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

MoS2 Nanoribbon Transistors: Transition from Depletion-mode to Enhancement-mode by Channel Width Trimming

We study the channel width scaling of back-gated MoS2 metal-oxide-semiconductor field-effect transistors (MOSFETs) from 2 {\mu}m down to 60 nm. We reveal that the channel conductance scales linearly with channel width, indicating no evident edge damage for MoS2 nanoribbons with widths down to 60 nm as defined by plasma dry etching. However, these transistors show a strong positive threshold voltage (VT) shift with narrow channel widths of less than 200 nm. Our results also show that transistors with thinner channel thicknesses have larger VT shifts associated with width scaling. Devices fabricated on a 6 nm thick MoS2 crystal underwent the transition from depletion-mode to enhancement-mode.Comment: 3 pages, 3 figures, to appear in IEEE Electron Device Letter

Magneto-Transport in MoS2: Phase Coherence, Spin Orbit Scattering and the Hall Factor

We have characterized phase coherence length, spin orbit scattering length, and the Hall factor in n-type MoS2 2D crystals via weak localization measurements and Hall-effect measurements. Weak localization measurements reveal a phase coherence length of ~50 nm at T = 400 mK for a few-layer MoS2 film, decreasing as T^-1/2 with increased temperatures. Weak localization measurements also allow us, for the first time without optical techniques, to estimate the spin orbit scattering length to be 430 nm, pointing to the potential of MoS2 for spintronics applications. Via Hall-effect measurements, we observe a low temperature Hall mobility of 311 cm2/Vs at T = 1 K which decreases as a power law with a characteristic exponent {\gamma}=1.5 from 10 K to 60 K. At room temperature, we observe Hall mobility of 24 cm2/Vs. By determining the Hall factor for MoS2 to be 1.35 at T = 1 K and 2.4 at room temperature, we observe drift mobility of 420 cm2/Vs and 56 cm2/Vs at T = 1 K and room temperature, respectively.Comment: ACS Nano nn402377

High-performance field effect transistors with self-assembled nanodielectrics

Field effect transistor devices comprising III-V semiconductors and organic gate dielectric materials, such dielectric materials as can afford flexibility in device design and fabrication