Van der Waals Contact to 2D Semiconductors with a Switchable Electric Dipole: Achieving Both n‐ and p‐Type Ohmic Contacts to Metals with a Wide Range of Work Functions

AbstractMetal contacts to two-dimensional (2D) semiconductors are often plagued by the strong Fermi level pinning (FLP) effect which reduces the tunability of the Schottky barrier height (SBH) and degrades the performance of 2D semiconductor devices. Here, we show that MoSi2N4 and WSi2N4 monolayers—an emerging 2D semiconductor family with exceptional physical properties—exhibit strongly suppressed FLP and wide-range tunable SBH. An exceptionally large SBH slope parameter of S ≈ 0.7 is obtained which outperforms the vast majority of other 2D semiconductors. Such intriguing behavior arises from the septuple-layered morphology of MoSi2N4 and WSi2N4 monolayers in which the semiconducting electronic states are protected by the outlying Si–N sublayer. We identify Ti, Sc, and Ni as highly efficient Ohmic contacts to MoSi2N4 and WSi2N4 with zero interface tunneling barrier. Our findings reveal the potential of MoSi2N4 and WSi2N4 as a practical platform for designing high-performance and energy-efficient 2D semiconductor electronic devices.

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Ohmic Contacts to 2D Semiconductors through van der Waals Bonding

Advanced Electronic Materials ◽

10.1002/aelm.201500405 ◽

2016 ◽

Vol 2 (4) ◽

pp. 1500405 ◽

Cited By ~ 47

Author(s):

Mojtaba Farmanbar ◽

Geert Brocks

Keyword(s):

Ohmic Contacts ◽

Van Der Waals ◽

2D Semiconductors

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Efficient Prediction of Structural and Electronic Properties of Hybrid 2D Materials Using DFT and Machine Learning

10.26434/chemrxiv.6254756.v1 ◽

2018 ◽

Author(s):

Sherif Tawfik ◽

Olexandr Isayev ◽

Catherine Stampfl ◽

Joseph Shapter ◽

David Winkler ◽

...

Keyword(s):

Machine Learning ◽

Band Gap ◽

Density Functional ◽

2D Materials ◽

Van Der Waals ◽

Building Blocks ◽

Machine Learning Techniques ◽

Interlayer Distance ◽

Computational Screening ◽

Wide Range

Materials constructed from different van der Waals two-dimensional (2D) heterostructures offer a wide range of benefits, but these systems have been little studied because of their experimental and computational complextiy, and because of the very large number of possible combinations of 2D building blocks. The simulation of the interface between two different 2D materials is computationally challenging due to the lattice mismatch problem, which sometimes necessitates the creation of very large simulation cells for performing density-functional theory (DFT) calculations. Here we use a combination of DFT, linear regression and machine learning techniques in order to rapidly determine the interlayer distance between two different 2D heterostructures that are stacked in a bilayer heterostructure, as well as the band gap of the bilayer. Our work provides an excellent proof of concept by quickly and accurately predicting a structural property (the interlayer distance) and an electronic property (the band gap) for a large number of hybrid 2D materials. This work paves the way for rapid computational screening of the vast parameter space of van der Waals heterostructures to identify new hybrid materials with useful and interesting properties.

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Thermodynamics and Microstructure Development in the Thin Film Reaction of Aluminum on Silicon Carbide

MRS Proceedings ◽

10.1557/proc-403-489 ◽

1995 ◽

Vol 403 ◽

Cited By ~ 1

Author(s):

T. S. Hayes ◽

F. T. Ray ◽

K. P. Trumble ◽

E. P. Kvam

Keyword(s):

Thin Film ◽

Thin Films ◽

Silicon Carbide ◽

Ohmic Contacts ◽

Microstructure Development ◽

P Type ◽

Microstructural Studies

AbstractA refined thernodynamic analysis of the reaction between molen Al and SiC is presented. The calculations indicate much higher Si concentrations for saturation with respect to AkC 3 formation than previously reported. Preliminary microstructural studies confirm the formation of interfacial A14C3 for pure Al thin films on SiC reacted at 9000C. The implications of the calculations and experimental observations for the production of ohmic contacts to p-type SiC are discussed.

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Correlation between the electrical properties and the interfacial microstructures of TiAl-based ohmic contacts to p-type 4H-SiC

Journal of Electronic Materials ◽

10.1007/s11664-004-0203-x ◽

2004 ◽

Vol 33 (5) ◽

pp. 460-466 ◽

Cited By ~ 50

Author(s):

S. Tsukimoto ◽

K. Nitta ◽

T. Sakai ◽

M. Moriyama ◽

Masanori Murakami

Keyword(s):

Electrical Properties ◽

Ohmic Contacts ◽

P Type

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Improvement of the Specific Contact Resistance on P-Type 4H-SiC by Using a Highly P-Typed Doped 4H-SiC Layer Selectively Grown by VLS Transport

Materials Science Forum ◽

10.4028/www.scientific.net/msf.806.57 ◽

2014 ◽

Vol 806 ◽

pp. 57-60

Author(s):

Nicolas Thierry-Jebali ◽

Arthur Vo-Ha ◽

Davy Carole ◽

Mihai Lazar ◽

Gabriel Ferro ◽

...

Keyword(s):

Contact Resistance ◽

Ohmic Contacts ◽

Schottky Barrier Height ◽

Annealing Temperature ◽

Process Condition ◽

Specific Contact Resistance ◽

High Doping Level ◽

Annealing Temperatures ◽

Specific Contact ◽

P Type

This work reports on the improvement of ohmic contacts made on heavily p-type doped 4H-SiC epitaxial layer selectively grown by Vapor-Liquid-Solid (VLS) transport. Even before any annealing process, the contact is ohmic. This behavior can be explained by the high doping level of the VLS layer (Al concentration > 1020 cm-3) as characterized by SIMS profiling. Upon variation of annealing temperatures, a minimum value of the Specific Contact Resistance (SCR) down to 1.3x10-6 Ω.cm2 has been obtained for both 500 °C and 800 °C annealing temperature. However, a large variation of the SCR was observed for a same process condition. This variation is mainly attributed to a variation of the Schottky Barrier Height.

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First-Principles Study of a MoS2-PbS van der Waals Heterostructure Inspired by Naturally Occurring Merelaniite

Materials ◽

10.3390/ma14071649 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1649

Author(s):

Gemechis D. Degaga ◽

Sumandeep Kaur ◽

Ravindra Pandey ◽

John A. Jaszczak

Keyword(s):

Density Functional ◽

Van Der Waals ◽

Hole Mobility ◽

Functional Theory ◽

Mos2 Monolayer ◽

Naturally Occurring ◽

Weak Interlayer ◽

Bulk Structure ◽

P Type ◽

Interlayer Bonding

Vertically stacked, layered van der Waals (vdW) heterostructures offer the possibility to design materials, within a range of chemistries and structures, to possess tailored properties. Inspired by the naturally occurring mineral merelaniite, this paper studies a vdW heterostructure composed of a MoS2 monolayer and a PbS bilayer, using density functional theory. A commensurate 2D heterostructure film and the corresponding 3D periodic bulk structure are compared. The results find such a heterostructure to be stable and possess p-type semiconducting characteristics. Due to the heterostructure’s weak interlayer bonding, its carrier mobility is essentially governed by the constituent layers; the hole mobility is governed by the PbS bilayer, whereas the electron mobility is governed by the MoS2 monolayer. Furthermore, we estimate the hole mobility to be relatively high (~106 cm2V−1s−1), which can be useful for ultra-fast devices at the nanoscale.

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Flexo-photoelectronic effect in n-type/p-type two-dimensional semiconductors and a deriving light-stimulated artificial synapse

Materials Horizons ◽

10.1039/d1mh00024a ◽

2021 ◽

Author(s):

Xiang Wang ◽

Xin Zhou ◽

Anyang Cui ◽

Menghan Deng ◽

Xionghu Xu ◽

...

Keyword(s):

Two Dimensional ◽

2D Semiconductors ◽

Artificial Synapse ◽

P Type

We demonstrate flexo-photoelectronic effects of both n-type and p-type 2D semiconductors.

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Selective Area Deposition of Passivants, Insulators, and Epitaxial Films of II-VI Compound Semiconductors

MRS Proceedings ◽

10.1557/proc-161-159 ◽

1989 ◽

Vol 161 ◽

Author(s):

D.L. Dreifus ◽

Y. Lansari ◽

J.W. Han ◽

S. Hwang ◽

J.W. Cook ◽

...

Keyword(s):

Ohmic Contacts ◽

Epitaxial Films ◽

Semiconductor Surface ◽

Epitaxial Layers ◽

Double Crystal ◽

Surface Areas ◽

Selective Area ◽

Lift Off ◽

P Type ◽

Area Deposition

ABSTRACTII-VI semiconductor surface passivants, insulators, and epitaxial films have been deposited onto selective surface areas by employing a new masking and lift-off technique. The II-VI layers were grown by either conventional or photoassisted molecular beam epitaxy (MBE). CdTe has been selectively deposited onto HgCdTe epitaxial layers as a surface passivant. Selective-area deposition of ZnS has been used in metal-insulator-semiconductor (MIS) structures. Low resistance ohmic contacts to p-type CdTe:As have also been realized through the use of selectively-placed thin films of the semi-metal HgTe followed by a thermal evaporation of In. Epitaxial layers of HgTe, HgCdTe, and HgTe-CdTe superlattices have also been grown in selective areas on CdZnTe substrates, exhibiting specular morphologies and double-crystal x-ray diffraction rocking curves (DCXD) with full widths at half maximum (FWHMs) as narrow as 140 arcseconds.

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