Особенности спектрально-разрешенной термолюминесценции в облученных микрокристаллах нитрида алюминия
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-01-01 |
| Journal | Журнал технической физики |
| Authors | Д.М. Спиридонов, Д.В. Чайкин, Н.А. Мартемьянов, А.С. Вохминцев, И.А. Вайнштейн |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This study investigates the photoluminescence (PL) and spectrally-resolved thermoluminescence (TL) properties of novel, cation-deficient submicron Aluminum Nitride (AlN) crystals synthesized via a unique gas-phase method.
- Material Focus: Submicron AlN crystals (0.1-2.0 µm hexagonal prisms) exhibiting cation deficiency (Al:N = 0.9:1) and high oxygen (1.6 at.%) and silicon (0.5 at.%) impurity content.
- Synthesis Method: Novel gas-phase synthesis utilizing liquid aluminum, gaseous AlF3, and NH3, offering a potential pathway for high-quality crystal formation.
- Luminescence Peaks: PL and TL spectra are dominated by a broad emission peak centered around 2.98 eV (approximately 420 nm).
- Defect Identification (Emission): The primary emission (3.04 eV component) is attributed to electronic transitions involving aluminum vacancies (VAl) and oxygen-vacancy complexes (VAl-ON).
- Trapping Centers (TL): A strong, single TL peak is observed at 345 K, confirming the presence of stable charge carrier traps.
- Trap Characterization: These traps are identified as nitrogen vacancies (VN) with a low activation energy (EA) of 0.45 eV.
- Kinetic Behavior: The TL process follows high-order kinetics (b ≈ 2.2), indicating a significant probability of charge carrier retrapping into the VN centers.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Crystal Phase | Wurtzite (P63mc) | N/A | Single crystalline phase of AlN powder. |
| Lattice Parameter (a) | 3.1117 | Angstrom | Hexagonal lattice constant. |
| Lattice Parameter (c) | 4.9794 | Angstrom | Hexagonal lattice constant. |
| Particle Size Range | 0.1 - 2.0 | µm | Characteristic size of hexagonal prisms. |
| Stoichiometry (Al:N) | 0.9 : 1 | N/A | Cation-deficient structure. |
| Oxygen Impurity | 1.6 | at.% | Primary impurity concentration. |
| Silicon Impurity | 0.5 | at.% | Secondary impurity concentration. |
| PL Excitation Wavelength | 265 | nm | UV excitation source used for PL. |
| Dominant TL Peak Temperature (Tmax) | 343 ± 5 | K | Temperature of the main thermoluminescence peak. |
| Activation Energy (EA) | 0.44 - 0.46 | eV | Energy depth of the VN electron trap centers. |
| Dominant Emission Energy (Peak II, TL) | 3.04 ± 0.01 | eV | Associated with VAl and VAl-ON complexes. |
| Secondary Emission Energy (Peak I, TL) | 2.43 ± 0.06 | eV | Associated with VAl-2ON complexes. |
| TL Heating Rate (r) | 2 | K/s | Rate used for thermal stimulation. |
| Kinetic Order (b) | 2.10 - 2.31 | N/A | Indicates high probability of charge carrier retrapping. |
| Frequency Factor (s) | (1.25 - 2.29) 105 | s-1 | Effective frequency factor. |
Key Methodologies
Section titled “Key Methodologies”- Material Synthesis: Submicron AlN powder was produced using an original gas-phase synthesis method involving the simultaneous processing of liquid aluminum (Al) with gaseous aluminum trifluoride (AlF3) and ammonia (NH3).
- Sample Pre-treatment: Samples were pre-annealed (pre-baked) at 650 K to ensure a baseline state by clearing residual charge traps before experimentation.
- Photoluminescence (PL) Measurement:
- Excitation was performed using UV light at 265 nm.
- Spectra were registered in the 250-700 nm range at a scan speed of 120 nm/min.
- Thermoluminescence (TL) Measurement:
- Trap Filling: Samples were pre-irradiated with UV light at 260 nm for 3 minutes.
- Heating Cycle: Samples were heated from room temperature up to 650 K at a controlled rate of 2 K/s.
- Registration: The TL signal was recorded spectrally resolved (250-650 nm) to generate 3D intensity-wavelength-temperature dependencies.
- Data Analysis: All spectral data (PL and TL) were fitted using a superposition of two independent Gaussian components. Kinetic parameters (EA, frequency factor, kinetic order) were calculated using the General Order Kinetics (GOK) formalism.
Commercial Applications
Section titled “Commercial Applications”The controlled synthesis and characterization of defect-engineered AlN microcrystals are relevant to several high-tech sectors, leveraging AlN’s wide bandgap and thermal properties.
- UV Optoelectronics:
- Application: Deep UV Light-Emitting Diodes (LEDs) and laser diodes.
- Relevance: The dominant 3.0 eV emission peak, linked to VAl-ON complexes, provides insight into defect control necessary for optimizing specific emission wavelengths in UV devices.
- Radiation Dosimetry and Detection:
- Application: Thermoluminescent Dosimeters (TLDs) for measuring ionizing radiation exposure.
- Relevance: The stable VN electron traps (EA ≈ 0.45 eV) and the sharp TL peak at 345 K demonstrate the material’s potential as a sensitive, reusable TLD medium.
- High-Power and High-Frequency Electronics:
- Application: Substrates for High-Electron-Mobility Transistors (HEMTs) and Surface Acoustic Wave (SAW) devices.
- Relevance: AlN’s high thermal conductivity and chemical stability are critical for managing heat dissipation in high-power RF applications.
- Compact Light Sources:
- Application: Fabrication of compact micro-lasers operating in the UV and visible spectrum.
- Relevance: The microcrystalline structure and controlled luminescence characteristics are foundational for developing integrated optical sources.
- Semiconductor Defect Engineering:
- Application: Advanced material synthesis and quality control in III-Nitride semiconductor manufacturing.
- Relevance: The detailed kinetic and spectral analysis of VAl and VN defects provides crucial feedback for optimizing growth recipes to achieve desired electronic properties.
View Original Abstract
The regularities of photo- and thermoluminescence processes in submicrosized AlN crystals with cationic deficiency after UV excitation are studied. The observed emission spectra are a superposition of Gaussian bands with maxima at 3.0 and 2.5 eV. The indicated spectral features are due to electronic transitions involving ON impurity and (VAl -ON) oxygen-vacancy complexes. According to a quantitative analysis in the framework of the general order kinetics, carrier capture centers based on VN nitrogen vacancies have an activation energy of 0.45 eV and are responsible for the forming of the thermally stimulated luminescence with maximum at a temperature of 345 K.