Diameter-Dependent Electron Mobility of InAs Nanowires (original) (raw)
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Observation of Space-Charge-Limited Transport in InAs Nanowires
IEEE Transactions on Nanotechnology, 2000
Recent theory and experiment have suggested that space-charge-limited transport should be prevalent in high aspect-ratio semiconducting nanowires. We report on InAs nanowires exhibiting this mode of transport and utilize the underlying theory to determine the mobility and effective carrier concentration of individual nanowires, both of which are found to be diameter-dependent. Intentionally induced failure by Joule heating supports the notion of space-charge limited transport and proposes reduced thermal conductivity due to the nanowires' polymorphism.
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.
Effect of Si-doping on InAs nanowire transport and morphology
Journal of Applied Physics, 2011
The effect of Si-doping on the morphology, structure, and transport properties of nanowires was investigated. The nanowires were deposited by selective-area metal organic vapor phase epitaxy in an N 2 ambient. It is observed that doping systematically affects the nanowire morphology but not the structure of the nanowires. However, the transport properties of the wires are greatly affected. Room-temperature four-terminal measurements show that with an increasing dopant supply the conductivity monotonously increases. For the highest doping level the conductivity is higher by a factor of 25 compared to only intrinsically doped reference nanowires. By means of back-gate field-effect transistor measurements it was confirmed that the doping results in an increased carrier concentration. Temperature dependent resistance measurements reveal, for lower doping concentrations, a thermally activated semiconductor-type increase of the conductivity. In contrast, the nanowires with the highest doping concentration show a metal-type decrease of the resistivity with decreasing temperature. V
ACS Nano, 2011
We report a novel method for probing the gate-voltage dependence of the surface potential of individual semiconductor nanowires. The statistics of electronic occupation of a single defect on the surface of the nanowire, determined from a random telegraph signal, is used as a measure for the local potential. The method is demonstrated for the case of one or two switching defects in indium arsenide (InAs) nanowire field effect transistors at temperatures T = 25-77 K. Comparison with a self-consistent model shows that surface potential variation is retarded in the conducting regime due to screening by surface states with density D ss ≈ 10 12 cm-2 eV-1. Temperature-dependent dynamics of electron capture and emission producing the random telegraph signals are also analyzed, and multiphonon emission is identified as the process responsible for capture and emission of electrons from the surface traps. Two defects studied in detail had capture activation energies of E B ≈ 50 meV and E B ≈ 110 meV and cross sections of σ ¥ ≈ 3 Â 10-19 cm 2 and σ ¥ ≈ 2 Â 10-17 cm 2 , respectively. A lattice relaxation energy of Spω = 187 (15 meV was found for the first defect.
Transport characterization in nanowires using an electrical nanoprobe
Semiconductor Science and Technology, 2010
Electrical transport in semiconductor nanowires is commonly measured in a field effect transistor configuration, with lithographically defined source, drain and in some cases, top gate electrodes. This approach is labor intensive, requires high-end fabrication equipment, exposes the nanowires to extensive processing chemistry and places practical limitations on minimum nanowire length. Here we describe an alternative, simple method for characterizing electrical transport in nanowires directly on the growth substrate, without any need for post growth processing. Our technique is based on contacting nanowires using a nano-manipulator probe retrofitted inside of a scanning electron microscope. Using this approach, we characterize electrical transport in GaN nanowires grown by catalyst-free selective epitaxy, as well as InAs and Ge nanowires grown by a Au-catalyzed vapor solid liquid technique. We find that in situations where contacts are not limiting carrier injection (GaN and InAs nanowires), electrical transport transitions from Ohmic conduction at low bias to space-charge-limited conduction at higher bias. Using this transition and a theory of space-charge-limited transport which accounts for the high aspect ratio nanowires, we extract the mobility and the free carrier concentration. For Ge nanowires, we find that the Au catalyst forms a Schottky contact resulting in rectifying current-voltage characteristics, which are strongly dependent on the nanowire diameter. This dependence arises due to an increase in depletion width at decreased nanowire diameter and carrier recombination at the nanowire surface.
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.
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.
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.