p-Diamond, Si, GaN, and InGaAs TeraFETs
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-10-12 |
| Journal | IEEE Transactions on Electron Devices |
| Authors | Yuhui Zhang, M. S. Shur |
| Institutions | Rensselaer Polytechnic Institute |
| Citations | 22 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: p-Diamond TeraFETs for Sub-THz Applications
Section titled âTechnical Documentation & Analysis: p-Diamond TeraFETs for Sub-THz ApplicationsâExecutive Summary
Section titled âExecutive SummaryâThis research confirms that p-type diamond is the optimal material system for high-sensitivity, resonant Terahertz (THz) Field Effect Transistors (TeraFETs), offering significant advantages over Si, GaN, and InGaAs.
- Superior Material Performance: p-Diamond TeraFETs exhibit the highest DC response and detection sensitivity across a large frequency window (up to 6 THz) due to their high effective mass and long momentum relaxation time ($\tau$).
- Resonant Operation in Sub-THz: The material enables resonant plasmonic operation in the critical 200 GHz to 600 GHz band, essential for beyond 5G sub-THz communications.
- Low Critical Mobility: p-Diamond requires the lowest minimum resonant mobility ($\mu_{\tau} \approx 700 \text{ cm}^{2}\cdot\text{V}^{-1}\text{s}^{-1}$), simplifying the realization of resonant detection compared to other semiconductors.
- Favorable Scaling: As feature sizes scale down (e.g., channel length reduced to 20 nm), the relative performance of p-diamond improves, yielding the highest DC response among all tested materials.
- Cryogenic Enhancement: Detection sensitivity is substantially enhanced at cryogenic temperatures (77 K) due to the significant increase in carrier mobility (up to $35000 \text{ cm}^{2}\cdot\text{V}^{-1}\text{s}^{-1}$).
- 6CCVD Value Proposition: 6CCVD specializes in the high-quality, Boron-Doped Diamond (BDD) required to achieve the high carrier mobility and low ohmic contact resistance critical for replicating and advancing this TeraFET technology.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the simulation and material analysis, highlighting the intrinsic advantages of p-diamond for TeraFET applications.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Effective Mass (Hole) | 0.74 | $m/m_{0}$ | p-Diamond (High effective mass contributes to long $\tau$) |
| Carrier Mobility (300 K) | 5300 | $\text{cm}^{2}\cdot\text{V}^{-1}\text{s}^{-1}$ | p-Diamond (Room Temperature) |
| Carrier Mobility (77 K) | 35000 | $\text{cm}^{2}\cdot\text{V}^{-1}\text{s}^{-1}$ | p-Diamond (Cryogenic Temperature) |
| Minimum Resonant Mobility ($\mu_{\tau}$) | $\approx 700$ | $\text{cm}^{2}\cdot\text{V}^{-1}\text{s}^{-1}$ | p-Diamond (Lowest required for resonant operation) |
| Resonant Frequency Window | 200 to 600 | GHz | Target range for beyond 5G sub-THz communications |
| Channel Lengths Simulated | 20, 65, 130 | nm | Feature sizes demonstrating scaling advantage |
| Bandgap Energy | $\approx 5.46$ | eV | Diamond (Wide bandgap) |
| Thermal Conductivity | $\approx 23$ | $\text{W}/\text{cm}\cdot\text{K}$ | Diamond (High thermal management capability) |
Key Methodologies
Section titled âKey MethodologiesâThe TeraFET performance analysis was conducted using a rigorous hydrodynamic modeling approach, focusing on key material and device parameters.
- Modeling Framework: A one-dimensional hydrodynamic model was employed to trace the generation and propagation of plasma waves in gated TeraFETs.
- Material Systems: Simulations compared p-diamond against n-diamond, Si, GaN, and InGaAs, utilizing reported maximum carrier mobilities for each material.
- Device Scaling: The effect of feature size was analyzed by simulating gate lengths ($L$) of 20 nm, 65 nm, and 130 nm.
- Temperature Variation: Performance was evaluated at both room temperature (300 K) and cryogenic temperature (77 K) to assess mobility and sensitivity enhancement.
- Response Time Analysis: The ultimate response time ($\tau_{r}$) was calculated using an ultra-short square-pulse signal ($5 \times 10^{-14} \text{ s}$) to determine the transition mobility ($\mu_{\tau}$) required for resonant operation.
- DC Response Calculation: Normalized DC voltage response ($R$) was simulated as a function of gate bias ($U_{0}$) and frequency ($f$) to identify peak resonant performance.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research highlights the necessity of high-quality, high-mobility p-type diamond substrates for next-generation TeraFETs. 6CCVD is uniquely positioned to supply the required materials and custom processing necessary to replicate and advance this research.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the high carrier mobility (up to $35000 \text{ cm}^{2}\cdot\text{V}^{-1}\text{s}^{-1}$ at 77 K) and low ohmic contact resistance required for resonant TeraFET operation, 6CCVD recommends:
- Single Crystal Diamond (SCD): High-purity, electronic-grade SCD is essential for maximizing carrier mobility and minimizing defects, particularly for small-feature-size devices (20 nm scale).
- Boron-Doped Diamond (BDD-SCD/PCD): Controlled, uniform boron doping is required to create the p-type channel. 6CCVD offers precise doping concentrations necessary to optimize the plasma frequency ($\omega_{p}$) and meet the plasmonic resonance condition ($\omega_{p}\tau > 1$).
- Polycrystalline Diamond (PCD) Substrates: For large-area THz imaging or sensing arrays, 6CCVD can supply high-quality PCD plates up to 125 mm in diameter, offering a cost-effective solution for scaling production.
Customization Potential
Section titled âCustomization PotentialâThe fabrication of TeraFETs, especially those targeting 20 nm channel lengths, requires highly specialized substrates and processing capabilities that 6CCVD provides:
| Requirement from Research | 6CCVD Capability | Technical Advantage |
|---|---|---|
| Ultra-Smooth Surface | Polishing to $R_{a} < 1 \text{ nm}$ (SCD) | Essential for minimizing scattering and maximizing carrier mobility in the 2D channel. |
| Small Feature Fabrication | Custom laser cutting and shaping | Provides precise dimensions for subsequent nanofabrication processes (E-beam lithography, etc.) used to define 20 nm features. |
| Ohmic Contacts | Custom Metalization Services | Internal capability to deposit critical metal stacks (e.g., Ti/Pt/Au, W, Cu) required for achieving the low ohmic contact resistance cited as advantageous for diamond FETs. |
| Large-Scale Arrays | Plates/Wafers up to 125 mm (PCD) | Enables the scaling of TeraFET designs from research prototypes to commercial sub-THz communication arrays. |
| Variable Thickness | SCD/PCD thickness from $0.1 \text{ ”m}$ to $500 \text{ ”m}$ | Allows engineers to select the optimal diamond layer thickness for thermal management and integration with underlying device structures. |
Engineering Support
Section titled âEngineering SupportâThe successful implementation of p-diamond TeraFETs relies heavily on precise material engineering, particularly controlling doping profiles and surface quality.
- Material Selection for THz Projects: 6CCVDâs in-house PhD team specializes in MPCVD growth parameters and can assist researchers in selecting the optimal Boron-Doped Diamond (BDD) grade to achieve the high momentum relaxation time ($\tau$) and high mobility required for resonant THz detection.
- Cryogenic Operation Optimization: We provide consultation on material specifications tailored for enhanced performance at cryogenic temperatures (77 K), leveraging the substantial mobility increase observed in the research.
- Advanced Processing Integration: Our team offers technical guidance on integrating diamond substrates with advanced lithography and metalization techniques necessary for realizing the high-performance, small-feature-size (20 nm) devices demonstrated in this paper.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
p-diamond field effect transistors (FETs) featuring large effective mass,\nlong momentum relaxation time and high carrier mobility are a superb candidate\nfor plasmonic terahertz (THz) applications. Previous studies have shown that\np-diamond plasmonic THz FETs (TeraFETs) could operate in plasmonic resonant\nmode at a low frequency window of 200 GHz to ~600 GHz, thus showing promising\npotential for beyond 5G sub-THz applications. In this work, we explore the\nadvantages of p-diamond transistors over n-diamond, Si, GaN and InGaAs TeraFETs\nand estimate the minimum mobility required for the resonant plasmons. Our\nnumerical simulation shows that the p-diamond TeraFET has a relatively low\nminimum resonant mobility, and thus could enable resonant detection. The\ndiamond response characteristics can be adjusted by changing operating\ntemperature. A decrease of temperature from 300 K to 77 K improves the\ndetection performance of TeraFETs. At both room temperature and 77 K, the\np-diamond TeraFET presents a high detection sensitivity in a large dynamic\nrange. When the channel length is reduced to 20 nm, the p-diamond TeraFET\nexhibits the highest DC response among all types of TeraFETs in a large\nfrequency window.\n