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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]

Upcoming THz applications require compact, robust, and efficient sources with high output‐power. Among electronic devices, resonant tunneling diodes are a promising candidate for THz operation. Triple‐barrier resonant tunneling diodes provide a high degree of design and operation freedom. Zero‐bias detection and THz emission are possible with the same device due to the asymmetric structure and IV curve. However, more investigations in the layer stack design are required. An investigation is presented into the effect of collector spacer thickness and doping profile in the subcollector contact region. The aim is to simultaneously optimize the RF output‐power and cut‐off frequency in triple‐barrier structures. A series of devices with different collector spacers and two distinct doping profiles are fabricated. A trade‐off between collector spacer thickness and doping profile for either higher output power or cut‐off frequency is observed. In addition, the simulation results are presented from a nonequilibrium Green's function solver implemented in Python. Herein, a need for accurate determination of the extent of the nonequilibrium region to achieve simulation results matching the IV measurements is observed. [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]

Insertion of a thin pseudomorphic InAlAg hole barrier layer having high Al content into the spacer of an InAlAs/InGaAs HEMT increases the valence band discontinuity and decreases the excess gate leakage current. Photocurrent and DC measurements help determine the efficiency of the hole barrier while Hall and RF measurements help determine the influence of hole barrier on transport characteristics. Experimental results show that impact ionization in the InGaAs channel is responsible for the excess gate leakage current.

In GaN‐on‐Si nanowire integration schemes, where the nanowires are contacted through the substrate, the interfaces between silicon substrate, AlN buffer layer, and GaN nanowire are of high interest. Herein, analysis by scanning transmission electron microscopy (STEM) of GaN nanowires grown on Si(111) by metal–organic vapor phase epitaxy using a polarity‐ and site‐controlled growth method is presented. This method is based on prestructuring the substrate, ex situ oxidation of the surface, and in situ oxide layer desorption. First, an AlN layer is grown to prevent melt‐back etching. Samples are prepared for STEM by focused ion beam cutting. STEM measurements in three different regions reveal that the AlN buffer material is polycrystalline. The degree of polycrystallinity is found to depend on the observed region: the highest degree exists at the field area between nanowires and the lowest at the sidewall of the Si‐pillars. On the sidewall, the c→$$ \overrightarrow{c} $$‐direction of the AlN grain is tilted by 30.1° with regard to the Si{111} sidewall plane, leading to reduced lattice mismatch at this location. The growth of GaN is competing with diffusion of Ga atoms through grain boundaries. The dominant mechanism is dependent on the region, leading to site‐controlled growth of nanowires. [ABSTRACT FROM AUTHOR]