The high speed on-off performance of GaN-based light-emitting diodes (LEDs) grown in c-plane direction is limited by long carrier lifetimes caused by spontaneous and piezoelectric polarization. This work demonstrates that this limitation can be overcome by m-planar core-shell InGaN/GaN nanowire LEDs grown on Si(111). Time-resolved electroluminescence studies exhibit 90-10% rise- and fall-times of about 220 ps under GHz electrical excitation. The data underline the potential of these devices for optical data communication in polymer fibers and free space.

We have investigated the deterioration of field effect transistors based on twodimensional materials due to irradiation with swift heavy ions. Devices were prepared with exfoliated single layers of MoS 2 and graphene, respectively. They were characterized before and after irradiation with 1.14 GeV U 28+ ions using three different fluences. By electrical characterization, atomic force microscopy and Raman spectroscopy we show that the irradiation leads to significant changes of structural and electrical properties. At the highest fluence of 4 × 10 11 ions/cm 2 , the MoS 2 transistor is destroyed, while the graphene based device remains operational, albeit with an inferior performance. * electronic address: marika.schleberger@uni-due.de

Heterostructure n-GaAs/InGaP/p-GaAs core-multishell nanowire diodes are synthesized by metal-organic vapor-phase epitaxy. This structure allows a reproducible, selective wet etching of the individual shells and therefore a simplified contacting of single nanowire p-i-n junctions. Nanowire diodes show leakage currents in a low pA range and at a high rectification ratio of 3500 (at ±1V). Pronounced electroluminescence at 1.4 eV is measured at room temperature and gives evidence of the device quality. Photocurrent generation is demonstrated at the complete area of the nanowire p-i-n junction by scanning photocurrent microscopy. A solar-conversion efficiency of 4.7%, an open-circuit voltage of 0.5 V and a fill factor of 52% are obtained under AM 1.5G conditions. These results will guide the development of nanowire-based photonic and photovoltaic devices.

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