Quantum transport simulation of the two-dimensional GaSb transistors

Owing to the high carrier mobility,two-dimensional(2D)gallium antimonite(GaSb)is a promising channel material for field-effect transistors(FETs)in the post-silicon era.We investigated the ballistic performance of the 2D GaSb metal-oxide-semiconductor FETs with a 10 nm-gate-length by the ab initio quantum transport simulation.Because of the wider bandgap and better gate-control ability,the performance of the 10-nm monolayer(ML)GaSb FETs is generally superior to the bilayer counterparts,including the three-to-four orders of magnitude larger on-current.Via hydrogenation,the delaytime and power consumption can be further enhanced with magnitude up to 35%and 57%,respectively,thanks to the expanded bandgap.The 10-nm ML GaSb FETs can almost meet the International Technology Roadmap for Semiconductors(ITRS)for high-performance demands in terms of the on-state current,intrinsic delay time,and power-delay product.

Insights into the adsorption of water and oxygen on the cubic CsPbBr_(3)surfaces:A first-principles study

The degradation mechanism of the all-inorganic perovskite solar cells in the ambient environment remains unclear.In this paper,water and oxygen molecule adsorptions on the all-inorganic perovskite(CsPbBr_(3))surface are studied by density-functional theory calculations.In terms of the adsorption energy,the water molecules are more susceptible than the oxygen molecules to be adsorbed on the CsPbBr_(3)surface.The water molecules can be adsorbed on both the CsBr-and PbBr-terminated surfaces,but the oxygen molecules tend to be selectively adsorbed on the CsBr-terminated surface instead of the PbBr-terminated one due to the significant adsorption energy difference.While the adsorbed water molecules only contribute deep states,the oxygen molecules introduce interfacial states inside the bandgap of the perovskite,which would significantly impact the chemical and transport properties of the perovskite.Therefore,special attention should be paid to reduce the oxygen concentration in the environment during the device fabrication process so as to improve the stability and performance of the CsPbBr_(3)-based devices.

Super high maximum on-state currents in 2D transistors

Two-dimensional(2D)materials have been recognized as a type of potential channel material to replace silicon in future field-effect transistors(FETs)by the International Technology Roadmap for Semiconductors(ITRS)and its succesor the International Roadmap for Devices and Systems(IRDS)[1−4].Substantial first principle quantum transport simulations have predicted that many 2D transistors,including those with MoS2,WSe2,phosphorene,and Bi2O2Se channels,own excellent device performance and are able to extend Moore’s law down to the sub-10 nm scale[4].

High-performance sub-10-nm monolayer black phosphorene tunneling transistors

Moore＇s law is approaching its physical limit. Tunneling field-effect transistors （TFETs） based on two-dimensional （2D） materials provide a possible scheme to extend Moore＇s law down to the sub-10-nm region owing to the electrostatic integrity and absence of dangling bonds in 2D materials. We report an ab initio quantum transport study on the device performance of monolayer （ML） black phosphorene （BP） TFETs in the sub-10-nm scale （6-10 nm）. Under the optimal schemes, the ML BP TFETs show excellent device performance along the armchair transport direction. The on-state current, delay time, and power dissipation of the optimal sub-10-nm ML BP TFETs significantly surpass the latest International Technology Roadmap for Semiconductors （ITRS） requirements for high- performance devices. The subthreshold swings are 56-100 mV/dec, which are much lower than those of their Schottky barrier and metal oxide semiconductor field-effect transistor counterparts.

Electrical contacts in monolayer blue phosphorene devices

Semiconducting monolayer （ML） blue phosphorene （BlueP） shares similar stability with ML black phosphorene （BP）, and it has recently been grown on an Au surface. Potential ML BlueP devices often require direct contact with metal to enable the injection of carriers. Using ab initio electronic structure calculations and quantum transport simulations, for the first time, we perform a systematic study of the interfacial properties of ML BlueP in contact with metals spanning a wide work function range in a field effect transistor （FET） configuration. ML BlueP has undergone metallization owing to strong interaction with five metals. There is a strong Fermi level pinning （FLP） in the ML BlueP FETs due to the metal-induced gap states （MIGS） with a pinning factor of 0.42. ML BlueP forms n-type Schottky contact with Sc, Ag, and Pt electrodes with electron Schottky barrier heights （SBHs） of 0.22, 0.22, and 0.80 eV, respectively, and p-type Schottky contact with Au and Pd electrodes with hole SBHs of 0.61 and 0.79 eV, respectively. The MIGS are eliminated by inserting graphene between ML BlueP and the metal electrode, accompanied by a transition from a strong FLP to a weak FLP. Our study not only provides insight into the ML BlueP-metal interfaces, but also helps in the design of ML BlueP devices.

Super low contact resistance in monolayer MoS_(2) transistors

Two-dimensional(2D) materials have inspired the development of beyond-silicon electronic technology owing to their atomically thin size, flat surfaces without dangling bonds,and high mechanical strength [1-3]. Contact resistance(R_(c)) is the key to realizing high-performance 2D field-effect transistors(FETs).

二维鳍式场效应晶体管

Benefiting from good electrostatics,excellent combinations with high-j oxide dielectrics,and high device densities,Si fin field-effect transistor(FinFET)arrays are the dominant structures of current complementary metal oxide semiconductor technology.However,when Si FinFETs are extremely small,their performance deteriorates significantly due to enhanced interfacial scattering arising from thickness fluctuations and dangling bonds.In fact,the Si carrier mobility degrades drastically with the thickness:l/t 6(where l is the mobility and t is the thickness of the semiconductor)[1].Two-dimensional(2D)materials,such as graphene,transition metal dichalcogenides(TMDs),black phosphorus,and Bi2O_(2)Se,have emerged as promising building blocks for nextgeneration FETs.They exhibit excellent electrostatics due to their atomic scale thicknesses and high carrier mobilities(up to 103 cm^(2) V1 s1)from their smooth surfaces without dangling bonds[2].