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Ultrafast van der Waals diode using graphene quantum capacitance and Fermi-level depinning.
Sungjae Hong1, Chang-Ui Hong2, Sol Lee1,3
1Department of Physics, Van der Waals Materials Research Center, Yonsei University, Seoul 03722, Republic of Korea.
Science Advances
|July 19, 2023
Summary
Graphene insertion in vertical diodes significantly boosts performance at ultrahigh frequencies. This enhancement is due to graphene
Area of Science:
- Materials Science
- Electrical Engineering
- Condensed Matter Physics
Background:
- Graphene's electrical properties make it useful in stacked devices.
- Its role in metal-semiconductor junctions is known for low frequencies.
- High-frequency applications of graphene insertion are underexplored.
Purpose of the Study:
- Investigate graphene's impact on vertical diodes at ultrahigh frequencies.
- Demonstrate diode operation using MoSe2 and graphene.
- Analyze the frequency-dependent behavior of graphene-semiconductor interfaces.
Main Methods:
- Fabrication of vertical Pt/n-MoSe2/graphene/Au diode structures.
- Measurement of device performance up to ~200 GHz.
- Analysis of charge transport mechanisms and capacitance effects.
Main Results:
- Achieved diode operation at ~200 GHz cutoff frequency (fC).
- Graphene's charge modulation freezes above a few GHz due to quantum capacitance.
- Transformed Ohmic graphene/MoSe2 junction to a pinning-free Schottky junction.
- Significantly reduced total capacitance compared to devices without graphene.
Conclusions:
- Graphene insertion enhances ultrahigh-frequency diode performance.
- The quantum capacitance effect is key to high-frequency operation.
- Graphene is a promising material for high-frequency electronic devices.
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