Atomic-level observation method for electron beam irradiation-induced micro-defect repair in GaN materials

Abstract

This invention provides an atomic-level observation method for electron beam irradiation-induced microscopic defect repair in GaN materials, belonging to the fields of materials science and electron microscopy. This method utilizes aberration-corrected transmission electron microscopy (AC-TEM) combined with focused ion beam (FIB) sample preparation and precise electron beam irradiation control to achieve atomic-level real-time observation of the dynamic repair process of microscopic defects in GaN materials. Specific steps include: selecting the GaN sample type and determining experimental parameters; preparing the sample using FIB; mounting the sample in the AC-TEM sample holder and adjusting it to the target observation crystal plane; optimizing AC-TEM parameters to ensure clear atomic images; generating nanopores through FIB irradiation and observing their repair process in real time; and using image analysis software to quantitatively analyze the defect repair dynamics. This invention solves the problem of traditional methods being unable to capture the dynamic defect repair process in real time, providing important experimental means and theoretical support for studying the defect evolution mechanism and performance optimization of GaN materials.

Description

Technical Field

[0001] This invention belongs to the fields of materials science and electron microscopy, specifically relating to an atomic-level observation method for electron beam irradiation-induced microscopic defect repair in GaN materials. Background Technology

[0002] GaN, as a third-generation wide-bandgap semiconductor material, possesses characteristics such as a wide bandgap, high breakdown electric field, high thermal conductivity, and high carrier mobility, making it promising for applications in aerospace, nuclear radiation detection, and other fields. However, when applied in these fields, it is inevitably subject to radiation damage, leading to performance degradation and even functional failure. For example, high-energy particle irradiation can induce microscopic defects such as point defects, dislocations, and latent tracks in GaN materials, severely affecting device reliability and lifespan. Furthermore, ion implantation technology, a key method for achieving junction termination and doping in device fabrication, faces significant challenges in GaN applications. On the one hand, ion implantation introduces numerous defects, causing damage to the material's crystal structure and consequently affecting device reliability and performance stability. On the other hand, due to the compensating effect of defects on carriers, implanted impurity atoms are difficult to activate effectively, severely restricting the electrical performance and functional realization of GaN devices. Therefore, achieving defect repair in GaN materials and real-time monitoring of these defects is of great significance.

[0003] In recent years, with the development of aberration-corrected transmission electron microscopy (AC-TEM) technology, real-time observation at atomic resolution has become possible. AC-TEM can not only provide high-resolution atomic images but also repair defects in GaN, providing a powerful tool for studying the evolution of its microstructure. However, current methods for atomic-level observation of the dynamic repair process of GaN materials under electron beam irradiation still have the following problems: 1. The lack of a systematic experimental protocol makes it difficult to standardize the entire process from sample preparation to real-time observation; 2. During electron beam irradiation, sample drift and imprecise control of irradiation parameters affect the accuracy of observation results.

[0004] To address the aforementioned issues, an atomic-level observation method based on AC-TEM is needed for the dynamic repair process of microscopic defects in GaN materials by electron beam irradiation. This method would provide an important experimental tool for studying the defect evolution mechanism and performance optimization of GaN materials. Summary of the Invention

[0005] To achieve atomic-level observation of defect repair in GaN materials, this invention provides an atomic-level observation method for electron beam irradiation-induced microscopic defect repair in GaN materials. This method enables high-precision real-time observation of the dynamic evolution process of electron beam irradiation-induced defects at the atomic scale, solving the problem that traditional methods are difficult to capture the dynamic behavior of defect repair. It provides important experimental means and theoretical support for the study of defect repair mechanisms and performance optimization of GaN materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An atomic-level observation method for electron beam irradiation-induced microdefect repair in GaN materials includes the following steps: Step 1: Select the type of GaN material sample to be tested, determine the crystal plane to be observed at the atomic level, and select the AC-TEM model and electron beam energy; Step 2: Based on the selected GaN material sample type, determine the crystal orientation of the GaN bulk material, select the positioning edge, and prepare the experimental GaN sample using focused ion beam (FIB) technology; Step 3: Install the FIB-prepared sample into the AC-TEM sample holder and insert the sample holder into the AC-TEM. Step 4: Adjust the tilt angle of the sample rod so that the GaN sample reaches the target crystal plane for observation; Step 5: Adjust AC-TEM mode to scanning transmission electron microscopy (STEM) mode, set the current, test and record the current intensity through the fluorescent screen; optimize electron microscope parameters in STEM mode to ensure that a clear atomic image can be obtained and that the drift distance of the sample rod does not exceed 3 columns of atoms within 30 seconds. Step 6: Adjust the AC-TEM mode to the focusing mode, continuously irradiate the GaN sample with an electron beam for no more than 2 minutes, and record the irradiation time; Step 7: Confirm that the electron beam irradiation in Step 6 has produced nanopores in low-magnification STEM mode; set the electron beam dwell time and resolution parameters, and gradually increase the magnification near the pores until the predetermined magnification is reached; adjust the electron microscope parameters to ensure that clear atomic images can be observed. Step 8: Activate the recording mode, move the hole to the center of the AC-TEM field of view, and observe and record the atomic-level repair process in real time; Step 9: After the hole is completely repaired, stop recording and turn off the AC-TEM electron beam to complete the atomic-level observation of the dynamic process of microscopic defect repair.

[0007] Finally, based on the atomic-level observations of the recorded repair process, image analysis software was used to perform quantitative analysis of the defect repair dynamics.

[0008] Furthermore, in step one, the AC-TEM electron beam energy generally does not exceed 300 keV. GaN material sample types can be classified according to carrier concentration into n-type GaN, semi-insulating GaN, and p-type GaN; they can also be classified according to substrate type into self-supporting GaN, GaN on Si, GaN on sapphire, GaN on diamond, and GaN on silicon carbide, etc.

[0009] Furthermore, in step two, in order to reduce the influence of stress stripes generated during FIB sample preparation and irradiation on the sample, the size of the GaN sample prepared by FIB should be as small as possible, provided that the experimental requirements are met. Generally, the sample length should not exceed 10 μm, the width should not exceed 6 μm, and the thickness should not exceed 100 nm.

[0010] Furthermore, in step four, the sample crystal plane is determined by the diffraction spots. If the sample crystal plane is consistent with the target observed crystal plane, the tilt angle of the sample rod at this time is recorded. If the sample crystal plane is inconsistent with the target observed crystal plane, the sample is rotated to be consistent with the target observed crystal plane according to the Kikuchi pole characteristics of the sample, and the tilt angle of the sample rod at this time is recorded.

[0011] Furthermore, in step five, the criterion for determining that the sample rod hardly drifts is: within 30 seconds, the atomic image drift distance does not exceed 3 columns of atoms.

[0012] Furthermore, in step six, the electron beam irradiation time in focusing mode does not exceed 2 minutes.

[0013] Furthermore, in step seven, the electron beam dwell time is set to no more than 20 μs, and the resolution to no more than 2048×2048. The predetermined magnification is typically 5~50 MHz.

[0014] This invention utilizes AC-TEM technology, through optimized sample preparation, precise control of irradiation parameters, and real-time video recording, to achieve high-precision real-time atomic-level observation of the dynamic repair process of microscopic defects in GaN materials under electron beam irradiation. This provides an important experimental method for studying the defect repair evolution mechanism and performance optimization of GaN materials. Compared with existing technologies, this invention has the following advantages: 1. Achieving atomic-level real-time observation to capture the dynamic defect repair process. Traditional methods typically only allow observation of microstructural changes in materials through offline testing after irradiation experiments, failing to capture the dynamic evolution of defects in real time. This invention utilizes AC-TEM technology, combined with precise electron beam irradiation control and real-time video recording, to achieve atomic-level real-time observation of the micro-defect repair process in GaN materials.

[0015] 2. This invention provides crucial technical support for research on defect repair mechanisms. Through high-precision real-time observation and data analysis, it enables quantitative research on defect repair speed and other parameters, providing important experimental evidence for theoretical research on defect repair mechanisms. Furthermore, this method has significant scientific and practical value for developing efficient defect repair technologies and filling the gap in dynamic repair observation technology for microscopic defects in GaN materials. Attached Figure Description

[0016] Figure 1 This is a flowchart of an atomic-level observation method for electron beam irradiation-induced micro-defect repair in GaN materials, as described in this embodiment of the invention.

[0017] Figure 2 Images of the nanopore preparation process in an embodiment of the present invention are shown, where (a) and (b) are images before irradiation and after 30 s of irradiation, respectively.

[0018] Figure 3 Images of the nanopore repair process in an embodiment of the present invention are shown, where (a), (b), (c), and (d) are images of the repair process at 1s, 50s, 720s, and 900s, respectively. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the embodiments are merely used to explain the technical principles of the present invention and describe specific implementation processes, and are not intended to limit the scope of protection of the present invention.

[0020] This invention proposes an atomic-level observation method for electron beam irradiation-induced micro-defect repair in GaN materials. This method enables real-time atomic-level observation of the micro-defect repair process in GaN materials, providing important experimental support for the study of defect repair in GaN materials. The following section combines... Figure 1 The atomic-level observation method for repairing microscopic defects according to the present invention is described below, with the specific steps as follows: Step 1: Select self-supporting n-type GaN as the GaN sample to be tested, determine the crystal plane for atomic-level observation as [-2 1 1 0], and select the aberration-corrected transmission electron microscope (AC-TEM) model as JEM-ARM300F2 with an electron beam energy of 300 keV. Step 2: Based on the selected GaN sample type, determine the crystal orientation of the GaN bulk material, select the positioning edge, and prepare the experimental GaN sample using focused ion beam (FIB) technology; Step 3: Install the FIB-prepared sample into the AC-TEM sample holder and insert the sample holder into the AC-TEM. Step 4: Adjust the tilt angle of the sample rod and fine-tune the sample band axis to achieve the target crystal plane for observation; Step 5: Adjust AC-TEM to STEM mode, increase the current and test and record the current intensity as 84 pA through the fluorescent screen; optimize the electron microscope parameters in STEM mode to ensure that a clear atomic image can be obtained and that the drift distance of the sample rod does not exceed 3 columns of atoms within 30 seconds. Step Six: Adjust the AC-TEM mode to focused mode, continuously irradiate the sample for 30 seconds, and record the irradiation time. This will create nanopores on the sample. Figure 2 As shown; Step 7: Confirm that the electron beam irradiation has produced nanopores in low-magnification STEM mode; set the electron beam dwell time to 2 μs and the resolution to 1024×1024, and gradually increase the magnification near the pores until the predetermined magnification is reached; adjust the electron microscope parameters to ensure that clear atomic images can be observed. Step 8: Activate recording mode, move the hole to the center of the AC-TEM field of view, and observe and record the atomic-level repair process in real time, such as... Figure 3 As shown; Step 9: After the hole is completely repaired, stop recording and turn off the AC-TEM electron beam to complete the atomic-level observation of the dynamic process of microscopic defect repair. Step 10: Use the image analysis software ImageJ to perform quantitative analysis on the defect repair dynamics.

Claims

1. An atomic-level observation method for electron beam irradiation-induced micro-defect repair in GaN materials, comprising the following steps: 1) Select the type of GaN material sample to be tested, determine the crystal plane to be observed at the atomic level, and select the AC-TEM model and electron beam energy; 2) Based on the type of GaN material sample, determine the crystal orientation of the GaN bulk material, select the positioning edge, and use focused ion beam to prepare GaN samples for the experiment; 3) Mount the GaN sample into the AC-TEM sample holder and insert the sample holder into the AC-TEM; 4) Adjust the tilt angle of the sample rod so that the GaN sample reaches the target crystal plane for observation; 5) Adjust the AC-TEM mode to STEM mode, set the current, test and record the current intensity through the fluorescent screen; optimize the electron microscope parameters in STEM mode to ensure that a clear atomic image can be obtained and that the drift distance of the sample rod does not exceed 3 columns of atoms within 30 seconds. 6) Adjust the AC-TEM mode to the focusing mode, continuously irradiate the GaN sample with an electron beam for no more than 2 minutes, and record the irradiation time; 7) Confirm that the electron beam irradiation in step 6) has generated nanopores in low magnification STEM mode; set the electron beam dwell time and resolution parameters, and gradually increase the magnification near the pores until the predetermined magnification is reached; Adjust the electron microscope parameters to ensure that clear atomic images can be observed; 8) Activate the recording mode, move the hole to the center of the AC-TEM field of view, and observe and record the atomic-level repair process in real time; 9) After the hole is completely repaired, stop recording and turn off the AC-TEM electron beam to complete the atomic-level observation of the dynamic process of microscopic defect repair.

2. The atomic-level observation method as described in claim 1, characterized in that, Based on the atomic-level observations of the recorded repair process, image analysis software was used to perform quantitative analysis of the defect repair dynamics.

3. The atomic-level observation method as described in claim 1, characterized in that, In step 1), the AC-TEM electron beam energy is selected to be no more than 300 keV; the GaN material sample type is classified according to carrier concentration or substrate type.

4. The atomic-level observation method as described in claim 1, characterized in that, Step 2) The GaN sample prepared has a length of no more than 10 μm, a width of no more than 6 μm, and a thickness of no more than 100 nm.

5. The atomic-level observation method as described in claim 1, characterized in that, In step 4), the sample crystal plane is determined by the diffraction spots. If the sample crystal plane is consistent with the target observed crystal plane, the sample rod tilt angle is recorded at this time. If the sample crystal plane is not consistent with the target observation crystal plane, then according to the Kikuchi polarity of the sample, rotate the sample to be consistent with the target observation crystal plane, and record the tilt angle of the sample rod at this time.

6. The atomic-level observation method as described in claim 1, characterized in that, In step 7), the electron beam dwell time is set to be no more than 20 μs and the resolution to be no more than 2048×2048.

7. The atomic-level observation method as described in claim 1, characterized in that, The predetermined magnification mentioned in step 7) is 5~50 M.

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