. A characterization method for detecting the activation effect of p-type group III nitrides, characterized in that: Includes the following steps: S1. A metal electrode layer is prepared on the surface of the epitaxial wafer to be tested, which is a p-type group III nitride, to obtain the sample to be tested; the metal electrode layer forms an ohmic contact with the p-type group III nitride. S2. Conductive connection is made between the metal electrode layer on the surface of the sample to be tested and the sample stage of the Kelvin probe force microscope. S3. The surface potential of the p-type group III nitride and the metal electrode layer on the surface of the sample to be tested is measured simultaneously using a Kelvin probe force microscope. The activation effect is judged based on the surface potential difference between the p-type group III nitride and the metal electrode layer, and the characterization is completed.
2. The characterization method for detecting the activation effect of p-type group III nitrides according to claim 1, characterized in that: The group III nitride is one of GaN, AlN, InN, AlGaN, InGaN, AlInN, and AlInGaN.
3. The characterization method for detecting the activation effect of p-type group III nitrides according to claim 1, characterized in that: The method for preparing the metal electrode layer in step S1 is vapor deposition, sputtering, imprinting, or electroplating.
4. The characterization method for detecting the activation effect of p-type group III nitrides according to claim 1, characterized in that: The material of the metal electrode layer in step S1 is Ni / Ag, Ni / Au, Ni / Pt / Au, or Ni / Pd / Au.
5. The characterization method for detecting the activation effect of p-type group III nitrides according to claim 1, characterized in that: The height of the metal electrode layer in step S1 is 1 nm to 200 nm, and the width of the metal electrode layer is 2 μm to 100 μm.
6. The characterization method for detecting the activation effect of p-type group III nitrides according to claim 1, characterized in that: The conductive connection mentioned in step S2 is a conductive silver paste connection, a conductive tape connection, or a conductive clamp connection.
7. The characterization method for detecting the activation effect of p-type group III nitrides according to claim 1, characterized in that: It may also include the following steps: S4, combining the calibration of the standard sample, processing the surface potential results obtained in step S3, and quantitatively characterizing the activation effect of p-type group III nitrides.
8. The characterization method for detecting the activation effect of p-type group III nitrides according to claim 7, characterized in that: The standard sample calibration in step S4 involves testing the standard sample using a Kelvin probe force microscope and a Hall effect test system, respectively, and establishing a correspondence between surface potential and carrier concentration. The quantitative characterization method involves converting the surface potential result obtained in step S3 into a specific carrier concentration based on the established correspondence between surface potential and carrier concentration, and comparing the specific carrier concentration with the doping concentration of p-type group III nitrides to obtain the specific activation effect of p-type group III nitrides, thus completing the characterization.
9. The characterization method for detecting the activation effect of p-type group III nitrides according to claim 1, characterized in that: The epitaxial wafer to be tested, which is a p-type group III nitride in step S1, further includes, from bottom to top, at least one of a substrate, an n-type group III nitride layer, or an active layer.