Martin Eickhoff

University of Bremen

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M. Stutzmann

Schott (Germany)

Jörg Schörmann

University of Giessen

Pascal Hille

University of Bremen

J. Teubert

University of Giessen

O. Ambacher

University of Freiburg

Florian Furtmayr

Schott (Germany)

E. Monroy

CEA Grenoble

G. Krötz

Kempten University of Applied Sciences

Andreas Rosenauer

University of Bremen

Gerhard Müller

Munich University of Applied Sciences

Cooperative Institutions

University of Giessen

Centre National de la Recherche Scientifique

University of Bremen

Technical University of Munich

Schott (Germany)

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

CEA Grenoble

Technische Universität Berlin

Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)

Technische Universität Ilmenau

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Electronics and sensors based on pyroelectric AlGaN/GaN heterostructures – Part B: Sensor applications

Physica status solidi. C, Conferences and critical reviews/Physica status solidi. C, Current topics in solid state physics (2003)

Martin Eickhoff J. Schalwig Gustav Steinhoff O. Weidemann L. Görgens

In the present article recent results concerning sensor applications of AlGaN layers and AlGaN/GaN heterostructures are summarized. The piezoresistive effect in piezoelectric AlGaN layers is investigated and the dependence of the piezoresistive gauge factor on the Al content is attributed to the influence of strain induced piezoelectric fields. An enhancement of this effect is observed in AlGaN/GaN heterostructures resulting in high longitudinal gauge factors. The response of gas sensitive Pt:GaN Schottky diodes to hydrogen and hydrogen containing gases is analyzed up to temperatures of 600 °C and employed to realize gas sensitive field effect transistors which are demonstrated to operate up to 400 °C. In addition, ion sensitive field effect transistors (ISFETs) have also been fabricated on the basis of AlGaN/GaN heterostructures. The GaN surface shows a high pH sensitivity which is attributed to the presence of a thin native metal oxide layer on the surface. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Piezoresistive effect

Gauge factor

10.1002/pssc.200303139

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Citations (134)

Electroreflectance and Photoreflectance Studies of Electric Fields in Pt/GaN Schottky Diodes and AlGaN/GaN Heterostructures

MRS Proceedings (2002)

S. Shokhovets R. Goldhahn G. Gobsch O. Ambacher I. P. Smorchkova

Wide-bandgap semiconductor

10.1557/proc-743-l3.57

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TEM-based electron energy-loss spectroscopy of (In,Ga)N/GaN heterostructure nanowires: influence of strain and composition

Acta Crystallographica Section A Foundations of Crystallography (2010)

Holm Kirmse Ines Häusler Wolfgang Neumann Ph. Komninou Th. Kehagias

Page s169 s169phase-specific domain wall configurations [1], and hence, reorientations occur during thermal cycling.This feature may be of practical use as the preparation of electrolyte and electrode ceramics for SOFC includes compaction during one of the synthesis stages.Ceramics of LSGM can be approximated by an ensemble of small crystallites.Mechanical pressure imposed to such an electrolyte pellet causes the rearrangement of the twin structure of "chevron cells" in ceramic grains along the direction parallel or nearly parallel to the imposed pressure.Hence, such pressure will cause memory texturing of twin "chevrons" in electrolyte layers along the direction of oxygen diffusion in the SOFC structure.Keeping in mind the influence of twin walls on the conductivity and the high density of twin walls in LSGM solid solutions, it is supposed that texturing of the twins, e.g.reorientation of "chevron cells" increases the conductivity of the perovskite-type electrolyte LSGM along the cathode-anode direction.Acknowledgments.

Strain (injury)

10.1107/s0108767310096182

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Near-UV optical-cavities n Ga_2O_3 nanowires

Manuel Alonso Orts Gerwin Chilla Rudolfo Hötzel Emilio Nogales J. San Juán

In this Letter, we report optical confinement in the near-ultraviolet (near-UV) range in Ga2O3 nanowires (NWs) by distributed Bragg reflector (DBR) nanopatterned cavities. High-contrast DBRs, which act as the end mirrors of the cavities of the desired length, are designed and fabricated by focused ion beam etching. The resonant modes of the cavities are analyzed by micro-photoluminescence measurements, analytical models, and simulations, which show very good agreement between each other. Experimental reflectivities up to 50% are obtained over the 350-410 nm region for the resonances in this wavelength range. Therefore, Ga2O3 NW optical cavities are shown as good candidates for single-material-based near-UV light emitters.

Ultraviolet

Reflector (photography)

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Opto-chemical sensor system for the detection of H2 and hydrocarbons based on InGaN/GaN nanowires

Sensors and Actuators B Chemical (2012)

Sumit Paul Andreas Helwig Gerhard Müller Florian Furtmayr J. Teubert

10.1016/j.snb.2012.06.022

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Citations (50)

Impact of silicon incorporation on the formation of structural defects in AlN

Journal of Applied Physics (2006)

Martin Hermann Florian Furtmayr Francisco M. Morales O. Ambacher M. Stutzmann

The impact of Si impurities on the structural properties of AlN, grown by plasma-assisted molecular-beam epitaxy on c-plane sapphire is studied. Under nitrogen-rich growth conditions silicon can be homogeneously incorporated up to Si concentrations of [Si]=5.2×1021 cm−3. The presence of silicon on the surface during the growth process is demonstrated to be beneficial for the surface morphology and the structural properties of the AlN films. For [Si] up to (5±3)×1020 cm−3, this surfactant behavior results in a decrease of the surface roughness from 8 nm for undoped layers grown in a nitrogen-rich regime to less than 1 nm. In addition, high resolution x-ray diffraction studies reveal an increase of the average lateral crystal size from 300 nm to more than 1 μm and a simultaneous decrease of the screw dislocation density from 3.8×108 cm−2 for (comparably) weakly doped samples to 2×107 cm−2. At the same [Si] the heterogeneous stress shows a minimum of less than 50 MPa and drastically increases for higher [Si]. The analysis of edge dislocations as a function of [Si] reveals that their density is directly related to Si-induced compressive biaxial stress which increases up to (2.0±0.15) GPa, independently determined by x-ray diffraction and Raman spectroscopy. While edge dislocations are found to be strongly correlated with the release of stress, screw dislocations are formed due to the coalescence of AlN islands with different stacking order, as their density is decreasing with increasing lateral crystal size. For AlN films with [Si]<1.2×1021 cm−3, a Poisson ratio ν=0.525±0.022 is determined.

Coalescence (physics)

10.1063/1.2363239

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Citations (20)

Piezoresistive properties of single crystalline, polycrystalline, and nanocrystalline n-type 3C-SiC

Journal of Applied Physics (2004)

Martin Eickhoff Martin Möller G. Kroetz M. Stutzmann

A detailed experimental study of the influence of crystal quality on the piezoresistive properties of n-type cubic silicon carbide grown by low temperature, low pressure chemical vapor depostion is presented. We have measured the longitudinal gauge factor in single-crystalline, polycrystalline, and nanocrystalline films as a function of conductivity and temperature as well as its directional dependence. In single-crystalline films, the piezoresistive gauge factor is strongly influenced by the layer thickness. The transition from single-crystalline to nanocrystalline 3C-SiC, achieved by a decrease in deposition temperature from 1200 to 1100°C, is shown to result in a change of the corresponding longitudinal piezoresistive gauge factor from −24.8 to positive values of +8 in nominally undoped films. In addition, we observe a drastic change in its dependence on conductivity. We attribute these results to the influence of crystal defects on the strain dependent conductivity.

Piezoresistive effect

Gauge factor

Nanocrystalline material

Nanocrystalline silicon

10.1063/1.1775052

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Citations (40)

Photoelectrochemical response of GaN, InGaN, and GaNP nanowire ensembles

Journal of Applied Physics (2018)

Jan M. Philipps Sara Hölzel Pascal Hille Jörg Schörmann Sangam Chatterjee

The photoelectrochemical responses of GaN, GaNP, and InGaN nanowire ensembles are investigated by the electrical bias dependent photoluminescence, photocurrent, and spin trapping experiments. The results are explained in the frame of the surface band bending model. The model is sufficient for InGaN nanowires, but for GaN nanowires the electrochemical etching processes in the anodic regime have to be considered additionally. These processes lead to oxygen rich surface (GaxOy) conditions as evident from energy dispersive X-ray fluorescence. For the GaNP nanowires, a bias dependence of the carrier transfer to the electrolyte is not reflected in the photoluminescence response, which is tentatively ascribed to a different origin of radiative recombination in this material as compared to (In)GaN. The corresponding consequences for the applications of the materials for water splitting or pH-sensing will be discussed.

Photocurrent

Wide-bandgap semiconductor

Photoelectrochemistry

Band bending

10.1063/1.5024334

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Citations (4)

Selective etching of AlInN/GaN heterostructures for MEMS technology

Microelectronic Engineering (2007)

E. Sillero D. López‐Romero F. Calle Martin Eickhoff J.‐F. Carlin

Wide-bandgap semiconductor

10.1016/j.mee.2007.01.150

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Citations (14)

Kapitel 13: Medizinische Erstversorgung bei terroristischen Anschlägen in Deutschland – Wie gut sind wir vorbereitet? Welche Möglichkeiten gibt es?

Verlag Barbara Budrich eBooks (2022)

Martin Eickhoff

Bibliographie: Eickhoff, Martin: Kapitel 13: Medizinische Erstversorgung bei terroristischen Anschlägen in Deutschland – Wie gut sind wir vorbereitet? Welche Möglichkeiten gibt es?, Jahrbuch Terrorismus, Band 9 (2019/2021), S. 349-374. https://doi.org/10.3224/84742401.14

10.3224/84742401.14

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