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6CCVD Research

Diamond for High-Power, High-Frequency, and Terahertz Plasma Wave Electronics

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2024-03-01
JournalNanomaterials
AuthorsMuhammad Mahmudul Hasan, Chunlei Wang, Nezih Pala, M. S. Shur
InstitutionsFlorida International University, Rensselaer Polytechnic Institute
Citations21
AnalysisFull AI Review Included

Diamond for High-Power, High-Frequency, and Terahertz Plasma Wave Electronics

Section titled “Diamond for High-Power, High-Frequency, and Terahertz Plasma Wave Electronics”

Technical Documentation and Sales Analysis based on Nanomaterials 2024, 14, 460

Executive Summary

Section titled “Executive Summary”
  • Superior Material Performance: Diamond exhibits exceptional Figures of Merit (CFOM, BFOM, JFOM) surpassing SiC, GaN, and Ga2O3, primarily due to its ultra-wide bandgap (5.47 eV), high breakdown field (10 MV/cm), and industry-leading thermal conductivity (2200 W/mK).
  • High-Power Device Achievement: Diamond Schottky Barrier Diodes (SBDs) have demonstrated breakdown voltages exceeding 10 kV, confirming diamond’s potential for extreme high-power switching applications.
  • RF and Microwave Leadership: Diamond Field Effect Transistors (FETs), particularly H-terminated MOSFETs, have achieved competitive RF performance, including output power densities up to 3.8 W/mm (at 1 GHz) and maximum oscillation frequencies (fmax) up to 120 GHz.
  • THz and 6G Potential: Diamond’s exceptionally long carrier momentum relaxation time facilitates resonant plasma wave operation in TeraFETs, making p-diamond a promising candidate for compact, room-temperature THz sources and detectors.
  • Targeted Frequency Range: Analytical studies predict diamond TeraFET viability for the 240-600 GHz atmospheric window, crucial for next-generation 6G communication systems.
  • Growth Technology Focus: Microwave Plasma-Assisted CVD (MPCVD) is the established method for producing the high-quality Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) films necessary for these advanced electronic devices.
  • Material Challenges: Key areas for continued research include scaling up low-defect SCD substrate size and improving the efficiency and mobility of n-type doping (Phosphorus).

Technical Specifications

Section titled “Technical Specifications”

The following hard data points highlight diamond’s superlative properties relative to competing Wide Bandgap (WBG) materials, as extracted from the review (Table 1, Figures 1, 4, 12).

ParameterValueUnitContext
Energy Bandgap (EG)5.47eVUltra-wide bandgap semiconductor (UWBGS)
Breakdown Field (EB)10MV/cmHighest reported value
Thermal Conductivity (χ)2200W/mKRoom Temperature (RT)
Intrinsic Electron Mobility (”e)7300cm2/VsUltrapure Single Crystal Diamond (SCD)
Intrinsic Hole Mobility (”h)5300cm2/VsUltrapure Single Crystal Diamond (SCD)
Electron Saturation Velocity (vs)2.7 x 107cm/sHigh-frequency operation limit
Combined Figure of Merit (CFOM)124,424Relative to SiHighest overall performance metric
Highest SBD Breakdown Voltage>10kVHigh-power rectifier application
Highest FET Output Power Density3.8W/mmH-terminated MOSFET (1 GHz)
Maximum Frequency (fmax)120GHzPolycrystalline H-FET (100 nm gate length)
TeraFET Resonant Frequency200-400GHzPredicted for p-diamond (80-120 nm channel)
SCD Dislocation Density (Homoepitaxy)102-105cm-2High-quality CVD growth target

Key Methodologies

Section titled “Key Methodologies”

The research reviewed focuses on advanced material growth and doping techniques essential for realizing high-performance diamond devices.

  1. CVD Growth Technology: Microwave Plasma-Assisted CVD (MPCVD) is the preferred method for producing high-quality SCD and PCD films for electronics. This process utilizes reactant gases (H2, CH4) and high microwave power density (up to 3.8 kW cm-3 reported) to achieve high growth rates (up to 60 ”m h-1).
  2. Homoepitaxy vs. Heteroepitaxy:
    • Homoepitaxy: Growth on diamond seed crystals, yielding the highest quality SCD (dislocation density 102-105 cm-2), but limited by initial seed size (<1 cm2, though mosaic arrays up to 40 x 60 mm2 are being explored).
    • Heteroepitaxy: Growth on non-diamond substrates (e.g., Ir/Si, Ir/YSZ/Si, Sapphire) to achieve larger wafer sizes (up to 3.5 inches reported), but typically resulting in higher defect densities (108-109 cm-2).
  3. P-Type Doping (Boron): Boron is incorporated in situ during CVD growth, often using Diborane or Trimethylboron. Boron-Doped Diamond (BDD) is well-established for creating p-type layers, p-i-n junctions, and highly conductive p+ ohmic contacts.
  4. N-Type Doping (Phosphorus): Phosphorus doping, typically using PH3, is the most successful n-type method, achieving Hall mobilities up to 1060 cm2/Vs. High P concentrations (1020 cm-3) are used to form n+ ohmic contacts, crucial for Bipolar Junction Transistors (BJTs).
  5. Surface Transfer Doping (2DHG): This technique creates a high-mobility 2D Hole Gas (2DHG) channel on hydrogen-terminated diamond surfaces (H-FETs). Passivation layers, such as Atomic Layer Deposition (ALD) Al2O3, MoO3, or V2O5, are used as electron acceptors to stabilize the channel and improve reliability.
  6. High-Frequency Device Structures: TeraFETs capitalize on plasma wave oscillations in the 2DEG/2DHG channel, requiring extremely short gate lengths (down to 100 nm) and high carrier mobility to achieve resonant detection in the THz regime.

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

6CCVD is uniquely positioned to supply the high-quality MPCVD diamond materials and custom engineering services required to replicate and advance the high-power and THz electronics research detailed in this review.

Applicable Materials

Section titled “Applicable Materials”

To meet the stringent requirements for high-power and high-frequency diamond devices, 6CCVD recommends the following materials from our catalog:

  • Optical Grade Single Crystal Diamond (SCD): Essential for achieving the highest intrinsic carrier mobilities (up to 7300 cm2/Vs) and lowest dislocation densities (102-105 cm-2). This material is critical for high-performance TeraFETs and high-voltage vertical SBDs where crystal quality dictates breakdown field.
  • High-Purity Polycrystalline Diamond (PCD): Ideal for large-area, high-power modules and heat spreading applications where thermal conductivity (2200 W/mK) is paramount. Our PCD offers a scalable solution for devices requiring wafers larger than 1 cm2.
  • Boron-Doped Diamond (BDD) Films: Necessary for creating the p-type layers, p-i-n junctions, and low-resistance ohmic contacts (p+) required for SBDs and p-channel MOSFETs/TeraFETs. We offer precise control over B concentration for optimal conductivity tuning.

Customization Potential

Section titled “Customization Potential”

The development of state-of-the-art diamond devices often requires non-standard dimensions, specific layer thicknesses, and complex metalization schemes. 6CCVD provides comprehensive customization capabilities:

Custom Requirement6CCVD CapabilityRelevance to High-Power/THz Devices
Large Wafer SizePCD plates/wafers up to 125 mm diameter.Enables industrial scaling of high-power modules and large-area TeraFET arrays, overcoming the size limitations of HPHT seeds.
Epitaxial Thickness ControlSCD and PCD films from 0.1 ”m up to 500 ”m.Allows precise engineering of active device layers (e.g., thin delta-doped layers or thick drift layers for high-voltage SBDs).
Thick SubstratesSubstrates available up to 10 mm thick.Provides robust thermal management for devices achieving high output power densities (up to 3.8 W/mm).
Advanced MetalizationInternal capability for Au, Pt, Pd, Ti, W, Cu deposition.Essential for optimizing Schottky barrier height (SBH) and creating stable, low-resistance ohmic contacts (e.g., Ti/Pt/Au stacks) required for high-temperature operation.
Surface FinishPolishing to achieve Ra < 1 nm (SCD) and Ra < 5 nm (PCD).Critical for H-FETs and 2DHG devices, where ultra-smooth surfaces minimize interface trap density and maximize channel mobility.

Engineering Support

Section titled “Engineering Support”

6CCVD’s in-house PhD team specializes in MPCVD diamond synthesis and device physics. We offer authoritative professional support to researchers and engineers tackling complex challenges:

  • Material Selection for TeraFETs: We assist in selecting the optimal SCD or high-quality PCD substrate orientation ((110) or (100)) and surface termination (H-terminated) to maximize hole momentum relaxation time (τ) and achieve resonant operation in the 240-600 GHz range.
  • High-Voltage Device Design: Consultation on optimizing SCD layer thickness and BDD concentration to achieve desired breakdown voltages (>10 kV) and minimize specific ON resistance for high-power SBD and BJT projects.
  • N-Type Doping Strategies: Support for projects involving n-type diamond, including material specifications for Phosphorus-doped layers and the integration of custom metalization for low-resistance n+ ohmic contacts.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

High thermal conductivity and a high breakdown field make diamond a promising candidate for high-power and high-temperature semiconductor devices. Diamond also has a higher radiation hardness than silicon. Recent studies show that diamond has exceptionally large electron and hole momentum relaxation times, facilitating compact THz and sub-THz plasmonic sources and detectors working at room temperature and elevated temperatures. The plasmonic resonance quality factor in diamond TeraFETs could be larger than unity for the 240-600 GHz atmospheric window, which could make them viable for 6G communications applications. This paper reviews the potential and challenges of diamond technology, showing that diamond might augment silicon for high-power and high-frequency compact devices with special advantages for extreme environments and high-frequency applications.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2005 - THz imaging and sensing for security applications—Explosives, weapons and drugs [Crossref]
  2. 2019 - Sub-terahertz testing of millimeter wave monolithic and very large scale integrated circuits [Crossref]
  3. 2017 - Terahertz beam testing of millimeter wave monolithic integrated circuits [Crossref]

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