References of "Lüth, Hans"
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See detailNano-light-emitting-diodes based on InGaN mesoscopic structures for energy saving optoelectronics
Mikulics, Martin; Winden, Andreas; Marso, Michel UL et al

in Applied Physics Letters (2016), 109

Vertically integrated III-nitride based nano-LEDs (light emitting diodes) were designed and fabricated for operation in the telecommunication wavelength range in the (p-GaN/InGaN/n-GaN/sapphire) material ... [more ▼]

Vertically integrated III-nitride based nano-LEDs (light emitting diodes) were designed and fabricated for operation in the telecommunication wavelength range in the (p-GaN/InGaN/n-GaN/sapphire) material system. The band edge luminescence energy of the nano-LEDs could be engineered by tuning the composition and size of the InGaN mesoscopic structures. Narrow band edge photoluminescence and electroluminescence were observed. Our mesoscopic InGaN structures (depending on diameter) feature a very low power consumption in the range between 2 nWand 30 nW. The suitability of the technological process for the long-term operation of LEDs is demonstrated by reliability measurements. The optical and electrical characterization presented show strong potential for future low energy consumption optoelectronics. [less ▲]

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See detailDirect electro-optical pumping for hybrid CdSe nanocrystal/III-nitride based nano-light-emitting diodes
Mikulics, Martin; Arango, Y.C.; Winden, Andreas et al

in Applied Physics Letters (2016), 108

We propose a device concept for a hybrid nanocrystal/III-nitride based nano-LED. Our approach is based on the direct electro-optical pumping of nanocrystals (secondary excitation) by electrically driven ... [more ▼]

We propose a device concept for a hybrid nanocrystal/III-nitride based nano-LED. Our approach is based on the direct electro-optical pumping of nanocrystals (secondary excitation) by electrically driven InGaN/GaN nano-LEDs as the primary excitation source. To this end, a universal hybrid optoelectronic platform was developed for a large range of optically active nano- and mesoscopic structures. The advantage of the approach is that the emission of the nanocrystals can be electrically induced without the need of contacting them. The proof of principal was demonstrated for the electro-optical pumping of CdSe nanocrystals. The nano-LEDs with a diameter of 100 nm exhibit a very low current of 8 nA at 5V bias which is several orders of magnitude smaller than for those conventionally used. The leakage currents in the device layout were typically in the range of 8 pA to 20 pA/cm2 at 5V bias. The photon-photon down conversion efficiency was determined to be 27%. Microphotoluminescence and microelectroluminescence characterization demonstrate the potential for future optoelectronics and highly secure “green” information technology applications. [less ▲]

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See detailNon-uniform distribution of induced strain in gate-recessed AlGaN/GaN structure evaluated by micro-PL measurements
Mikulics, Martin; Hardtdegen, Hilde; Gregušová, Dagmar et al

in Semiconductor Science & Technology (2012), 27(10), 105008-105008

Micro-photoluminescence (μ-PL) studies were performed on AlGaN/GaN heterostructure field effect transistors (HFETs) with different gate-recessing depths. It was found that μ-PL is the method of choice for ... [more ▼]

Micro-photoluminescence (μ-PL) studies were performed on AlGaN/GaN heterostructure field effect transistors (HFETs) with different gate-recessing depths. It was found that μ-PL is the method of choice for detecting dry etching damage and simultaneously recording strain and stress in the HFET GaN layer. Lateral sub-μm resolved mapping shows that the strain in the GaN layer after recessing is partially relaxed and non-uniform. [less ▲]

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See detailResidual strain in recessed AlGaN/GaN heterostructure field-effect transistors evaluated by micro photoluminescence measurements
Mikulics, Martin; Hardtdegen, Hilde; Winden, Andreas et al

in Physica Status Solidi C. Current Topics in Solid State Physics (2012), 9(3-4), 911-914

The residual strain in AlGaN/GaN heterostructure field-effect transistors (HFETs) with recessed gates and their non-recessed counterparts were investigated by micro photoluminescence measurements (μ-PL ... [more ▼]

The residual strain in AlGaN/GaN heterostructure field-effect transistors (HFETs) with recessed gates and their non-recessed counterparts were investigated by micro photoluminescence measurements (μ-PL). It is found that strain relaxation accounts for the observed sheet carrier density reduction after gate recessing. The usefulness of the method for device processing optimization is demonstrated. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. [less ▲]

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See detailQuantum transport in narrow-gap semiconductor nanocolumns
Lüth, Hans; Blömers, Christian; Richter, Thomas et al

in Physica Status Solidi C. Current Topics in Solid State Physics (2010), 7(2), 386-389

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See detailDefect Distribution along Single GaN Nanowhiskers
Cavallini, Anna; Polenta, Laura; Rossi, Marco et al

in Nano Letters (2006), 6(7), 1548-1551

In this letter we report on spectral photoconductivity (PC) on different sections of single MBE-grown GaN nanowhiskers of diameters ranging on the order of 100 nm. The photoconductivity spectra show ... [more ▼]

In this letter we report on spectral photoconductivity (PC) on different sections of single MBE-grown GaN nanowhiskers of diameters ranging on the order of 100 nm. The photoconductivity spectra show, besides the band-gap related transition, deep-levels corresponding to the yellow, green, and blue bands. A strong spatial localization of specific photocurrent peaks has been observed, indicating that the defects responsible for such transitions are distributed inhomogeneously along the column growth direction. [less ▲]

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See detailOrigin of Improved RF Performance of AlGaN/GaN MOSHFETs Compared to HFETs,
Marso, Michel UL; Heidelberger, Gero; Indlekofer, Klaus Michael et al

in IEEE Transactions on Electron Devices (2006), 53(7), 1517-1723

In this paper, the influence of a 10-nm-thick silicondioxide layer, as a passivation or as a gate insulation, on the performance of heterojunction field-effect transistors (HFETs) and ... [more ▼]

In this paper, the influence of a 10-nm-thick silicondioxide layer, as a passivation or as a gate insulation, on the performance of heterojunction field-effect transistors (HFETs) and metal–oxide–semiconductor HFETs (MOSHFETs), based on an undoped AlGaN/GaN heterostructure on a SiC substrate, was investigated. Channel-conductivity results yield a nearly 50% increase of mobility in the MOSHFET samples compared to the unpassivated HFETs. This increase of the transport properties of the MOSHFET channel is confirmed by a similar 45% increase of the cutoff frequency, from 16.5 to 24 GHz. Hall measurements, however, show a 10% decrease of the mobility in the heterostructure with a SiO2 top layer. In this paper, the superior performance of the MOSHFET transistor, in contradiction to the Hall results, is attributed to the screening of the Coulomb scattering of the charged surface defects by the gate-metallization layer. [less ▲]

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See detailGaAs photodetectors prepared by high-energy and high-dose nitrogen implantation
Mikulics, Martin; Marso, Michel UL; Mantl, Siegfried et al

in Applied Physics Letters (2006), 89

The authors report on the fabrication and characterization of photodetectors based on nitrogen-ion-implanted GaAs and the annealing dynamics in these devices. An energy of 400 keV was used to implant N ... [more ▼]

The authors report on the fabrication and characterization of photodetectors based on nitrogen-ion-implanted GaAs and the annealing dynamics in these devices. An energy of 400 keV was used to implant N ions in a GaAs substrate at an ion concentration of 1 1016 cm−2. Dark current measurements as well as measurements under illumination show that the material properties rapidly change during the annealing process. Photodetectors based on nitrogen-implanted GaAs materials with annealing temperatures up to 400 °C exhibit a subpicosecond carrier lifetime up to 0.6 ps. These properties make nitrogen-ion-implanted GaAs an ideal material for ultrafast photodetectors, as alternative to low-temperature-grown GaAs. [less ▲]

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See detailGrowth and properties of GaN and AlN layers on silver substrates
Mikulics, Martin; Kočan, Martin; Rizzi, Angela et al

in Applied Physics Letters (2005), 87

We report on the preparation and properties of GaN and AlN layers grown by molecular-beam epitaxy on silver metal substrates. X-ray diffraction rocking curves show polycrystalline character of GaN with ... [more ▼]

We report on the preparation and properties of GaN and AlN layers grown by molecular-beam epitaxy on silver metal substrates. X-ray diffraction rocking curves show polycrystalline character of GaN with high preferential GaN 11-22 orientation. An intermetallic phase of Ga3Ag is found at the GaN/Ag interface. On the other hand, AlN layers exhibit a monocrystalline structure with a growth direction of 0002 . Schottky diodes prepared on GaN layers show good rectifying behavior and relatively low leakage current 10−3 A/cm2 . These results indicate that the III-nitride growth on metallic substrates might be used for low-cost and large-area electronic and photonic devices. [less ▲]

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See detailSize-dependent Photoconductivity in MBE-Grown GaN-Nanowires
Calarco, Raffaella; Marso, Michel UL; Richter, Thomas et al

in Nano Letters (2005), 5(5), 981-984

We report on electrical transport in the dark and under ultraviolet (UV) illumination through GaN nanowhiskers grown by molecular beam epitaxy (MBE), which is sensitively dependent on the column diameter ... [more ▼]

We report on electrical transport in the dark and under ultraviolet (UV) illumination through GaN nanowhiskers grown by molecular beam epitaxy (MBE), which is sensitively dependent on the column diameter. This new effect is quantitatively described by a size dependent surface recombination mechanism. The essential ingredient for the interpretation of this effect is a diameter dependent recombination barrier, which arises from the interplay between column diameter and space charge layer extension at the column surface. [less ▲]

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