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The ohmic contact resistance (${R}_{C}$), surface resistance (${R}_{S}$), and channel resistance (${R}_{\text {CH}}$) of hydrogen-terminated diamond (H-diamond) MOSFETs were investigated in this study. Planar-type and T-type H-diamond MOSFETs were employed to analyze them. Because no interspaces exist between the source–drain and gate electrodes for the T-type H-diamond MOSFETs, then ${R}_{S}$ is zero. Both planar-type and T-type MOSFETs show low leakage current densities and good operations. By considering the relationships between the total resistance (${R}_{ \mathrm{\scriptscriptstyle ON}}$) and 1/ $\vert $ gate voltage-threshold voltage $\vert $ , ${R}_{C}$ and ${R}_{\text {CH}}$ for the T-type H-diamond MOSFET at a gate voltage of −10.0 V are determined to be 13.8 and 21.8 $\Omega \cdot $ mm, respectively. As ${R}_{C}$ for both MOSFETs is the same, ${R}_{S}$ and ${R}_{\text {CH}}$ for the planar-type H-diamond MOSFET are deduced to be 90.0 and 15.8 $\Omega \cdot $ mm, respectively. ${R}_{S}$ accounts for 75.3% of ${R}_{ \mathrm{\scriptscriptstyle ON}}$ for the planar-type H-diamond MOSFET, which is the main reason for its lower drain current and extrinsic transconductance than those of the T-type MOSFET. Although ${R}_{S}$ is suppressed for the T-type H-diamond MOSFET, ${R}_{C}$ occupies 38.8% of ${R}_{ \mathrm{\scriptscriptstyle ON}}$. To further improve the performance of the H-diamond MOSFETs, it is important to eliminate ${R}_{S}$ and decrease ${R}_{C}$ to further improve the electrical properties of the H-diamond MOSFETs. [ABSTRACT FROM AUTHOR]

Boron-doped diamond (B-diamond) metal–oxide–semiconductor (MOS) capacitor and MOS field-effect transistor (MOSFET) are fabricated on a flat diamond epitaxial layer. Their electrical properties and thermal stabilities after annealing at 500 °C are investigated. Annealing makes the leakage current density of the B-diamond MOS capacitor increase slightly. There is a larger stretch-out for the capacitance-voltage curve in the depletion region after annealing than that before annealing. The drain-current maxima for the as-fabricated and 500 °C-annealed MOSFETs are obtained as −0.49 and −0.60 mA/mm, respectively. Extrinsic transconductance maxima are 18.7 and $21.4~\mu \text{S}$ /mm, respectively. These obtained values are considerably larger than those obtained by the previously reported B-diamond MOSFETs. [ABSTRACT FROM AUTHOR]

Here, thermal stabilities for Ohmic contact properties of Pt, Au, and Pd on the same hydrogen-terminated diamond (H-diamond) epitaxial layer are investigated. A long-term annealing process is performed with an annealing temperature and time of 400 °C and 8 h, respectively. Before annealing, good Ohmic contact properties are observed for only two contacts of the Pt/H-diamond and Pd/H-diamond with specific contact resistivity (ρC) values of 2.7 × 10−3 Ω cm2 and 2.6 × 10−4 Ω cm2, respectively. After long-term annealing, all three contacts on the H-diamond show good Ohmic contact properties. The ρC values for the Pt/H-diamond and Au/H-diamond are 3.1 × 10−2 Ω cm2 and 4.2 × 10−4 Ω cm2, respectively. They are higher than that of the Pd/H-diamond (1.1 × 10−4 Ω cm2). Therefore, low ρC and good thermal stability for the Pd/H-diamond are achieved. This is meaningful for pushing forward the development of H-diamond-based electronic devices for high-temperature applications. [ABSTRACT FROM AUTHOR]

In this article, we report the fabrication and characterization of boron-doped diamond (B-diamond) Schottky diodes and MESFETs. Effects of annealing at 573–973 K on the electrical properties of these devices are investigated. Current density maximum for the as-fabricated Schottky diode is 0.05 A/cm2 at a gate voltage of −10.0 V. Annealing at 673 and 973 K makes it increase first to 0.70 A/cm2 and decrease lately to 0.07 A/cm2, respectively. ON/OFF ratios for the as-fabricated B-diamond Schottky diode exceed 4.5 × 108 at the OFF-voltage (VOFF) of 0 V and 3.2 × 106 at VOFF = 42.0 V. For the annealed Schottky diode, the ON/OFF ratios are higher than 1.7 × 106 at VOFF < 6.0} V. Ideality factor and barrier height for Au/Pt bilayer gates on the B-diamond channel layer range from 1.05 to 1.78 and from 1.24 to 1.56 eV, respectively. All three B-diamond MESFETs with the gate lengths of 12.0, 7.0, and 4.3 μm, respectively, operate with p-type channel characteristics. The drain current maxima for the as-fabricated MESFETs are −0.11, −0.16, and −0.39 mA/mm. After annealing at 773 K, these values increase to −0.17, −0.24, and −0.55 mA/mm. Annealing at 773 K also increases the extrinsic transconductance maxima for the three MESFETs from 11.1, 11.0, and 10.4μS/mm to 18.6, 16.2, and 14.4 μS/mm, respectively. [ABSTRACT FROM AUTHOR]

Ta2O5 films have been deposited on hydrogen-terminated diamond (H-diamond) by a radio-frequency sputter-deposition technique at room temperature. Electronic band structure of Ta2O5/H-diamond heterojunction has been investigated by X-ray photoelectron spectroscopy. Based on the binding energies of core-levels and valence band maximum values, valence band offset has been found to be 1.5±0.2eV for the Ta2O5/H-diamond heterointerface. It shows a type-II band configuration with conduction band offset of 2.4±0.2eV. The large ΔEV value makes the Ta2O5/H-diamond heterojunction probably suitable for the application of high power and high frequency field effect transistors. [ABSTRACT FROM AUTHOR]

Thanks to its excellent intrinsic properties, diamond is promising for applications of high-power electronic devices, ultraviolet detectors, biosensors, high-temperature tolerant gas sensors, etc. Here, an overview of high-k oxides on hydrogenated-diamond (H-diamond) for metal-oxide-semiconductor (MOS) capacitors and MOS field-effect transistors (MOSFETs) is demonstrated. Fabrication routines for the H-diamond MOS capacitors and MOSFETs, band configurations of oxide/H-diamond heterointerfaces, and electrical properties of the MOS and MOSFETs are summarized and discussed. High-k oxide insulators are deposited using atomic layer deposition (ALD) and sputtering deposition (SD) techniques. Electrical properties of the H-diamond MOS capacitors with high-k oxides of ALD-Al2O3, ALD-HfO2, ALD-HfO2/ALD-Al2O3 multilayer, SD-HfO2/ALD-HfO2 bilayer, SD-TiO2/ALD-Al2O3 bilayer, and ALD-TiO2/ALD-Al2O3 bilayer are discussed. Analyses for capacitance-voltage characteristics of them show that there are low fixed and trapped charge densities for the ALD-Al2O3/H-diamond and SD-HfO2/ALD-HfO2/H-diamond MOS capacitors. The k value of 27.2 for the ALD-TiO2/ALD-Al2O3 bilayer is larger than those of the other oxide insulators. Drain-source current versus voltage curves show distinct pitch-off and p-type channel characteristics for the ALD-Al2O3/H-diamond, SD-HfO2/ALD-HfO2/H-diamond, and ALD-TiO2/ALD-Al2O3/H-diamond MOSFETs. Understanding of fabrication routines and electrical properties for the high-k oxide/H-diamond MOS electronic devices is meaningful for the fabrication of high-performance H-diamond MOS capacitor and MOSFET gas sensors. [ABSTRACT FROM AUTHOR]

The authors report on the direct integration of high-dielectric constant (high-k) Ta2O5 films on p-type single crystal diamond for high-power electronic devices. Crystallized hexagonal phase δ-Ta2O5 film is achieved on diamond by annealing the amorphous Ta2O5 film deposited by a sputter-deposition technique. The electrical properties of the Ta2O5 thin films are investigated by fabricating metal-insulator-semiconductor (MIS) diodes. The leakage current of the MIS diode is as low as 10-8 A/cm2 for the as-deposited amorphous Ta2O5 film and 10-2 A/cm2 for the crystallized film, which is 108 and 102 times lower than that of the Schottky diode at a forward bias of -3 V, respectively. The dielectric constant of the amorphous Ta2O5 films is measured to be 16 and increases to 29 after annealing at 800 °C. Different current leakage mechanisms and charge trapping behaviors are proposed for the amorphous and crystallized Ta2O5 thin films. [ABSTRACT FROM AUTHOR]