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Silicon clusters embedded in a silicon dioxide matrix were prepared by ultrasound-assisted implantation resulting in a modified concentration of suboxide states as revealed by high-resolution photoelectron spectroscopy. It is suggested that ultrasound treatment results in formation of different interface structure between silicon cluster and silicon dioxide(More)
Cathodoluminescence spectra recorded with high spatial and wavelength resolution on tilted ZnO epitaxial layers allow to identify a very prominent emission peak at 3.314 eV as a free electron to shallow acceptor (E A % 130 meV) transition. By correlation with TEM cross-section images recorded on the same samples we can find these acceptor states to be(More)
We report the growth of high crystal quality Al0.3Ga0.7N directly on sapphire substrates with metalorganic vapour phase epitaxy. We studied the improvements in crystal quality by introducing an in-situ deposited SiNx interlayer. It acts as a nanomask which results in termination of the dislocations near the interface between the nanomask and epilayer. The(More)
Using mixtures of repulsive superparamagnetic polystyrene particles and a photopolymerizable organic liquid (trimethylolpropane trimethacrylate) that are applied to a water surface, it is possible to prepare porous membranes with controlled porosity. The particles were polarized by applying a magnetic field H perpendicular to the interface and spread out(More)
We study the lasing dynamics of individual ZnO nanorods by time-resolved mu-photoluminescence. The distinct laser modes show gain competition and pronounced shifts as a function of excitation density. This behavior can be understood in terms of many-particle effects within an inverted electron-hole plasma and of the calculated mode spectra of the particular(More)
A semipolar GaInN based light-emitting diode (LED) sample is investigated by three-dimensionally resolved cathodoluminescence (CL) mapping. Similar to conventional depth-resolved CL spectros-copy (DRCLS), the spatial resolution perpendicular to the sample surface is obtained by calibration of the CL data with Monte-Carlo-simulations (MCSs) of the primary(More)
This article reviews the piezoelectric properties of III-nitrides with emphasis on GaN, InN, and their ternary alloys. After a short literature survey we concentrate on semipolar and nonpolar quantum wells grown on crystal planes other than the commonly used c plane ({0001}). The electrostatic field within a quantum well causes a quantum confined Stark(More)
Group III nitrides are promising materials for light emitting diodes (LEDs). The occurrence of structural defects strongly affects the efficiency of these LEDs. We investigate the optical properties of basal plane stacking faults (BFSs), and the assignment of specific spectral features to distinct defect types by direct correlation of localized emission(More)