Black Phosphorus Radio-Frequency Transistors
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Abstract
Few-layer
and thin film forms of layered black phosphorus (BP) have recently
emerged as a promising material for applications in high performance nanoelectronics and infrared
optoelectronics. Layered BP thin films offer a moderate bandgap of
around 0.3 eV and high carrier mobility, which lead to transistors
with decent on–off ratios and high on-state current densities.
Here, we demonstrate the gigahertz frequency operation of BP field-effect
transistors for the first time. The BP transistors demonstrated here
show respectable current saturation with an on–off ratio that
exceeds 2 × 10<sup>3</sup>. We achieved a current density in
excess of 270 mA/mm and DC transconductance above 180 mS/mm for hole
conduction. Using standard high frequency characterization techniques,
we measured a short-circuit current-gain cutoff frequency <i>f</i><sub>T</sub> of 12 GHz and a maximum oscillation frequency <i>f</i><sub>max</sub> of 20 GHz in 300 nm channel length devices.
BP devices may offer advantages over graphene transistors for high
frequency electronics in terms of voltage and power gain due to the
good current saturation properties arising from their finite bandgap,
thus can be considered as a promising candidate for the future high
performance thin film electronics technology for operation in the
multi-GHz frequency range and beyond