CVD diamond with boron-doped delta-layers deposited by microwave plasma
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2017-01-01 |
| Journal | EPJ Web of Conferences |
| Authors | A. L. Vikharev, Š. Š. ŠŠ¾ŃŠ±Š°ŃŠµŠ², M. A. Lobaev, D.B. Radishev, V. A. Isaev |
| Institutions | Institute for Physics of Microstructures, Institute of Applied Physics |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Boron Delta-Doped CVD Diamond
Section titled āTechnical Documentation & Analysis: Boron Delta-Doped CVD DiamondāReference: Vikharev et al., EPJ Web of Conferences 149, 01010 (2017). Topic: CVD diamond with boron-doped delta-layers deposited by microwave plasma for high-frequency electronics.
Executive Summary
Section titled āExecutive SummaryāThis research successfully demonstrates the fabrication of high-quality, heavily boron-doped (BDD) delta-layers in single-crystal diamond (SCD) using specialized Microwave Plasma CVD (MPCVD). The findings are critical for developing next-generation high-power and high-frequency electronic devices.
- High Performance: Achieved a maximum hole mobility of 300 cmĀ²/VĀ·s at room temperature, significantly enhanced by the spatial separation of holes and boron dopant atoms (delta-doping effect).
- Low Activation Energy: The activation energy of boron in the delta layer was dramatically reduced to ~60 meV, compared to the bulk diamond value of 370 meV.
- Ultra-Sharp Interfaces: The use of a novel MPCVD reactor with rapid gas switching enabled the creation of ultra-sharp interfaces, essential for the delta-doping mechanism.
- Extreme Doping: Boron concentrations reached up to 4.8 x 1020 cm-3 within nanometric layers (1-2 nm thickness).
- Advanced Fabrication: The study involved complex device fabrication, including lithographic etching of mesa structures (25-400 Āµm) and multi-layer metalization schemes (Ti/Mo/Au and Cr/Al).
- 6CCVD Value Proposition: 6CCVD specializes in providing the Electronic Grade SCD substrates and precise BDD layer control necessary to replicate and scale this high-mobility technology.
Technical Specifications
Section titled āTechnical SpecificationsāThe following hard data points were extracted from the research paper detailing the material properties and device characteristics.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Boron Concentration (Max) | 4.8 x 1020 | cm-3 | Heavily doped delta layer (Sample SS6-1) |
| Delta Layer Thickness | 1 - 2 | nm | Required for quantum confinement effects |
| Maximum Hole Mobility | 300 | cmĀ²/VĀ·s | Measured via Van der Pau method at room temperature |
| Activation Energy (Delta Layer) | ~60 | meV | Measured via C-V analysis (significantly reduced) |
| Activation Energy (Bulk Diamond) | 370 | meV | Standard reference for bulk boron-doped diamond |
| Diamond Growth Rate | 40 - 100 | nm/h | Slow growth regime used to ensure interface sharpness |
| Reactor Gas Residence Time | ~5 | s | Required for rapid gas switching |
| Mesa Structure Diameter | 25 to 400 | Āµm | Formed by lithographic masking and etching |
| Ohmic Contact Metalization | Ti/Mo/Au | N/A | Deposited on heavily doped p++ layer |
| Schottky Contact Metalization | Cr/Al | N/A | Deposited on top of the mesas |
Key Methodologies
Section titled āKey MethodologiesāThe successful fabrication of high-mobility delta-doped layers relied on precise control of the MPCVD environment and subsequent device processing.
- Novel MPCVD Reactor: Utilization of a specialized reactor featuring an axial symmetric resonant mode, laminar gas flow, and an electronic switch for rapid gas switching.
- Substrate Selection: Use of high-quality, defect-free Single Crystal Diamond (SCD) substrates for homoepitaxial growth.
- Controlled Growth Rate: Employing a slow growth rate (40-100 nm/h) combined with rapid gas switching (residence time ~5 s) to achieve nanometric layer thickness and ultra-sharp doped/undoped boundaries.
- Heavy Boron Doping: Introduction of boron during the 1-2 nm growth phase to achieve concentrations exceeding 5 x 1020 cm-3.
- Mesa Structure Definition: Formation of device structures (25-400 Āµm diameter) using lithographic masking and etching down to the underlying heavily doped layer.
- Ohmic Contact Formation: Deposition of the Ti/Mo/Au metal stack onto the heavily doped p++ layer, followed by annealing to ensure low-resistance ohmic behavior.
- Schottky Contact Formation: Deposition of the Cr/Al metal stack onto the top surface of the mesas.
- Material Characterization: Verification of boron concentration and depth profile using Secondary Ion Mass Spectroscopy (SIMS) and measurement of electrical properties (hole concentration, mobility) using Capacitance-Voltage (C-V) and Van der Pau methods.
6CCVD Solutions & Capabilities
Section titled ā6CCVD Solutions & Capabilitiesā6CCVD is uniquely positioned to supply the high-specification diamond materials and advanced processing required to replicate, optimize, and scale this high-mobility delta-doping technology for commercial applications in high-frequency electronics.
Applicable Materials
Section titled āApplicable MaterialsāTo achieve the performance metrics described (high mobility, sharp interfaces), the highest quality diamond is essential.
| Research Requirement | 6CCVD Material Solution | Key Specification Match |
|---|---|---|
| High-Quality Substrate | Electronic Grade Single Crystal Diamond (SCD) | Defect-free material required for homoepitaxy and high carrier mobility in undoped layers. Polishing available to Ra < 1nm. |
| Active Doped Layer | Heavy Boron-Doped Diamond (BDD) | 6CCVD offers precise control over BDD concentration, essential for achieving the required 1020 cm-3 doping level in nanometric layers. |
| Large Area Devices | Polycrystalline Diamond (PCD) | While SCD was used here, 6CCVD can provide large-area PCD wafers up to 125mm for scaling applications where the active layer is thin and surface quality is paramount (Ra < 5nm for inch-size PCD). |
Customization Potential
Section titled āCustomization PotentialāThe complexity of the device structure requires advanced post-processing capabilities, which 6CCVD provides in-house.
- Custom Metalization Schemes: The paper utilized complex Ti/Mo/Au (Ohmic) and Cr/Al (Schottky) stacks. 6CCVD offers internal metalization capabilities including Au, Pt, Pd, Ti, W, and Cu. We can engineer and deposit multi-layer stacks, including refractory metals, to meet specific contact resistance and thermal stability requirements.
- Precision Thickness Control: The delta layers are 1-2 nm thick. 6CCVD guarantees thickness control for both SCD and PCD layers from 0.1 Āµm up to 500 Āµm, allowing for precise control of the undoped buffer and cap layers surrounding the active delta-doped region.
- Custom Dimensions and Substrates: 6CCVD supplies custom SCD substrates up to 10mm thick and can provide laser cutting services to achieve specific geometries required for device prototyping and integration.
Engineering Support
Section titled āEngineering SupportāThe successful implementation of delta-doping relies on optimizing the CVD recipe (gas flow, pressure, temperature) to achieve the required sharp transition profiles.
- CVD Recipe Optimization: 6CCVDās in-house PhD team specializes in optimizing MPCVD growth parameters for advanced applications, including precise control of dopant incorporation and interface quality, critical for high-frequency/high-power electronics projects.
- Material Selection Consultation: We provide expert guidance on selecting the optimal diamond grade (SCD vs. PCD) and doping level (BDD) to maximize carrier mobility and minimize activation energy for similar high-frequency device applications.
- Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive, high-value diamond materials directly to your research facility.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.