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.

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.

A polarization-sensitive,self-powered,broadband and fast Ti_(3)C_(2)T_(x)MXene photodetector from visible to near-infrared driven by photogalvanic effects

Broadband,self-power,and polarization-sensitivity are desirable qualities for a photodetector.However,currently few photodetectors can fulfill these requirements simultaneously.Here,we propose a Ti_(3)C_(2)T_(x)(MXene)photodetector that is driven by the photogalvanic effect with impressive performances.A polarization-sensitive photocurrent is generated at zero bias under the illumination of linearly polarized laser light of 1064 nm,with an extinction ratio of 1.11.Meanwhile,a fast response with a 32/28 ms rise/decay time and a large on/off switching ratio of 120 are achieved.Besides,a robust zero-bias photocurrent is also generated in the photodetector under the illumination of 940 and 620 nm light,as well as the white light,showing a broadband photoresponse from the near-infrared to visible.Moreover,quantum transport simulations indicate that the photogalvanic effect plays an important role in the generation of the polarized photocurrent at zero bias due to the broken space inversion symmetry of the stacked few-layer Ti_(3)C_(2)T_(x).Our results shed light on a potential application of the Ti_(3)C_(2)T_(x)–MXene in the low-power photodetection with high performances.