3 research outputs found
A Dynamically Reconfigurable Ambipolar Black Phosphorus Memory Device
Nonvolatile
charge-trap memory plays an important role in many
modern electronics technologies, from portable electronic systems
to large-scale data centers. Conventional charge-trap memory devices
typically work with fixed channel carrier polarity and device characteristics.
However, many emerging applications in reconfigurable electronics
and neuromorphic computing require dynamically tunable properties
in their electronic device components that can lead to enhanced circuit
versatility and system functionalities. Here, we demonstrate an ambipolar
black phosphorus (BP) charge-trap memory device with dynamically reconfigurable
and polarity-reversible memory behavior. This BP memory device shows
versatile memory properties subject to electrostatic bias. Not only
the programmed/erased state current ratio can be continuously tuned
by the back-gate bias, but also the polarity of the carriers in the
BP channel can be reversibly switched between electron- and hole-dominated
conductions, resulting in the erased and programmed states exhibiting
interchangeable high and low current levels. The BP memory also shows
four different memory states and, hence, 2-bit per cell data storage
for both n-type and p-type channel conductions, demonstrating the
multilevel cell storage capability in a layered material based memory
device. The BP memory device with a high mobility and tunable programmed/erased
state current ratio and highly reconfigurable device characteristics
can offer adaptable memory device properties for many emerging applications
in electronics technology, such as neuromorphic computing, data-adaptive
energy efficient memory, and dynamically reconfigurable digital circuits
Large-Velocity Saturation in Thin-Film Black Phosphorus Transistors
A high
saturation velocity semiconductor is appealing for applications
in electronics and optoelectronics. Thin-film black phosphorus (BP),
an emerging layered semiconductor, shows a high carrier mobility and
strong mid-infrared photoresponse at room temperature. Here, we report
the observation of high intrinsic saturation velocity in 7 to 11 nm
thick BP for both electrons and holes as a function of charge-carrier
density, temperature, and crystalline direction. We distinguish a
drift velocity transition point due to the competition between the
electron-impurity and electron–phonon scatterings. We further
achieve a room-temperature saturation velocity of 1.2 (1.0) ×
10<sup>7</sup> cm s<sup>–1</sup> for hole (electron) carriers
at a critical electric field of 14 (13) kV cm<sup>–1</sup>,
indicating an intrinsic current-gain cutoff frequency ∼20 GHz·μm
for radio frequency applications. Moreover, the current density is
as high as 580 μA μm<sup>–1</sup> at a low electric
field of 10 kV cm<sup>–1</sup>. Our studies demonstrate that
thin-film BP outperforms silicon in terms of saturation velocity and
critical field, revealing its great potential in radio-frequency electronics,
high-speed mid-infrared photodetectors, and optical modulators
Black Phosphorus Mid-Infrared Photodetectors with High Gain
Recently, black phosphorus (BP) has
joined the two-dimensional material family as a promising candidate
for photonic applications due to its moderate bandgap, high carrier
mobility, and compatibility with a diverse range of substrates. Photodetectors
are probably the most explored BP photonic devices, however, their
unique potential compared with other layered materials in the mid-infrared
wavelength range has not been revealed. Here, we demonstrate BP mid-infrared
detectors at 3.39 μm with high internal gain, resulting in an
external responsivity of 82 A/W. Noise measurements show that such
BP photodetectors are capable of sensing mid-infrared light in the
picowatt range. Moreover, the high photoresponse remains effective
at kilohertz modulation frequencies, because of the fast carrier dynamics
arising from BP’s moderate bandgap. The high photoresponse
at mid-infrared wavelengths and the large dynamic bandwidth, together
with its unique polarization dependent response induced by low crystalline
symmetry, can be coalesced to promise photonic applications such as
chip-scale mid-infrared sensing and imaging at low light levels