Hydrogen-terminated and oxygen-terminated diamond metal-oxide-semiconductor field-effect transistors
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-09-02 |
| Journal | Functional Diamond |
| Authors | Jiangwei Liu |
| Institutions | National Institute for Materials Science |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis review article details the fabrication and performance of diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) based on both hydrogen-terminated (H-diamond) and boron-doped oxygen-terminated (O-diamond) channels, targeting high-power, high-frequency, and high-temperature applications.
- E-mode H-Diamond Achievement: Successful fabrication of enhancement-mode (E-mode) H-diamond MOSFETs, crucial for logic circuits, achieved through specific bilayer gate oxide deposition (Sputtering/ALD) and subsequent annealing (150-350 °C).
- Logic Circuit Demonstration: Functional H-diamond MOSFET NOT and NOR logic circuits were demonstrated, exhibiting robust logical properties and high gain (up to 26.1 for NOT circuit at VDD = -25.0 V).
- High-Temperature Operation (O-Diamond): Boron-doped O-diamond MOSFETs demonstrated efficient operation up to 300 °C, leveraging the materialâs thermal stability and enhanced boron dopant activation at elevated temperatures.
- Record On/Off Ratio: The O-diamond MOSFETs achieved an on/off current ratio exceeding 109, the highest reported value to date for this device type, confirming excellent switching capability.
- Performance Trade-offs: While E-mode H-diamond MOSFETs showed slightly lower maximum drain current (ID,max) compared to D-mode devices, the maximum extrinsic transconductance (gm,max) remained nearly identical (17 mS/mm).
- Thermal Advantage: At 300 °C, the O-diamond MOSFET ID,max increased substantially (from -1.2 mA/mm at RT to -10.9 mA/mm) and the on-resistance (RON) dropped significantly (from 9.6 kΩ mm to 1.1 kΩ mm).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Band Gap | 5.47 | eV | Intrinsic material property |
| Boron Activation Energy | 0.37 | eV | O-diamond channel layer |
| H-Diamond ID,max (D-mode) | -112.4 | mA/mm | Al2O3/H-diamond MOSFET |
| H-Diamond RON (D-mode) | 56.0 | Ω mm | Al2O3/H-diamond MOSFET (VGS = -10.0 V) |
| H-Diamond VTH (D-mode) | 5.3 ± 0.1 | V | Al2O3/H-diamond MOSFET |
| H-Diamond ID,max (E-mode) | -69.3 | mA/mm | LaAlO3/Al2O3/H-diamond MOSFET |
| H-Diamond VTH (E-mode) | -5.0 ± 0.1 | V | LaAlO3/Al2O3/H-diamond MOSFET |
| H-Diamond gm,max (D/E-mode) | 17 | mS/mm | Both D-mode and E-mode devices |
| H-Diamond NOT Circuit Gain | 26.1 | N/A | Maximum gain at VDD = -25.0 V |
| O-Diamond ID,max (RT) | -1.2 | mA/mm | In-situ annealed (300 °C) device |
| O-Diamond ID,max (300 °C) | -10.9 | mA/mm | In-situ annealed (300 °C) device |
| O-Diamond RON (RT) | 9.6 | kΩ mm | In-situ annealed (300 °C) device |
| O-Diamond RON (300 °C) | 1.1 | kΩ mm | In-situ annealed (300 °C) device |
| O-Diamond On/Off Ratio | > 109 | N/A | Highest reported value for O-diamond MOSFETs |
| O-Diamond VTH (RT) | 63.8 ± 0.1 | V | In-situ annealed (300 °C) device |
| O-Diamond VTH (300 °C) | 31.2 ± 0.1 | V | In-situ annealed (300 °C) device |
| H-Diamond 2DHG Density | 1012 to 1014 | cm-2 | Sheet hole density on H-diamond surface |
Key Methodologies
Section titled âKey MethodologiesâThe research focused on controlling the channel layer properties and gate oxide interfaces through specific deposition and thermal treatments to achieve desired device modes (D-mode vs. E-mode) and high-temperature stability.
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H-Diamond E-mode Fabrication:
- Gate Oxide: Utilization of a bilayer gate oxide structure (e.g., SD-LaAlO3/ALD-Al2O3).
- Annealing: Post-deposition annealing was performed in the temperature range of 150-350 °C. This step is critical for eliminating negative acceptors or introducing compensatory positive charges at the interface, thereby reducing hole density and inducing E-mode characteristics.
- Logic Circuits: NOT and NOR logic circuits were constructed using a combination of D-mode (ALD-Al2O3/H-diamond) MOSFETs as the load device and E-mode (SD-LaAlO3/ALD-Al2O3/H-diamond) MOSFETs as the driver device.
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O-Diamond High-Temperature Fabrication:
- Channel Layer: Boron-doped O-diamond channel layer was used, which inherently lacks the surface thermal sensitivity issues of H-diamond.
- Ex-situ Annealing: Devices were annealed ex-situ at 500 °C for 30 minutes to investigate thermal effects on performance metrics like RON and ID,max.
- In-situ Annealing (Reliability Enhancement): Devices were operated and characterized during in-situ annealing at 300 °C. A 20 nm-thick Al2O3 cover layer was applied to the sample surface to eliminate environmental effects and edge leakage, enhancing reliability and performance.
- Performance Improvement Strategy: Future improvements focus on reducing Ohmic contact resistance (via heavy B-doping or ion implantation) and minimizing device dimensions (LG, LS-G, LD-G) to further lower RON.
Commercial Applications
Section titled âCommercial ApplicationsâThe exceptional properties of diamond MOSFETsâlarge band gap, high breakdown field, high carrier mobility, and high thermal conductivityâmake them ideal for next-generation electronics in demanding environments.
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High-Power Electronics:
- Application: Power converters, inverters, and switches operating at high voltages (breakdown voltage up to 4266 V reported in related work).
- Value Proposition: Diamond devices offer superior efficiency and smaller form factors compared to silicon or SiC devices.
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High-Frequency (RF) Communications:
- Application: High-speed signal processing, high-frequency wireless communications, and radar systems.
- Value Proposition: The high cut-off frequency (fT) and maximum oscillation frequency (fmax) (up to 70/80 GHz reported) enable high-speed operation.
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Extreme Environment Electronics:
- Application: Devices for use in high-temperature environments (e.g., automotive, aerospace, geothermal drilling) and radiation-rich environments (e.g., nuclear facilities, space).
- Value Proposition: O-diamond MOSFETs maintain functionality and show improved performance (lower RON, higher ID,max) at temperatures up to 300 °C due to enhanced dopant activation.
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Advanced Computing and Logic:
- Application: High-speed logic circuits (NOT, NOR gates) and complementary metal-oxide-semiconductor (CMOS) devices.
- Value Proposition: Successful demonstration of functional E-mode and D-mode logic circuits paves the way for diamond-based integrated circuits.
View Original Abstract
Extensive research has been conducted on wide-bandgap semiconductor diamond for the advancement of high-power, high-frequency, and high-temperature electronic devices. The author has established long-term collaboration with Prof. Koide, focusing on producing p-type hydrogen-terminated diamond (H-diamond) and boron-doped oxygen-terminated diamond (O-diamond) based metal-oxide-semiconductor field-effect transistors (MOSFETs). This article presents our primary research findings on the fabrication of enhancement-mode H-diamond MOSFETs and MOSFET logic circuits, as well as the high-temperature operation of the boron-doped O-diamond MOSFETs.