Suppressing the excess OFF-state current of short-channel InAs nanowire field-effect transistors by nanoscale partial-gate

Enhancing the electrical performance of InAs nanowire field-effect transistors by improving the surface and interface properties by coating with thermally oxidized Y2O3

Due to their excellent electrical characteristics, InAs nanowires (NWs) have great potential as conducting channels in integrated circuits. However, the surface effect and loose native oxide coverage can deteriorate the performance of InAs NW transistors. Y₂O₃, a high-k dielectric with low Gibbs free energy, has been proposed to modify the InAs NW surface. Here, we systematically investigate the effect of Y₂O₃ coating on the performance of InAs NW field-effect transistors (FETs). We first explore the influence of the thermal oxidation process of Y₂O₃ on the performance of back-gated FETs. We then observe that the coverage of Y₂O₃/HfO₂ bilayers on the NW decreases the hysteresis (the smallest value reaches 0.1 V), subthreshold swing (SS, down to 169 mV dec^-1) and on-state resistance R_on, and increases the field-effect mobility μ_FE (up to 4876.1 cm² V^-1 s^-1) and the on-off ratio, mainly owing to the passivation effect on the NW surface. Finally, paired top-gated NW FETs with a Y₂O₃/HfO₂ bilayer and a single layer of HfO₂ dielectric are fabricated and compared. The Y₂O₃/HfO₂ bilayer provides better gate control (SS_min = 113 mV dec^-1) under a smaller gate oxide capacitance, with an interface trap density as low as 1.93 × 10¹² eV^-1 cm^-2. The use of the Y₂O₃/HfO₂ stack provides an effective strategy to enhance the performance of III-V-based transistors for future applications.

Ambipolar transport in narrow bandgap semiconductor InSb nanowires

We report on a transport measurement study of top-gated field effect transistors made out of InSb nanowires grown by chemical vapor deposition. The transistors exhibit ambipolar transport characteristics revealed by three distinguished gate-voltage regions: In the middle region where the Fermi level resides within the bandgap, the electrical resistance shows an exponential dependence on temperature and gate voltage. With either more positive or negative gate voltages, the devices enter the electron and hole transport regimes, revealed by the resistance decreasing linearly with decreasing temperature. From the transport measurement data of a 1 μm-long device made from a nanowire of 50 nm in diameter, we extracted a bandgap energy of 190-220 meV. The off-state current of this device is found to be suppressed within the measurement noise at a temperature of T = 4 K. A shorter, 260 nm-long device is found to exhibit a finite off-state current and a circumference-normalized on-state hole current of 11 μA μm^-1 at V_D = 50 mV which is the highest for such a device to our knowledge. The ambipolar transport characteristics make the InSb nanowires attractive for CMOS electronics, hybrid electron-hole quantum systems and hole based spin qubits.

Electrical Characterization of Individual Cesium Lead Halide Perovskite Nanowires Using Conductive AFM

Perovskite nanostructures have attracted much attention in recent years due to their suitability for a variety of applications such as photovoltaics, light-emitting diodes (LEDs), nanometer-size lasing, and more. These uses rely on the conductive properties of these nanostructures. However, electrical characterization of individual, thin perovskite nanowires has not yet been reported. Here, conductive atomic force microscopy characterization of individual cesium lead halide nanowires is presented. Clear differences are observed in the conductivity of nanowires containing only bromide and nanowires containing a mixture of bromide and iodide. The differences are attributed to a higher density of crystalline defects, deeper trap states, and higher inherent conductivity for nanowires with mixed bromide-iodide content.

Synthesis and Applications of III-V Nanowires

Low-dimensional semiconductor materials structures, where nanowires are needle-like one-dimensional examples, have developed into one of the most intensely studied fields of science and technology. The subarea described in this review is compound semiconductor nanowires, with the materials covered limited to III-V materials (like GaAs, InAs, GaP, InP,...) and III-nitride materials (GaN, InGaN, AlGaN,...). We review the way in which several innovative synthesis methods constitute the basis for the realization of highly controlled nanowires, and we combine this perspective with one of how the different families of nanowires can contribute to applications. One reason for the very intense research in this field is motivated by what they can offer to main-stream semiconductors, by which ultrahigh performing electronic (e.g., transistors) and photonic (e.g., photovoltaics, photodetectors or LEDs) technologies can be merged with silicon and CMOS. Other important aspects, also covered in the review, deals with synthesis methods that can lead to dramatic reduction of cost of fabrication and opportunities for up-scaling to mass production methods.