Search

Site- and polarity-controlled core–shell InGaN/GaN nanorod LED structures were grown by metal organic vapor phase epitaxy on Si(111). Scanning transmission electron microscope images reveal uniform multiple quantum wells on polarization-free sidewalls. Spatially resolved photoluminescence mapping on a single nanorod demonstrates that the emission at 3.0 eV stems from the polarization-free m-plane, which is supported by a fast recombination lifetime of ∼490 ps at low temperatures. Quasi-resonant laser excitation demonstrates predominant radiative recombination at low excitation densities, whereas at high excitation densities, the efficiency is lowered by Auger recombination and/or carrier leakage. [ABSTRACT FROM AUTHOR]

Scanning electron microscope (SEM) induced nanowire (NW) attraction or bundling is a well known effect, which is mainly ascribed to structural or material dependent properties. However, there have also been recent reports of electron beam induced nanowire bending by SEM imaging, which is not fully explained by the current models, especially when considering the electrodynamic interaction between NWs. In this article, we contribute to the understanding of this phenomenon, by introducing an electro-dynamic model based on capacitor and Lorentz force interaction, where the active NW bending is stimulated by an electromagnetic force between individual wires. The model includes geometrical, electrical, and mechanical NW parameters, as well as the influence of the electron beam source parameters and is validated using in-situ observations of electron beam induced GaAs nanowire (NW) bending by SEM imaging. [ABSTRACT FROM AUTHOR]

We report on detailed structural and morphological characterizations of InAs nanowires of <001>, <111>, and <112> crystallographic directions grown on (001)B InAs wafer substrates using high-resolution transmission electron microscopy. We find that <001>-oriented InAs nanowires are cubic zincblende-type structure and free of planar defects. The <111>- and <112>-oriented InAs nanowires both have densely twinned (111) planar defects that are perpendicular and parallel to the growth direction, respectively. The cross sections of all three types of InAs nanowires are obtained from 3D reconstructions using electron tomography. The characteristics of the planar defects and the 3D wire shape should provide better estimations of microstructure-relevant physical properties, such as conductivity and Young's modulus of InAs nanowires. [ABSTRACT FROM AUTHOR]

We report on controlled p-type doping of GaAs nanowires grown by metal-organic vapor-phase epitaxy on (111)B GaAs substrates using the vapor-liquid-solid growth mode. p-type doping of GaAs nanowires was realized by an additional diethyl zinc flow during the growth. Compared to nominally undoped structures, the current increases by more than six orders of magnitude. The transfer characteristics of fabricated nanowire metal-insulator-semiconductor field-effect transistor devices proved p-type conductivity. By adjusting the II/III ratio, controlled doping concentrations from 4.6×1018 up to 2.3×1019 cm-3 could be achieved at a growth temperature of 400 °C. The doping concentrations were estimated from electrical conductivity measurements applied to single nanowires with different diameters. This estimation is based on a mobility versus carrier concentration model with surface depletion included. [ABSTRACT FROM AUTHOR]

GaAs nanowhiskers were grown by metal-organic vapor-phase epitaxy on (111)B GaAs substrates. The diameter of the nanowhiskers was defined by monodisperse Fe nanoparticles deposited on the GaAs substrate from the vapor phase. The growth temperature of the whiskers was investigated from 480 to 520 °C. The whiskers are preferentially directed along the crystal orientations of <001>, <111>, and their equivalents. High-resolution transmission electron microscopy characterization including energy disperse x-ray spectroscopy measurements revealed not only iron oxide but also arsenic inside the seed particle at the top of the GaAs whiskers. This indicates that the particle stays at the top during the whisker growth. [ABSTRACT FROM AUTHOR]

Resistance profiles along as-grown GaAs nanowires were measured with a multi-tip scanning tunneling microscope used as a nanoprober. The nanowires were grown in the vapor-liquid-solid growth mode in a two-temperature-step mode and doped with Zn. Using a transport model, the resistance profile was converted to a dopant profile. The dopant distribution along the nanowires was found to correlate with the temperature during different phases of nanowire growth. The nanowire base grown at higher temperature exhibits a decreased dopant concentration. Mechanical stress by intentional bending of a nanowire was shown not to influence nanowire conductance. [ABSTRACT FROM AUTHOR]