Abstract
Ultra-thin two-dimensional semiconducting crystals in their monolayer and few-layer forms show promising aspects in nanoelectronic applications. However, the ultra-thin nature of two-dimensional crystals inevitably results in high contact resistance from limited channel/contact volume as well as device-to-device variability, which seriously limit reliable applications using two-dimensional semiconductors. Here, we incorporate rather thick two-dimensional layered semiconducting crystals for reliable vertical diodes showing excellent Ohmic and Schottky contacts. Using the vertical transport of WSe2, we demonstrate devices which are functional at various frequency ranges from megahertz AM demodulation of audio signals, to gigahertz rectification for fifth-generation wireless electronics, to ultraviolet–visible photodetection. The WSe2 exhibits an excellent Ohmic contact to bottom platinum electrode with record-low contact resistance (~50 Ω) and an exemplary Schottky junction to top transparent conducting oxide electrode. Our semitransparent vertical WSe2 Schottky diodes could be a key component of future high frequency electronics in the era of fifth-generation wireless communication.
Highlights
Ultra-thin two-dimensional semiconducting crystals in their monolayer and few-layer forms show promising aspects in nanoelectronic applications
In a vertical diode, relatively thick transition metal dichalcogenides (TMDs) can serve as an ideal platform for achieving ultra-low contact resistance and capacitance
The full depletion thickness (Xd) of the diodes under reverse bias would approach to the physical thickness of WSe2 flake, and it is estimated from saturated Cj value (= εWSe2Aj/Xd; εWSe2 is the dielectric constant of 7.9εo and Aj is the junction area of 2.02 × 10–6 cm2)[38,39,40]
Summary
Ultra-thin two-dimensional semiconducting crystals in their monolayer and few-layer forms show promising aspects in nanoelectronic applications. Equipped with practically facile fabrication process using thick and large-area van der Waals TMD crystals, our vertical TMD Schottky diodes exhibit high device stability and reproducibility Such vertical Schottky or PN diodes have been well known in conventional semiconductor materials, among which the highest frequencies come from single-crystalline Si and GaAs. according to Supplementary Table 1, other thin-film-based candidates might not be able to exceed fifth-generation (5G) compatible frequencies higher than 20 GHz. We believe that our semitransparent WSe2 Schottky diode would find breakthroughs in perspectives of future 5G communications and automobile electronics toward high frequency (K-band: 18–27 GHz) applications[32,33]
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