Interaction of Dopants with the I3-Type Basal Stacking Fault in Hexagonal-Diamond Si
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-06-05 |
| Journal | The Journal of Physical Chemistry C |
| Authors | Marc TĂșnica, Perpetua Wanjiru Muchiri, Alberto Zobelli, Anna Marzegalli, Emilio Scalise |
| Institutions | Centre National de la Recherche Scientifique, Université Paris-Saclay |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Analysis: Dopant Segregation in Hexagonal-Diamond Structures
Section titled âTechnical Analysis: Dopant Segregation in Hexagonal-Diamond StructuresâThis document analyzes the findings of the research paper âInteraction of dopants with the I3-type basal stacking fault in hexagonal-diamond Siâ using the perspective of 6CCVD, an expert supplier of MPCVD diamond materials for advanced engineering applications. The study provides critical insights into defect-dopant interactions, a core challenge in developing high-performance Group IV semiconductors, including diamond polytypes.
Executive Summary
Section titled âExecutive Summaryâ- Core Research Focus: First-principles Density Functional Theory (DFT) simulations investigating the thermodynamic stability and segregation behavior of extrinsic dopants (B, Al, Ga, In, N, P, As, Sb, C, Ge) near I3-type basal stacking faults (I3-BSF) in hexagonal-diamond silicon (hex-Si).
- Acceptor Repulsion: Neutral and negatively charged p-type acceptors (Al, Ga, In) exhibit a strong positive dopant segregation energy (DSE, up to 140 meV), indicating a thermodynamic driving force to repel these dopants away from the I3-BSF defect planes.
- Donor Neutrality: Neutral and charged n-type donors (P, As, Sb) show negligible or small DSE variations (typically < 40 meV), suggesting the I3-BSF does not act as a significant repulsive barrier for these impurities.
- Key Mechanism: The segregation trend is primarily attributed to the interplay between the dopantâs steric effects (covalent radius mismatch with Si) and the change in local symmetry (from C3v in bulk hex-Si to Td in the cubic-like fault region).
- Critical Exceptions: Boron (B) and Carbon (C) show unique behavior. C exhibits negative DSE (segregation into the fault), while ionized Bâ» also shows negative DSE, suggesting the I3-BSF acts as an energy sink for these small-radius impurities.
- Implications for Device Design: These findings are crucial for defect-dopant engineering, suggesting that controlling stacking faults can be used to create functional, anisotropic doping profiles in hex/cub-Si heterostructures, relevant for next-generation optoelectronic and high-power devices.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Crystal Structure Analyzed | Hexagonal-Diamond Si (hex-Si) | N/A | Focus on I3-type basal stacking fault (I3-BSF) |
| Optimized Lattice Parameter (aSi) | 3.84 | Ă | Hex-Si crystal cell, GGA-PBE functional |
| Optimized Lattice Parameter (cSi) | 6.34 | Ă | Hex-Si crystal cell, GGA-PBE functional |
| Stacking Fault Energy (ÎłI3-BSF) | â -85 | mJ/mÂČ | Negative value indicates energetic stability of the defect |
| Simulated Doping Concentration | 1.3 x 1020 | cm-3 | High doping regime used in 4x4x6 supercell (384 atoms) |
| Max DSE (Neutral Acceptors) | 80 - 140 | meV | Al, Ga, In in Region II (repulsion from BSF) |
| Max DSE (Neutral Donors) | 20 - 70 | meV | P, As, Sb (low repulsion); N (high repulsion) |
| DSE (Ionized Bâ» Acceptor) | -40 | meV | Negative DSE close to fault (attraction/segregation) |
| DSE Reduction (Ionization) | 43 - 80 | % | Reduction observed for Alâ», Gaâ», Inâ» compared to neutral state |
| Structural Convergence Criteria | < 10-2 | eV/Ă | Maximum force tolerance during DFT optimization |
| Stress Convergence Criteria | < 10-1 | GPa | Maximum stress tolerance during DFT optimization |
Key Methodologies
Section titled âKey MethodologiesâThe study employed advanced computational materials science techniques to model defect behavior:
- Simulation Framework: Spin-polarized ab initio Density Functional Theory (DFT) simulations were performed using the SIESTA code.
- Functional and Pseudopotentials: The Generalized Gradient Approximation (GGA) with the Perdew, Burke, and Ernzerhof (PBE) functional was utilized, along with Troullier-Martins norm-conserving pseudopotentials.
- Basis Sets: A double-ζ polarized basis set was used for Si valence electrons, and a double-ζ basis set plus two polarization orbitals was used for dopant atoms.
- Supercell Construction: Bulk supercells (4x4x6, 384 atoms) were constructed to simulate hex-Si containing an infinitely extended I3-BSF, minimizing spurious electrostatic interactions between periodic images.
- Dopant Analysis: Common substitutional dopants (B, Al, Ga, In, N, P, As, Sb, C, Ge) were introduced at a concentration of 1.3 x 1020 cm-3.
- Energy Calculation: Dopant Segregation Energy (DSE) was calculated as the difference between the total ground-state energy of the defective system with the dopant at position z and the reference energy (dopant farthest from the fault).
- Charged Impurities: Calculations for charged impurities (e.g., Bâ», Pâș) included a compensating jellium background to maintain charge neutrality and avoid electrostatic divergence.
- Interface Validation: Results were validated by comparing I3-BSF behavior to an abrupt hex/cub-Si interface (448 atoms), representing the extreme case of the local cubic configuration.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe findings regarding dopant segregation and defect interaction in Group IV hexagonal structures have direct relevance to the engineering and optimization of MPCVD diamond (SCD/PCD) materials, particularly for applications requiring precise control over electrical activation and defect density (e.g., quantum sensing, high-power electronics).
Applicable Materials
Section titled âApplicable MaterialsâThe research highlights the critical role of Boron (B) and Nitrogen (N) in defect interaction, which are the two most common dopants in CVD diamond. 6CCVD offers materials specifically engineered to leverage or mitigate these effects:
| Research Requirement | 6CCVD Material Solution | Technical Advantage for Replication/Extension |
|---|---|---|
| Boron Doping (B/Bâ») | Boron-Doped Diamond (BDD) Plates | BDD is essential for p-type conductivity. The paperâs finding that Bâ» segregates into defects suggests BDD material requires careful defect control (e.g., stacking faults, dislocations) to ensure uniform electrical activation. 6CCVD offers BDD with custom resistivity ranges. |
| Nitrogen Doping (N) | High Purity Single Crystal Diamond (SCD) | N is the precursor for NV centers (quantum defects). The paper shows N has a high DSE peak (70 meV), indicating strong repulsion from cubic-like defects. 6CCVD provides high-purity SCD where N concentration is tightly controlled for NV center creation or minimization. |
| High Doping Concentration | Heavy Boron Doped PCD/SCD | The study used a high doping concentration (1.3 x 1020 cm-3). 6CCVD can achieve heavy doping in both SCD and PCD, enabling research into high-concentration effects and dopant clustering relevant to the steric analysis presented. |
| Defect/Interface Study | Polycrystalline Diamond (PCD) Wafers | PCD inherently contains grain boundaries and stacking faults, which mimic the extended defects studied. 6CCVD offers large-area PCD (up to 125mm) with controlled grain size, ideal for studying bulk defect-dopant interactions in a diamond matrix. |
Customization Potential
Section titled âCustomization PotentialâThe ability to precisely control material dimensions, purity, and surface characteristics is paramount for translating theoretical defect physics into functional devices.
- Custom Dimensions: While the paper focuses on nanowires, 6CCVD provides bulk plates and wafers up to 125mm (PCD) and 500”m (SCD) thick. This allows researchers to scale up defect-engineered structures.
- Precision Polishing: The structural analysis relies on atomic-level symmetry. 6CCVD offers ultra-smooth polishing (Ra < 1nm for SCD, < 5nm for inch-size PCD), ensuring that surface defects do not overshadow bulk defect studies.
- Metalization Services: For creating functional hex/cub-Si heterostructures or diamond-based devices, custom contacts are necessary. 6CCVD offers in-house metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu, allowing for direct integration of defect-engineered materials into device architectures.
Engineering Support
Section titled âEngineering SupportâThe complex interplay between steric effects, charge state, and wave function symmetry requires deep material expertise. 6CCVDâs in-house PhD team specializes in defect engineering and CVD growth kinetics.
- Material Selection for Defect Engineering: Our experts can assist researchers in selecting the optimal diamond polytype (SCD vs. PCD) and doping level to replicate or extend the findings of this study, particularly for projects involving quantum defect creation (NV centers) or high-power semiconductor design, where controlling dopant segregation near extended defects is critical for performance.
- Global Logistics: 6CCVD supports global research efforts with reliable shipping (DDU default, DDP available), ensuring materials reach international labs efficiently.
Call to Action: For custom specifications or material consultation regarding defect-engineered SCD, BDD, or PCD, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Recently synthesized hexagonal-diamond silicon, germanium, and silicon-germanium nanowires exhibit remarkable optical and electronic properties when compared to cubic-diamond polytypes. Because of the metastability of the hexagonal-diamond phase, I3-type basal stacking faults are frequently observed in these materials. Understanding and modulating the interaction between these extended defects and dopants are essential for advancing the design and performance of these novel semiconductors. In the present study, we employ density functional theory calculations to investigate the interaction of extrinsic dopants (group III, IV, and V elements) with the I3-type basal stacking fault in hexagonal-diamond silicon. Contrary to the behavior observed in cubic-diamond silicon with intrinsic stacking faults, we demonstrate that neutral and negatively charged p-type impurities exhibit a marked tendency to occupy lattice sites far from the I3-type basal stacking fault. The interaction of acceptors with the planar defect reduces their energetic stability. However, this effect is much less pronounced for neutral or positively charged n-type dopants and isovalent impurities. The thermodynamic energy barrier to segregation for these dopants is small and may even become negative, indicating a tendency to segregate into the fault. Through a detailed analysis of structural modifications, ionization effects, and impurity-level charge density distribution, we show that the origin of this behavior can be attributed to variations in the impurityâs steric effects and its wave function character. Finally, all these results are validated by considering the extreme case of an abrupt hexagonal/cubic silicon interface, where acceptor segregation from the cubic to the hexagonal region is demonstrated, confirming the behavior observed for p-type dopants near the I3-type defect.