Characteristics of H-terminated single crystalline diamond field effect transistors
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-01-01 |
| Journal | Acta Physica Sinica |
| Authors | Zeyang Ren, Jinfeng Zhang, Jincheng Zhang, Xu Sheng-Rui, Chunfu Zhang |
| Citations | 4 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: H-Terminated Single Crystal Diamond MESFETs
Section titled âTechnical Documentation & Analysis: H-Terminated Single Crystal Diamond MESFETsâThis document analyzes the research paper âCharacteristics of H-terminated single crystalline diamond field effect transistorsâ (Acta Physica Sinica, 2017) to provide technical specifications and demonstrate how 6CCVDâs advanced MPCVD diamond materials and processing capabilities can support and extend this high-performance semiconductor research.
Executive Summary
Section titled âExecutive SummaryâThe research successfully demonstrates high-performance, normally-on Metal-Semiconductor Field Effect Transistors (MESFETs) utilizing a 200 nm Single Crystal Diamond (SCD) layer grown via Microwave Plasma Chemical Vapor Deposition (MPCVD) and subsequently Hydrogen (H) terminated.
- High Current Density: Achieved a saturation drain current (IDsat) of 77 mA/mm at a safe operating gate voltage (VGS = -3.5 V).
- Peak Transconductance: Demonstrated a maximum transconductance (gm) of 30 mS/mm, confirming excellent gate control over the channel.
- Material Quality Validation: The device exhibited an exceptionally high switching ratio of approximately 109, validating the high insulation quality of the MPCVD SCD layer.
- 2DHG Characteristics: Confirmed a high 2D Hole Gas (2DHG) density of $1.99 \times 10^{13}$ cm-2, which is the primary factor enabling high current output.
- Surface Morphology: The use of highly polished SCD resulted in a low RMS roughness (Ra) of 0.92 nm, crucial for maintaining carrier mobility.
- Future Direction: The study highlights the immediate need for improved gate dielectrics and enhanced carrier mobility, areas where 6CCVD offers specialized material solutions.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the key performance metrics and material parameters extracted from the MESFET device analysis:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| SCD Epitaxial Thickness | 200 | nm | Grown via MPCVD |
| Substrate Type | Ib (HPHT) | N/A | (001) Orientation |
| Gate Length (LG) | 2 | ”m | Device Dimension |
| Gate Width (WG) | 50 / 100 | ”m | Device Dimension |
| Max Saturation Current (IDsat) | 96 | mA/mm | At VGS = -6 V |
| Safe Saturation Current (IDsat) | 77 | mA/mm | At VGS = -3.5 V |
| Peak Transconductance (gm) | 30 | mS/mm | At VGS = -3.5 V |
| 2DHG Carrier Density (ps) | 1.99 x 1013 | cm-2 | Extracted from C-V data |
| Switching Ratio (Ion/Ioff) | ~109 | N/A | High insulation quality |
| RMS Roughness (Ra) | 0.92 | nm | After growth and H-termination |
| Mobility Range (”) | 6.6 - 27.0 | cm2/(V·s) | Varies with VGS |
| Gate Capacitance (Cox) | 0.588 | ”F/cm2 | Extracted from C-V data |
Key Methodologies
Section titled âKey MethodologiesâThe fabrication of the H-terminated SCD MESFET relies heavily on precise MPCVD growth and controlled surface termination processes.
- Substrate Preparation: Use of 3 mm x 3 mm (001) Type-Ib HPHT diamond substrates, followed by fine polishing (initial Ra 0.83 nm).
- Acid Cleaning/O-Termination: Substrates were cleaned in a hot H2SO4/HNO3 (1:1) mixture at 250 °C for 1 hour to remove surface contaminants and achieve Oxygen (O) termination.
- MPCVD Epitaxy: Growth of a 200 nm thick, high-quality Single Crystal Diamond (SCD) layer using MPCVD.
- Growth Parameters:
- Total Gas Flow: 500 sccm
- Methane (CH4) Concentration: 0.1%
- Pressure: 100 Torr (1.33322 x 102 Pa)
- Microwave Power: 1 kW
- Temperature: 900 °C
- Hydrogen Termination (H-Termination): Post-growth treatment in H2 plasma for 10 minutes, followed by cooling in H2 atmosphere to room temperature, creating the stable C-H surface bonds and inducing the 2DHG.
- Ohmic Contact Formation: 100 nm thick Gold (Au) layer deposited via thermal evaporation, forming ohmic contacts (Source/Drain) due to the non-pinning nature of the H-terminated surface.
- Device Isolation: Low-power Oxygen (O) plasma treatment (10 min) used to convert exposed H-terminated areas back to insulating O-terminated surfaces.
- Gate Contact Formation: 100 nm thick Aluminum (Al) layer deposited via thermal evaporation to form the Schottky gate contact.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the high-quality SCD materials and custom processing required to replicate, scale, and advance this research into commercial high-power and high-frequency diamond electronics.
| Research Requirement | 6CCVD Solution & Value Proposition |
|---|---|
| High-Quality SCD Epitaxy | Optical Grade SCD Wafers: We provide high-purity, low-defect SCD layers with thicknesses ranging from 0.1 ”m up to 500 ”m, perfectly matching the required 200 nm epitaxial layer thickness. Our MPCVD process ensures the high crystalline quality necessary for maximizing carrier lifetime and mobility. |
| Substrate Material & Size | Custom Substrates & Large Area Capability: We supply high-quality HPHT substrates (up to 10 mm thick) and offer SCD plates/wafers up to 125 mm (PCD) for scaling device fabrication. We guarantee the (001) orientation specified in the paper. |
| Ultra-Smooth Surface Quality | Precision Polishing (Ra < 1 nm): Our standard Single Crystal Diamond (SCD) polishing achieves a root mean square (Ra) roughness of less than 1 nm. This ultra-smooth surface is critical for minimizing interface scattering and maximizing 2DHG mobility, directly supporting the high-performance metrics achieved in this study. |
| Metalization Scheme (Au Ohmic, Al Gate) | Integrated Custom Metalization: The paper utilized Au and Al. 6CCVD offers in-house deposition of standard and custom metal stacks, including Au, Pt, Pd, Ti, W, and Cu. We can replicate the Au ohmic contact scheme or develop advanced Ti/Pt/Au stacks for improved thermal stability and reduced contact resistance, essential for high-power operation. |
| Applicable Materials for Extension | Optical Grade SCD for H-Termination: To replicate or extend this research, Optical Grade Single Crystal Diamond (SCD) is the explicit material requirement. For future work involving gate dielectrics (MISFETs) or alternative doping, Boron-Doped Diamond (BDD) materials are available. |
| Engineering Support | Expert Consultation: 6CCVDâs in-house PhD team specializes in wide band-gap semiconductor physics and can assist with material selection, surface termination protocols, and optimization of epitaxial recipes for similar H-terminated Diamond FET projects. |
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Diamond has been considered as an ultimate semiconductor, which has great potential applications in high power, high frequency semiconductor devices. Up to now, the twodimensional hole gas (2DHG) induced on the hydrogenterminated diamond surface is used most popularly to form electric conduction in diamond semiconductor at room temperature, due to the obstacle caused by lacking of easily-ionized dopants. A 200-nm-thick single crystalline diamond is grown by microwave plasma chemical vapor deposition on the type-Ib high-pressure high-temperature synthesized diamond substrate. Then the sample is treated in hydrogen plasma atmosphere to achieve hydrogen terminated diamond surface. The sample is characterized by X-ray photoelectron spectroscopy and atomic force microscope. After that, the normally-on hydrogen-terminated diamond field effect transistors are achieved. The device with a gate length of 2 ÎŒup m delivers a saturation leakage current of 96 mA/mm at gate voltage VGS=-6 V, at which, however, the gate leakage current is too large. The saturation current reaches 77 mA/mm at VGS=-3.5 V with safety. The device shows typical long-channel behavior. The gate voltage varies almost linearly. In the saturation region of the device, the transconductance (gm) increases near-linearly to 30 mS/mm with the increase of the gate voltage in a range of 5.9 V. Analyses of the on-resistance and capacitance-voltage (C-V) data show that the 2DHG under the gate achieves a density as high as 1.99Ă1013 cm-2, and the extracted channel carrier density and mobility are always kept increasing with VGS negatively shifting to -2.5 V. The nearlinearly increasing of gm in a large VGS range is attributed to high 2DHG density, quite a large gate capacitance (good gate control), and increased mobility. The relevant researches of improving the carrier mobility in the channel and of finding proper gate dielectrics to improve the forward gate breakdown voltage are underway.