2D fin field-effect transistors integrated with epitaxial high-κ gate oxide
The Peng group achieved the wafer-scale synthesis of 2D semiconductor fin/high-k gate oxide heterostructure array, and fabricated the high-performance 2D FinFET, which was pubuliched on Nature entitled as "2D fin field-effect transistors integrated with epitaxial high-κ gate oxide" (Nature 2023, 616, 66). The as-fabricated 2D fin/oxide heterostructure has ultra-flat interface and ultra-thin fin thickness down to 1unit cell (1.2 nm), which was compatible to wafer-scale high-density and site-specific synthesis. The as-fabricated 2D fin field-effect transistors (FinFETs) based on Bi2O2Se/Bi2SeO5 epitaxial heterostructures exhibit high electron mobility (μ) up to 270 cm2 V-1 s-1, ultra-low off-state current (IOFF) down to ~1 pA μm-1, high on/off current ratios (ION/IOFF) up to 108, and high on-state current (ION) up to 830 μA μm-1 at 400-nm channel length, which meet the low-power specifications projected by the International Roadmap for Devices and Systems (IRDS)4. The 2D fin-oxide epitaxial heterostructures open up new avenues for the further extension of the Moore's law.
2D semiconducting Bi2O2Se with ultrahigh mobility
The Peng research group realized the controlled syntheses of high-mobility semiconducting 2D crystals--- layered bismuth oxychalcogenides (BOX, Bi2O2X: X = S, Se, Te), and are vigorously exploring their vistas in electronics and optoelectronics. (Jinxiong Wu, et al. High electron mobility and quantum oscillations in non-encapsulated ultrathin semiconducting Bi2O2Se. Nature Nanotechnology 2017, 12, 530
A native oxide high-κ gate dielectric for two-dimensional electronics
Silicon-based transistors are approaching their physical limits and thus new high-mobility semiconductors are sought to replace silicon in the microelectronics industry. Both bulk materials (such as silicon-germanium and III–V semiconductors) and low-dimensional nanomaterials (such as one-dimensional carbon nanotubes and two-dimensional transition metal dichalcogenides) have been explored, but, unlike silicon, which uses silicon dioxide (SiO2) as its gate dielectric, these materials suffer from the absence of a high-quality native oxide as a dielectric counterpart. This can lead to compatibility problems in practical devices. Here, we show that an atomically thin gate dielectric of bismuth selenite (Bi2SeO5) can be conformally formed via layer-by-layer oxidization of an underlying high-mobility two-dimensional semiconductor, Bi2O2Se. Using this native oxide dielectric, high-performance Bi2O2Se field-effect transistors can be created, as well as inverter circuits that exhibit a large voltage gain (as high as 150). The high dielectric constant (~21) of Bi2SeO5 allows its equivalent oxide thickness to be reduced to 0.9 nm while maintaining a gate leakage lower than thermal SiO2. The Bi2SeO5 can also be selectively etched away by a wet chemical method that leaves the mobility of the underlying Bi2O2Se semiconductor almost unchanged. Nature Electronics 2020, 3, 473.
Single-crystalline van der Waals layered dielectric with high dielectric constant
The Peng group and collaborators have proposed a facile synthesis of a single-crystalline high-κ (κ of roughly 16.5) van der Waals layered dielectric Bi2SeO5. The centimetre-scale single crystal of Bi2SeO5 can be efciently exfoliated to an atomically fat nanosheet as large as 250 × 200 μm2 and as thin as monolayer .In 2D Bi2O2Se encapsulated by as-prepared Bi2SeO5 nanosheets, the quantum Hall efect is observed and the carrier mobility reaches 470,000 cm2 V−1 s−1 at 1.8 K. This work expands the realm of dielectric and opens up a new possibility for lowering the gate voltage and power consumption in 2D electronics and integrated circuits. (Nature Metarials, 2023 in press.）
Momentum-matching and band-alignment van der Waals heterostructures for high-efficiency infrared photodetection
The Peng group and collaborators have proposed the Momentum-matching and band-alignment van der Waals heterostructures for high-efficiency infrared photodetection. Based on strain-free high-quality Bi2O2Se crystal synthesized by chemical vapor deposition method, the as-prepared Bi2O2Se/BP photoelectric detector exhibited record-high quantum effiency of 84 % and 76.5 % at 1.3 μm and 2 μm respectively. (Science Advances 2022, 8, eabq1781)
Integrated wafer-scale ultra-flat graphene by gradient surface energy modulation
The Peng research group and collaborators have designed a composite transfer medium with gradient surface energy modulation for graphene transfer, and the as-transferred wafer-scale damage-free ultra-flat graphene demonstrated high-carrier mobility with room-temperature quantum Hall effect and fractional quantum Hall effect. This strategy has been proven suitable for wafer-scale transfer of other 2D materials (e.g. h-BN). (Nature communications, 2022, 13, 5410)
A single-crystalline native dielectric for two-dimensional semiconductors with an equivalent oxide thickness below 0.5 nm
The Peng research group has established UV-assisted O3 intercalative oxidation for 2D Bi2O2Se to prepare single-crystalline high-k dielectric β-Bi2SeO5 . This methods is compatible to ultra-violet lithograohy to achieve wafer-scale selected-area oxidation, and the as-prepared Bi2O2Se-Bi2SeO5 was proven atomically flat and lattice matching. The high-k dielectric β-Bi2SeO5 acts a relatively low leakage current, meeting the 2021 IRDS requirements of sub-0.5-nm-EOT dielectric and low-power limit. (Nature Electronics 2022, 5, 643).
Uniform thin ice on ultraflat graphene for high-resolution cryo-EM
The Peng research group and collaborators have reported novel ultra-flat graphene grids for cyro-EM, achieveing the preparation of uniform thin ice in high-resolution cyro-EM. This paper has proven that as-prepared uniform thin ice can improve the quality and effiency of cyro-EM, which is compatible for the structural analysis of varies of small protein.
(Nature Methods 2022, online, doi.org/10.1038/s41592-022-01693-y)