Work Function Tailoring of Carbon-Added Tungsten Gate Electrodes

Lin, Chun‐Min; Shen, Shu-Hua; Chen, Jen‐Sue

doi:10.1149/1.3524268

Cited by 11 publications

(4 citation statements)

References 25 publications

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“…"#$ , where χAlGaN is the value of the electron affinity for an AlGaN layer with 26% Al content. For the WC, a work function of 5.2 eV can be estimated [40,41]. In this condition, an ideal barrier height of 1.1 eV is expected, which is much higher than that obtained by the fit of experimental J-V curves.…”

Section: Resultsmentioning

confidence: 86%

“…The theoretical barrier height value Φ B for an ideal WC/AlGaN interface depends on the WC work function Φ m(WC) according to the Schottky-Mott relation Φ B = Φ m(WC) − χ AlGaN , where χ AlGaN is the value of the electron affinity for an AlGaN layer with 26% Al content. For the WC, a work function of 5.2 eV can be estimated [42,43]. In this condition, an ideal barrier height of 1.1 eV is expected, which is much higher than that obtained by the fit of the experimental J-V curves.…”

Section: Resultsmentioning

confidence: 86%

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Thermal annealing effect on electrical and structural properties of Tungsten Carbide Schottky contacts on AlGaN/GaN heterostructures

Greco

Franco

Bongiorno

et al. 2020

Semicond. Sci. Technol.

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Tungsten carbide (WC) contacts have been investigated as a novel gold-free Schottky metallization for AlGaN/GaN heterostructures. The evolution of the electrical and structural/compositional properties of the WC/AlGaN contact has been monitored as a function of the annealing temperature in the range from 400 to 800°C. The Schottky barrier height (ΦB) at WC/AlGaN interface, extracted from the forward current-voltage characteristics of the diode, decreased from ∼0.8 eV in the asdeposited and 400°C annealed sample, to 0.56 eV after annealing at 800 °C. This large reduction of ΦB was accompanied by a corresponding increase of the reverse bias leakage current. Transmission electron microscopy coupled to electron energy loss spectroscopy analyses revealed the presence of oxygen (O) uniformly distributed in the WC layer, both in the as-deposited and 400°C annealed sample. Conversely, oxygen accumulation in a 2-3 nm thin W-O-C layer at the interface with AlGaN was observed after the annealing at 800 °C, as well as the formation of W2C grains within the film (confirmed by X-ray diffraction analyses). The formation of this interfacial W-O-C layer is plausibly the main origin of the decreased ΦB and the increased leakage current in the 800°C annealed Schottky diode, whereas the decreased O content inside the WC film can explain the reduced resistivity of the metal layer. The results provide an assessment of the processing conditions for the application of WC as Schottky contact for AlGaN/GaN heterostructures.

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Section: Resultsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 86%

Thermal annealing effect on electrical and structural properties of Tungsten Carbide Schottky contacts on AlGaN/GaN heterostructures

Greco

Franco

Bongiorno

et al. 2020

Semicond. Sci. Technol.

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“…The work function of steel, tungsten, and copper was 4.5, 4.55, and 4.65 eV, respectively [22]. The work function of tungsten carbide was 4.32-4.82 eV [23]. As known, the work function determines the electron emission ability on the cathode surface.…”

Section: Discharge Probability Of Conventional Lc Generator Using Dif...mentioning

confidence: 99%

Realization of high discharge frequency in LC pulse generator for EDM by ignition using transistor circuit

Lin

Kunieda

2023

Int J Adv Manuf Technol

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Recent research has revealed that the LC pulse generator is able to generate higher rising speed discharge current pulses and high open voltage for EDM by utilizing electromotive force induced by an inductor. However, the discharge probability of LC generators is low because the duration of the open voltage pulse is significantly short in the order of several microseconds, although it usually takes several microseconds or longer for discharge to be ignited. In this paper, the discharge probability of the LC pulse generator was investigated, which was proved to be lower than 20% if the discharge frequency divided by the switching frequency of the LC generator is defined as the discharge probability of the LC generator. An excessively short delay time demonstrates that the gap will be short-circuited, resulting in decreased machining stability. Hence, this paper proposes a modified version of the LC generator, combining a high impedance transistor pulse generator with a conventional LC pulse generator. The high impedance transistor pulse generator is used to cause the ignition in the interelectrode gap, but not to supply energy to remove the workpiece. Triggered by the ignition, the LC pulse generator is activated to supply high discharge energies and unique discharge current shape. This modified LC pulse generator can produce a discharge frequency 2 to 3 times higher than the conventional LC pulse generator.

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“…The work function of steel, tungsten and copper was 4.5, 4.55 and 4.65eV, respectively [25]. The work function of tungsten carbide was 4.32-4.82eV [26]. As known, the work function determines the electron emission ability on the cathode surface.…”

Section: Discharge Probability Of Conventional Lc Generator Under Dif...mentioning

confidence: 99%

Realization of high discharge frequency in LC pulse generator for EDM by ignition using transistor circuit

Lin

Kunieda²

2022

Preprint

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This paper aims to design a novel pulse generator for electrical discharge machining (EDM) which can generate discharge current pulse with high discharge frequency more efficiently. Recent research has revealed that the LC pulse generator is able to generate higher rising speed discharge current pulses and high open voltage for EDM by utilizing electromotive force induced by an inductor. Conventional LC generators use inductors to store energy and switches to control the open gap voltage and discharge current flowing through the gap by varying the charging time of inductance, thereby realizing higher peak discharge power even with a low voltage DC power supply, as well as large removal volume per discharge due to high rising speed waveforms. However, the discharge probability of LC generators is lower than 20% if the discharge frequency divided by the switching frequency of the LC generator is defined as the discharge probability of the LC generator. This is because the duration of the open voltage pulse is significantly short in the order of several microseconds, although it usually takes several microseconds or longer for discharge to be ignited. This discharge delay time is an important parameter in EDM because longer delay time results in lower material removal rate, and an excessively short delay time indicates that the gap will be short circuited, resulting in decrease machining stability. Hence, this paper proposes a modified version of the LC generator in which a high impedance transistor pulse generator is used to control the discharge ignition in EDM to produce discharge frequency 2 to 3 times higher than the conventional LC pulse generator.

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Work Function Tailoring of Carbon-Added Tungsten Gate Electrodes

Cited by 11 publications

References 25 publications

Thermal annealing effect on electrical and structural properties of Tungsten Carbide Schottky contacts on AlGaN/GaN heterostructures

Thermal annealing effect on electrical and structural properties of Tungsten Carbide Schottky contacts on AlGaN/GaN heterostructures

Realization of high discharge frequency in LC pulse generator for EDM by ignition using transistor circuit

Realization of high discharge frequency in LC pulse generator for EDM by ignition using transistor circuit

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