Probing the Gate−Voltage-Dependent Surface Potential of Individual InAs Nanowires Using Random Telegraph Signals (original) (raw)
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Diameter-Dependent Electron Mobility of InAs Nanowires
Nano Letters, 2009
Temperature-dependent I-V and C-V spectroscopy of single InAs nanowire fieldeffect transistors were utilized to directly shed light on the intrinsic electron transport properties as a function of nanowire radius. From C-V characterizations, the densities of thermally-activated fixed charges and trap states on the surface of untreated (i.e., without any surface functionalization) nanowires are investigated while enabling the accurate measurement of the gate oxide capacitance; therefore, leading to the direct assessment of the field-effect mobility for electrons. The field-effect mobility is found to monotonically decrease as the radius is reduced to sub-10 nm, with the low temperature transport data clearly highlighting the drastic impact of the surface roughness scattering on the mobility degradation for miniaturized nanowires. More generally, the approach presented here may serve as a versatile and powerful platform for indepth characterization of nanoscale, electronic materials.
Direct observation of single-charge-detection capability of nanowire field-effect transistors
Nature Nanotechnology, 2010
A single localized charge can quench the luminescence of a semiconductor nanowire 1 , but relatively little is known about the effect of single charges on the conductance of the nanowire. In one-dimensional nanostructures embedded in a material with a low dielectric permittivity, the Coulomb interaction and excitonic binding energy are much larger than the corresponding values when embedded in a material with the same dielectric permittivity 2,3 . The stronger Coulomb interaction is also predicted to limit the carrier mobility in nanowires 4 . Here, we experimentally isolate and study the effect of individual localized electrons on carrier transport in InAs nanowire fieldeffect transistors, and extract the equivalent charge sensitivity. In the low carrier density regime, the electrostatic potential produced by one electron can create an insulating weak link in an otherwise conducting nanowire field-effect transistor, modulating its conductance by as much as 4,200% at 31 K. The equivalent charge sensitivity, 4 3 10 25 e Hz 21/2 at 25 K and 6 3 10 25 e Hz 21/2 at 198 K, is orders of magnitude better than conventional field-effect transistors 5 and nanoelectromechanical systems 6,7 , and is just a factor of 20-30 away from the record sensitivity for state-of-the-art single-electron transistors operating below 4 K (ref. 8). This work demonstrates the feasibility of nanowire-based single-electron memories 9 and illustrates a physical process of potential relevance for high performance chemical sensors 10,11 . The charge-state-detection capability we demonstrate also makes the nanowire field-effect transistor a promising host system for impurities (which may be introduced intentionally or unintentionally) with potentially long spin lifetimes 12,13 , because such transistors offer more sensitive spin-to-charge conversion readout than schemes based on conventional field-effect transistors 13 .
Surface State Dynamics Dictating Transport in InAs Nanowires
Nano Letters, 2018
Because of their high aspect ratio, nanostructures are particularly susceptible to effects from surfaces such as slow electron trapping by surface states. However, nonequilibrium trapping dynamics have been largely overlooked when considering transport in nanoelectronic devices. In this study, we demonstrate the profound influence of dynamic trapping processes on transport in InAs nanowires through an investigation of the hysteretic and time-dependent behaviour of the transconductance. We observe large densities (∼ 10 13 cm −2) of slow surface traps and demonstrate the ability to control and permanently fix their occupation and charge through electrostatic manipulation by the gate potential followed by thermal deactivation by cryogenic cooling.
Room temperature observation of quantum confinement in single InAs nanowires
Nano letters, 2015
Quantized conductance in nanowires can be observed at low temperature in transport measurements; however, the observation of sub-bands at room temperature is challenging due to temperature broadening. So far, conduction band splitting at room temperature has not been observed in III-V nanowires mainly due to the small energetic separations between the sub-bands. We report on the measurement of conduction sub-bands at room temperature, in single InAs nanowires, using Kelvin probe force microscopy. This method does not rely on charge transport but rather on measurement of the nanowire Fermi level position as carriers are injected into a single nanowire transistor. As there is no charge transport, electron scattering is no longer an issue, allowing the observation of the sub-bands at room temperature. We measure the energy of the sub-bands in nanowires with two different diameters, and obtain excellent agreement with theoretical calculations based on an empirical tight-binding model.
Temperature and annealing effects on InAs nanowire MOSFETs
Microelectronic Engineering, 2011
We report on temperature dependence on the drive current as well as long-term effects of annealing in vertical InAs nanowire Field-Effect Transistors. Negatively charged traps in the HfO 2 gate dielectric are suggested as one major factor in explaining the effects observed in the transistor characteristics. An energy barrier may be correlated with an un-gated InAs nanowire region covered with HfO 2 and the effects of annealing may be explained by changed charging on defects in the oxide. Initial simulations confirm the general effects on the I-V characteristics by including fixed charge.
Electronic Properties and Orientation-Dependent Performance of InAs Nanowire Transistors
IEEE Transactions on Electron Devices, 2000
The electronic properties, namely, the band structures, the band gaps, and the electron effective masses of hydrogen-passivated InAs nanowires grown in 100 , 110 , and 111 crystallographic directions are studied using sp 3 d 5 s * orbital-basis tight-binding model. We then parameterize the band gaps and electron effective masses to facilitate device simulation and to study the orientation-dependent performance of n-channel InAs nanowire transistors using a top-of-the-barrier model. The 111 and 110 wire transistors have better performance metrics. The quantum-confinement effect is largest in the 100 wire, which results in a higher band gap and a heavier effective mass for relatively smaller diameter wires. The consequence is lower current, higher density of states, higher quantum capacitance, and longer delay in the 100 wire transistors. The 110 and 111 wires have a very similar quantum-confinement effect, even for the smaller diameters, which results in similar band gaps, similar effective masses, and similar performance metrics. Index Terms-InAs nanowire transistors, orientation dependent electronic properties, orientation dependent performance metrics, parametrization of effective mass and band gap.
ACS Nano, 2014
The effect of diameter variation on electrical characteristics of long-channel InAs nanowire metalÀoxideÀsemiconductor field-effect transistors is experimentally investigated. For a range of nanowire diameters, in which significant band gap changes are observed due to size quantization, the Schottky barrier heights between source/drain metal contacts and the semiconducting nanowire channel are extracted considering both thermionic emission and thermally assisted tunneling. Nanowires as small as 10 nm in diameter were used in device geometry in this context. Interestingly, while experimental and simulation data are consistent with a band gap increase for decreasing nanowire diameter, the experimentally determined Schottky barrier height is found to be around 110 meV irrespective of the nanowire diameter. These observations indicate that for nanowire devices the density of states at the direct conduction band minimum impacts the so-called branching point. Our findings are thus distinctly different from bulk-type results when metal contacts are formed on three-dimensional InAs crystals.