2.1 W/mm Output Power Density at 10 GHz for H-Terminated Diamond MOSFETs With (111)-Oriented Surface
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-12-25 |
| Journal | IEEE Journal of the Electron Devices Society |
| Authors | Bing Qiao, Pengfei Dai, Xinxin Yu, Zhonghui Li, Ran Tao |
| Institutions | Nanjing Institute of Technology |
| Citations | 3 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Performance (111)-Oriented Diamond MOSFETs
Section titled âTechnical Documentation & Analysis: High-Performance (111)-Oriented Diamond MOSFETsâThis document analyzes the research demonstrating a record 2.1 W/mm output power density at 10 GHz using H-terminated diamond MOSFETs fabricated on (111)-oriented single-crystal diamond (SCD) substrates. This achievement validates the superior performance of the (111) orientation for high-frequency, high-power radio frequency (RF) applications, directly aligning with 6CCVDâs core capabilities in advanced MPCVD diamond material supply.
Executive Summary
Section titled âExecutive SummaryâThe following points summarize the critical findings and material requirements for achieving record RF performance in H-terminated diamond MOSFETs:
- Record Power Density: A record high output power density of 2.1 W/mm was achieved at 10 GHz, significantly surpassing previous results on (001)-oriented diamond (1.26 W/mm).
- Critical Material Orientation: The use of (111)-oriented Single Crystal Diamond (SCD) was identified as the key factor, benefiting from a higher C-H dipole charge density.
- Enhanced 2DHG Channel: The (111) orientation resulted in a maximum 2DHG sheet density of 1.0 x 1013 cm-2 and a corresponding mobility of 104 cm2/V·s.
- Improved DC Performance: The device exhibited excellent DC characteristics, including a high drain current density (750 mA/mm) and a low on-resistance (24 Ω·mm).
- Low Contact Resistance: A dramatically reduced specific ohmic contact resistance (3.23 x 10-7 Ω·cm2) was achieved on the (111) surface, crucial for high-speed operation.
- Advanced Fabrication: The device utilized a robust bi-layer passivation stack (ALD Al2O3 / PECVD Si3N4) and T-shaped gate metalization (Ti/Au) to ensure high breakdown voltage (117 V).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Record Output Power Density | 2.1 | W/mm | At 10 GHz, VDS = -30 V |
| Drain Current Density (IDS) | 750 | mA/mm | At VGS = -6 V |
| On-Resistance (Ron) | 24 | Ω·mm | Gate length LG = 0.5 ”m |
| Breakdown Voltage (Vbr) | 117 | V | Off-state (VGS = 18 V) |
| Cutoff Frequency (fT) | 13 | GHz | Extrinsic measurement |
| Maximum Oscillation Frequency (fmax) | 28 | GHz | Extrinsic measurement |
| 2DHG Sheet Density (ps) | 1.0 x 1013 | cm-2 | Maximum, at VGS = -8 V |
| 2DHG Mobility (”ch) | 104 | cm2/V·s | Corresponding to max ps |
| Ohmic Contact Resistance (Rc) | 0.5 | Ω·mm | H-terminated (111) surface |
| Specific Contact Resistance (Ïc) | 3.23 x 10-7 | Ω·cm2 | Order of magnitude reduction vs. previous work |
| Substrate Orientation | (111) | N/A | Single Crystal Diamond (SCD) |
| Substrate Dimensions | 5 x 5 x 0.4 | mmÂł | Used for device fabrication |
| Surface Roughness (RMS) | ~1 | nm | Required for high-quality interface |
Key Methodologies
Section titled âKey MethodologiesâThe high-performance H-diamond MOSFET fabrication relied on precise material preparation and advanced deposition techniques:
- Substrate Selection: Utilization of a high-quality (111)-oriented Single Crystal Diamond (SCD) substrate (5 x 5 x 0.4 mmÂł) with a surface Root Mean Square (RMS) roughness of approximately 1 nm.
- Hydrogen Termination: Performed using a Microwave Plasma Chemical Vapor Deposition (MPCVD) system at 700 °C, 2.2 kW power, for 10 minutes to create high-density C-H bonds.
- Ohmic Contact Formation: 50 nm thick Au film deposited by Electron Beam Evaporation (EBE) and patterned via wet etching (KI/I2 solution).
- Device Isolation: Achieved by converting C-H bonds to C-O bonds via oxygen plasma treatment (300 W, 5 minutes) in unmasked regions.
- Bi-layer Passivation (Gate Dielectric):
- Al2O3 Layer: 50 nm thick layer deposited by Atomic Layer Deposition (ALD) at 350 °C.
- Si3N4 Layer: 100 nm thick secondary passivation layer deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) at 250 °C.
- T-Shaped Gate Fabrication: Defined using a two-step Electron Beam Lithography (EBL) process.
- Metalization: A 20/500 nm Ti/Au metal stack was deposited for both the T-shaped gate and the final source/drain/gate pads.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research confirms that the future of high-power RF electronics relies on high-quality, orientation-specific diamond substrates. 6CCVD is uniquely positioned to supply the necessary materials and customization services required to replicate and advance this groundbreaking work.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the performance metrics demonstrated in this paper, researchers require the highest quality SCD material with precise orientation control:
- Optical Grade Single Crystal Diamond (SCD): 6CCVD provides high-purity SCD necessary for high-performance electronic devices, ensuring minimal defects that could impede carrier transport or reduce breakdown voltage.
- Specified (111) Orientation: The core finding of this paper is the superiority of the (111) surface. 6CCVD offers SCD substrates specified to the (111) orientation, crucial for maximizing 2DHG density and achieving low on-resistance.
- Ultra-Low Surface Roughness: The paper cited an RMS roughness of ~1 nm. 6CCVD guarantees Ra < 1 nm polishing capability for SCD, ensuring the pristine surface quality required for high-integrity gate dielectric deposition (ALD Al2O3) and optimal 2DHG channel formation.
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs in-house manufacturing capabilities directly address the specific dimensional and metalization needs of advanced RF device fabrication:
| Requirement from Paper | 6CCVD Capability | Benefit to Customer |
|---|---|---|
| Substrate Dimensions | Custom plates/wafers up to 125mm (PCD) and custom SCD plates. | Ability to scale the successful 5 x 5 mmÂł prototype to larger, production-ready formats. |
| Thickness Control | SCD thickness from 0.1 ”m up to 500 ”m. | Precise control over active layer thickness for optimal thermal management and device design. |
| Metalization Stack | Internal capability for Au, Pt, Pd, Ti, W, Cu stacks. | Direct replication or optimization of the critical Ti/Au gate and pad metalization used in this study. |
| T-Gate Definition | Advanced laser cutting and patterning services. | Assistance in defining complex features like the T-shaped gates and source/drain contact windows. |
| Global Logistics | Global shipping (DDU default, DDP available). | Ensures rapid and reliable delivery of custom materials worldwide for time-sensitive research projects. |
Engineering Support
Section titled âEngineering Supportâ6CCVD maintains an in-house team of PhD-level material scientists and engineers specializing in MPCVD diamond growth and characterization.
- Material Selection for RF: Our experts can assist researchers in selecting the optimal diamond grade, orientation ((111) vs. (001)), and doping profile (H-termination vs. Boron-Doped Diamond (BDD)) for similar High-Frequency/High-Power RF MOSFET projects.
- Process Optimization: Consultation services are available to optimize surface preparation (e.g., hydrogenation recipes) to maximize 2DHG formation and minimize ohmic contact resistance, leveraging the low Rc achieved in this work.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
This paper presents high performance hydrogen-terminated diamond MOSFETs fabricated on a (111)-oriented single-crystal diamond substrate. The diamond surface was passivated by a high-quality Al2O3 grown by ALD at 350°C as well as a secondary passivation layer Si3N4 deposited by PECVD. After passivation, a low ohmic contact resistance <inline-formula> <tex-math notation=âLaTeXâ>$R_{c}$ </tex-math></inline-formula> of <inline-formula> <tex-math notation=âLaTeXâ>$0.5 \Omega \cdot $ </tex-math></inline-formula>mm was obtained and the 2DHG sheet density was as high as <inline-formula> <tex-math notation=âLaTeXâ>$1.0\times 10,,^{\mathrm{ 13}},,{\mathrm{ cm}}^{-2}$ </tex-math></inline-formula> with a corresponding mobility of <inline-formula> <tex-math notation=âLaTeXâ>$104 {\mathrm{ cm}}^{2} /\text{V}\cdot \text{s}$ </tex-math></inline-formula>. The fabricated diamond MOSFET with gate length of <inline-formula> <tex-math notation=âLaTeXâ>$0.5 ~\mu \text{m}$ </tex-math></inline-formula> showcased a high current density of 750 mA/mm, a low on-resistance of <inline-formula> <tex-math notation=âLaTeXâ>$24 \Omega \cdot $ </tex-math></inline-formula>mm, and a high off-state breakdown voltage of 117 V. Thanks to the high current density and low on-resistance, a record high output power density of 2.1 W/mm was achieved at 10 GHz with drain biased at a low voltage of −30 V. These results demonstrate that the output current and output power can be improved by using a (111)-oriented diamond, which is benefit for high-frequency and high-power RF devices.