Hailin PENG Group

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 (I_OFF) down to ~1 pA μm^-1, high on/off current ratios (I_ON/I_OFF) up to 10⁸, and high on-state current (I_ON) 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.

https://www.nature.com/articles/s41586-023-05797-z

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

https://www.nature.com/articles/nnano.2017.43

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.

https://www.nature.com/articles/s41928-020-0444-6

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.）

 https://www.nature.com/articles/s41563-023-01502-7

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)

https://www.science.org/doi/10.1126/sciadv.abq1781

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)

https://www.nature.com/articles/s41467-022-33135-w

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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-Bi₂SeO_{5 .} 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). 

https://www.nature.com/articles/s41928-022-00824-9

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)

https://www.nature.com/articles/s41592-022-01693-y