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Olaf Wunnicke

Publications and source records attributed to Olaf Wunnicke.

4 recordsLinked to original sources
arXiv2007

Single quantum dot nanowire LEDs

We report reproducible fabrication of InP-InAsP nanowire light emitting diodes in which electron-hole recombination is restricted to a quantum-dot-sized InAsP section. The nanowire geometry naturally self-aligns the quantum dot with the n-InP and p-InP ends of the wire, making these devices promising candidates for electrically-driven quantum optics experiments. We have investigated the operation of these nano-LEDs with a consistent series of experiments at room temperature and at 10 K, demonstrating the potential of this system for single photon applications.

cond-mat.mes-hall↗
arXiv2006

Gate capacitance of back-gated nanowire field-effect transistors

Gate capacitances of back-gated nanowire field-effect transistors (NW-FETs) are calculated by means of finite element methods and the results are compared with analytical results of the ``metallic cylinder on an infinite metal plate model''. Completely embedded and non-embedded NW-FETs are considered. It is shown that the use of the analytical expressions also for non-embedded NW-FETs gives carrier mobilities that are nearly two times too small. Furthermore, the electric field amplification of non-embedded NW-FETs and the influence of the cross-section shape of the nanowires are discussed.

cond-mat.other↗
arXiv2002

Ballistic Spin Injection and Detection in Fe/Semiconductor/Fe Junctions

We present {\it ab initio} calculations of the spin-dependent electronic transport in Fe/GaAs/Fe and Fe/ZnSe/Fe (001) junctions simulating the situation of a spin-injection experiment. We follow a ballistic Landauer-Büttiker approach for the calculation of the spin-dependent dc conductance in the linear-responce regime, in the limit of zero temperature. We show that the bulk band structure of the leads and of the semiconductor, and even more the electronic structure of a clean and abrupt interface, are responsible for a current polarisation and a magnetoresistance ratio of almost the ideal 100%, if the transport is ballistic. In particular we study the significance of the transmission resonances caused by the presence of two interfaces.

cond-mat↗