MoS2 Dual-Gate MOSFET with Atomic-Layer-Deposited Al2O3 as Top-Gate Dielectric

We demonstrate atomic-layer-deposited (ALD) high-k dielectric integration on two-dimensional (2D) layer-structured molybdenum disulfide (MoS2) crystals and MoS2 dual-gate n-channel MOSFETs with ALD Al2O3 as top-gate dielectric. Our C-V study of MOSFET structures shows good interface between 2D MoS2 crystal and ALD Al2O3. Maximum drain currents using back-gates and top-gates are measured to be 7.07mA/mm and 6.42mA/mm at Vds=2V with a channel width of 3 {\mu}m, a channel length of 9 {\mu}m, and a top-gate length of 3 {\mu}m. We achieve the highest field-effect mobility of electrons using back-gate control to be 517 cm^2/Vs. The highest current on/off ratio is over 10^8.Comment: submitted to IEEE Electron Device Letter

Atomic-Layer-Deposited Al2O3 on Bi2Te3 for Topological Insulator Field-Effect Transistors

We report dual-gate modulation of topological insulator field-effect transistors (TI FETs) made on Bi2Te3 thin flakes with integration of atomic-layer-deposited (ALD) Al2O3 high-k dielectric. Atomic force microscopy study shows that ALD Al2O3 is uniformly grown on this layer-structured channel material. Electrical characterization reveals that the right selection of ALD precursors and the related surface chemistry play a critical role in device performance of Bi2Te3 based TI FETs. We realize both top-gate and bottom-gate control on these devices, and the highest modulation rate of 76.1% is achieved by using simultaneous dual gate control.Comment: 4 pages, 3 figure

Electron spin magnetism of zigzag graphene nanoribbon edge states

The electron spin states of zigzag graphene nanoribbon (ZGNR) edge play a pivotal role in the applications of graphene nanoribbons. However, the exact arrangements of the electron spins remain unclear to date. In this report, the electronic spin states of the ZGNR edge have been elucidated through a combination of quantum chemical investigation and previous electron spin resonance experiment observations. An alternating alpha and beta spin configuration of the unpaired electrons along the ZGNR edge is established in ambient condition without any external magnetic field, and the origin of the spin magnetism of the ZGNR edge is revealed. It paves a pathway for the understanding and design of graphene based electronic and spintronic devices. (C) 2014 AIP Publishing LLC

GaSb Inversion-Mode PMOSFETs With Atomic-Layer-Deposited Al2O3 as Gate Dielectric

GaSb inversion-mode PMOSFETs with atomic-layer-deposited (ALD) Al2O3 as gate dielectric are demonstrated. A 0.75-mu m-gate-length device has a maximum drain current of 70 mA/mm, a transconductance of 26 mS/mm, and a hole inversion mobility of 200 cm(2)/V . s. The OFF-state performance is improved by reducing the ALD growth temperature from 300 degrees C to 200 degrees C. The measured interface trap distribution shows a low interface trap density of 2 x 10(12) /cm(2) . eV near the valence band edge. However, it increases to 1 - 4 x 10(13) /cm(2) . eV near the conduction band edge, leading to a drain current on-off ratio of 265 and a subthreshold swing of similar to 600 mV/decade. GaSb, similar to Ge, is a promising channel material for PMOSFETs due to its high bulk hole mobility, high density of states at the valence band edge, and, most importantly, its unique interface trap distribution and trap neutral level alignment

First Experimental Demonstration of Gate-all-around III-V MOSFET by Top-down Approach

The first inversion-mode gate-all-around (GAA) III-V MOSFETs are experimentally demonstrated with a high mobility In0.53Ga0.47As channel and atomic-layer-deposited (ALD) Al2O3/WN gate stacks by a top-down approach. A well-controlled InGaAs nanowire release process and a novel ALD high-k/metal gate process has been developed to enable the fabrication of III-V GAA MOSFETs. Well-behaved on-state and off-state performance has been achieved with channel length (Lch) down to 50nm. A detailed scaling metrics study (S.S., DIBL, VT) with Lch of 50nm - 110nm and fin width (WFin) of 30nm - 50nm are carried out, showing the immunity to short channel effects with the advanced 3D structure. The GAA structure has provided a viable path towards ultimate scaling of III-V MOSFETs.Comment: IEEE IEDM 2011 pp. 769-772; Structures are valuable for low-dimensional physics stud