Experimental Insights into Impurity Incorporation in Chemical Vapor Deposition Doped Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-08-27 |
| Journal | physica status solidi (a) |
| Authors | V. Mortet, Axel Leschiutta |
| Institutions | Czech Academy of Sciences, Institute of Physics, Centre National de la Recherche Scientifique |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study provides a comprehensive comparative analysis of boron (B), phosphorus (P), and nitrogen (N) dopant incorporation efficiency (η) in Chemical Vapor Deposition (CVD) diamond, reviewing over 100 literature sources.
- Dopant Hierarchy: Boron exhibits the highest incorporation efficiency, followed by phosphorus, while nitrogen consistently shows the lowest efficiency, despite having the smallest atomic radius.
- Boron Incorporation: B incorporation efficiency is highly scattered and shows no strong correlation with substrate orientation, suggesting extrinsic growth parameters (e.g., methane concentration) are dominant factors. Efficiencies exceeding unity (η > 1) were reported, particularly on unconventional orientations.
- Phosphorus Incorporation: P incorporation is strongly influenced by crystal orientation, with (111) and (113) layers achieving significantly higher concentrations and efficiencies than (100) layers.
- Nitrogen Incorporation: N incorporation efficiency is consistently low and largely insensitive to substrate orientation or standard growth conditions, primarily limited by the poor dissociation of molecular nitrogen (N2).
- Precursor Impact: Using ammonia (NH3) instead of molecular nitrogen (N2) significantly improves N incorporation efficiency, potentially by an order of magnitude.
- Optimization Metric: The findings establish benchmark data for dopant incorporation efficiency (η) as a function of the dopant-to-carbon precursor ratio (D/C)g, providing a critical reference for optimizing doped diamond synthesis.
- Promising Orientations: Unconventional orientations like (113) are highlighted as promising platforms due to their combination of high growth rates, enhanced dopant incorporation, and excellent surface quality.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Carbon Atomic Concentration (Cdiamond) | 1.764 x 1023 | cm-3 | Used for calculating (D/C)s ratio |
| Boron Ionization Energy (IE) | 0.36 | eV | Substitutional acceptor |
| Phosphorus Ionization Energy (IE) | 0.6 | eV | Deep donor |
| Nitrogen Ionization Energy (IE) | 1.4 | eV | Very deep donor |
| Highest Reported B Concentration | 8.5 x 1021 | cm-3 | Achieved in (111) epitaxial layer |
| Highest Reported P Concentration | 6 x 1020 | cm-3 | Achieved in epitaxial layer |
| Highest Reported N Concentration (Epitaxial) | 3.3 x 1020 | cm-3 | Achieved using N2 precursor |
| B Incorporation Efficiency (η) | > 1 | Unitless | Observed on unconventional orientations (e.g., (113)) |
| P Incorporation Efficiency (η) | â 2.3 | Unitless | Highest reported value |
| N Incorporation Efficiency (vs. P) | 40-400 times lower | Unitless | Comparison at a given (D/C)g ratio |
| Boron Atomic Radius | 0.085 | nm | Comparison metric |
| Phosphorus Atomic Radius | 0.100 | nm | Comparison metric |
| Nitrogen Atomic Radius | 0.065 | nm | Comparison metric |
| N2 Bond Dissociation Energy | â 9.8 | eV | High stability, limits dissociation in PECVD |
| NH3 Bond Dissociation Energy | â 4.9 | eV | Lower stability, enhances N radical generation |
Key Methodologies
Section titled âKey MethodologiesâThe study is a comprehensive review and analysis of experimental data from over 100 publications focusing on diamond doping.
- Growth Technique: Data primarily derived from Plasma-Enhanced Chemical Vapor Deposition (PECVD) and, to a lesser extent, Hot Filament CVD (HFCVD) growth of single-crystal epitaxial diamond layers.
- Dopant Precursors:
- Boron: Diborane (B2H6) and Trimethylborane (TMB, B(CH3)3).
- Phosphorus: Phosphine (PH3), Trimethylphosphine (TMP), and Tripropyl borate (TBP).
- Nitrogen: Molecular nitrogen (N2), Ammonia (NH3), and Nitrous Oxide (N2O).
- Primary Variables Investigated: The influence of two critical synthesis parameters was analyzed:
- Dopant-to-Carbon ratio in the gas phase ((D/C)g).
- Substrate crystalline orientation ((100), (111), (110), (113), (115), (118)).
- Data Acquisition and Processing:
- Numerical data were extracted directly from text or digitized from graphs using GetData Graph Digitizer software (estimated uncertainty ± 10%).
- The atomic dopant-to-carbon ratio in the solid ((D/C)s) was calculated using the diamond carbon concentration (1.764 x 1023 cm-3).
- Key Characterization Method: Dopant concentrations in the solid phase (Ds) were predominantly measured using Secondary Ion Mass Spectrometry (SIMS). Other methods like Electron Paramagnetic Resonance and Raman spectroscopy were also included.
- Efficiency Calculation: Incorporation efficiency (η) was defined and calculated as the ratio of the atomic concentration in the solid to the atomic concentration in the gas phase: η = (D/C)s / (D/C)g.
Commercial Applications
Section titled âCommercial ApplicationsâThe controlled incorporation of dopants in CVD diamond is essential for high-performance devices across several sectors:
| Application Sector | Dopant/Feature Required | Technical Benefit |
|---|---|---|
| High-Power Electronics | Boron (p-type), Phosphorus (n-type) | Fabrication of diodes, MOSFETs, and transistors; enabling high-voltage, high-frequency operation due to wide bandgap. |
| Quantum Technologies | Nitrogen (for NV centers) | Creation of stable, optically active nitrogen-vacancy (NV) centers for quantum sensing, computing, and magnetometry. |
| Electrochemistry | High-concentration Boron (p+) or Phosphorus (n+) | Creation of low-specific-resistance ohmic contacts and robust, chemically inert electrodes for harsh environments. |
| Advanced Substrates | (113), (115), (118) Orientations | Optimized growth platforms offering enhanced dopant uptake and higher growth rates compared to conventional (100) and (111) substrates. |
| Electron Emitters | Phosphorus-doped diamond | Utilization in cold cathode applications due to negative electron affinity properties. |
View Original Abstract
Diamondâs exceptional properties as a wide bandgap semiconductor make it a leading candidate for nextâgeneration power electronics and quantum technologies. However, achieving precise control over the incorporation of active dopants, such as boron, phosphorus, and nitrogen, remains a key challenge in the fabrication of diamondâbased devices. Herein, over 100 literature sources are reviewed and analyzed to evaluate and compare dopant incorporation efficiency in singleâcrystal diamond synthesized via chemical vapor deposition. It also incorporates some data from polycrystalline layers for broader comparison. Specifically, the influence of dopant precursor concentration in the plasma and substrate orientation is investigated. The findings offer new insights and provide a useful reference metric for optimizing doped diamond synthesis.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2020 - Semiconductors And Semimetals