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We report on individual-InAs nanowire optoelectronic devices which, through surface-state engineering, can be tailored to exhibit either negative- or positive-photoconductivity, opening pathways towards engineering semiconductor nanowires for novel optical-memory and photodetector applications.
We report the first GaN nanowire structure incorporating a GaN/ScxGa1–xN axial heterostructure. A 20 nm ScxGa1−xN layer was inserted into GaN nanowires grown by a catalyst‐free self‐assembled method using plasma‐assisted molecular beam epitaxy (PA‐MBE). The insertion was characterised by energy dispersive X‐ray spectroscopy in the scanning transmission electron microscope (STEM‐EDX). High resolution...
Reliable doping in GaAs nanowires is essential for the development of novel optoelectronic devices. Previously, GaAs nanowires have been shown to exhibit extremely short photoconductivity lifetimes of a few picoseconds due to their high surface recombination velocity, which is detrimental for nanowire devices, such as solar cells and nanowire lasers. Here, we show that, by exploiting engineered band-bending...
In order to realize many devices based on semiconductor nanowires, reliable doping is essential. For such devices, it is important that the electron mobility is not compromised by doping incorporation. Here, we show that core-shell GaAs/AlGaAs nanowires can be modulation n-type doped with negligible loss of electron mobility. Optical pump terahertz probe spectroscopy is used as a novel, reliable,...
We have studied the electronic transport characteristics of nanowire field effect transistors (NWFETs) made from phase-pure wurtzite (WZ) and zinc blende (ZB) InAs nanowires (NWs). The electronic characteristics were obtained at temperatures between 4 and 300 K. The ZB NWFETs exhibited a greater sensitivity to the surrounding atmosphere than WZ NWFETs. The WZ NWFETs had a higher mobility than ZB NWFETs...
We report a comparative study of the electronic properties of nominally identical nanowire field-effect transistor (NW-FET) devices produced using 50 nm diameter InAs nanowires that differ only in phase: ZB on the one hand, and WZ on the other. We find much higher current densities in the ZB NW-FETs, and on/off ratios of up to 100.
We have used terahertz spectroscopy to measure the conductivity and time-resolved photoconductivity of a range of semiconducting nanostructures. This article focuses on our recent terahertz conductivity studies on semiconductor nanowires and single walled carbon nanotubes.
The sidewall facets of GaAs nanowires (NWs) were studied. It has been found that the sidewalls of GaAs NWs grown at 450 °C are {112} facets. However, the sidewalls of GaAs NWs start to become {110} during the postannealing at 650 °C for 30 min.
GaAs nanowires were grown on Si (111) substrates. By coating a thin GaAs buffer layer on Si surface and using a two-temperature growth, the morphology and crystal structure of GaAs nanowires were dramatically improved. The strained GaAs/GaP core-shell nanowires, based on the improved GaAs nanowires with a shell thickness of 25 nm, showed a significant shift in emission energy of 260 meV from the unstrained...
Growth of Au-catalyzed InP nanowires (NWs) by metalorganic chemical vapor deposition (MOCVD) has been studied in the temperature range of 400-510°C and V/III ratio of 44-700. We demonstrate that minimal tapering of InP NWs can be achieved at 400°C and V/III ratio of 350. Zinc-blende (ZB) or wurtzite (WZ) NWs is obtained depending on the growth conditions. 4K microphotoluminescence (μ-PL) studies show...
We investigate vertical and defect-free growth of GaAs nanowires on Si (111) substrates via a vapor-liquid-solid (VLS) growth mechanism with Au catalysts by metal-organic chemical vapor deposition (MOCVD). By using annealed thin GaAs buffer layers on the surface of Si substrates, most nanowires are grown on the substrates straight, following (111) direction; by using two temperature growth, the nanowires...
GaAs was radially deposited on InAs nanowires by metal–organic chemical vapor deposition and resultant nanowire heterostructures were characterized by detailed electron microscopy investigations. The GaAs shells have been grown in wurtzite structure, epitaxially on the wurtzite structured InAs nanowire cores. The fundamental reason of structural evolution in terms of material nucleation and interfacial...
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