A5002665522- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- ZnO doping and properties
- Gas Sensing Nanomaterials and Sensors
- Semiconductor materials and devices
- Nanowire Synthesis and Applications
- Analytical Chemistry and Sensors
- Silicon Carbide Semiconductor Technologies
- Solar Thermal and Photovoltaic Systems
- Semiconductor Quantum Structures and Devices
- Acoustic Wave Resonator Technologies
- Metal and Thin Film Mechanics
- Photovoltaic System Optimization Techniques
- Copper-based nanomaterials and applications
- Electronic and Structural Properties of Oxides
- Molecular Junctions and Nanostructures
- Advanced Photocatalysis Techniques
- Semiconductor materials and interfaces
- Advanced MEMS and NEMS Technologies
- Diamond and Carbon-based Materials Research
- Corporate Governance and Management
- Copper Interconnects and Reliability
- Perovskite Materials and Applications
- Quantum Dots Synthesis And Properties
- Advancements in Semiconductor Devices and Circuit Design
University of Bremen
2017-2025
Staats- und Universitätsbibliothek Bremen
2024-2025
Justus-Liebig-Universität Gießen
2010-2022
Giessen School of Theology
2017
Barcelona Institute for Science and Technology
2016
Massachusetts Institute of Technology
2014
Drexel University
2014
CEA Grenoble
2014
CEA LETI
2014
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2014
The macroscopic nonlinear pyroelectric polarization of wurtzite AlxGa1-xN, InxGa1-xN and AlxIn1-xN ternary compounds (large spontaneous piezoelectric coupling) dramatically affects the optical electrical properties multilayered Al(In)GaN/GaN hetero-, nanostructures devices, due to huge built-in electrostatic fields bound interface charges caused by gradients in at surfaces heterointerfaces. Models polarization-induced effects GaN-based devices so far have assumed that nitride alloys can be...
Abstract Copper‐oxide compound semiconductors provide a unique possibility to tune the optical and electronic properties from insulating metallic conduction, bandgap energies of 2.1 eV infrared at 1.40 eV, i.e., right into middle efficiency maximum for solar‐cell applications. Three distinctly different phases, Cu 2 O, 4 O 3 , CuO, this binary semiconductor can be prepared by thin‐film deposition techniques, which differ in oxidation state copper. Their material as far they are known...
The pH-sensitivity of GaN surfaces in electrolyte solutions has been determined. For this purpose, field-effect transistors and AlGaN/GaN high-electron-mobility transistor (HEMT) structures were used to measure the response nonmetallized gate regions changes H+-concentration an ambient electrolyte. We found a linear pH between pH=2 pH=12 for both as-deposited thermally oxidized surfaces. Both showed almost Nernstian behavior with sensitivities 57.3 mV/pH GaN:Si/GaN:Mg 56.0 GaN/AlGaN/GaN HEMT...
Besides silicon carbide, group-III nitrides are also suitable large-band-gap semiconductor materials for high-temperature gas sensor devices. Exposing GaN-based Schottky diodes with catalytically active platinum electrodes to hydrogen, we observed a decrease of the rectifying characteristics which attribute in barrier height. Current–voltage and elastic recoil detection measurements were used investigate H-sensing behavior such Our results indicate an interfacial effect as origin response hydrogen.
Aberration corrected scanning transmission electron microscopy (STEM) with high angle annular dark field (HAADF) imaging and the newly developed bright (ABF) are used to define a new guideline for polarity determination of semiconductor nanowires (NWs) from binary compounds in two extreme cases: (i) when dumbbell is formed atoms similar mass (GaAs) (ii) case where one extremely light (N or O: ZnO GaN/AlN). The theoretical fundaments these procedures allow us overcome main challenge...
Metastable $ϵ$-gallium oxide is expected to have very good properties for high-power electronics, combining the large band gap and high breakdown field of $\ensuremath{\beta}$-Ga${}_{2}$O${}_{3}$ with a spontaneous polarization. Unfortunately, synthesizing $ϵ$-Ga${}_{2}$O${}_{3}$ quite tricky, yet authors managed it. Introducing tin avoids formation volatile suboxides, which leadsto widened growth window in can beformed. Furthermore, mechanism that revealcould be relevant any binary oxide.
The self-assembled growth of GaN nanorods on Si (111) substrates by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions is investigated. An amorphous silicon nitride layer formed in the initial stage that prevents formation a wetting layer. nucleation time was found to be strongly influenced substrate temperature and more than 30 min for applied conditions. observed tapering reduced length silicon-doped explained enhanced nonpolar facets proves Ga-adatom diffusion nanorod...
The growth of α-Ga2O3 and α-(InxGa1−x)2O3 on m-plane α-Al2O3(101̄0) by molecular beam epitaxy (MBE) metal-oxide-catalyzed (MOCATAXY) is investigated. By systematically exploring the parameter space accessed MBE MOCATAXY, phase-pure α-Ga2O3(101̄0) α-(InxGa1−x)2O3(101̄0) thin films are realized. presence In surface remarkably expands its window far into metal-rich flux regime to higher temperatures. With increasing O-to-Ga ratio (RO), incorporates up x ≤ 0.08. Upon a critical thickness,...
We review the influence of GaN crystal polarity on various properties epitaxial films and electronic devices. grown sapphire by MOCVD or HVPE usually exhibit Ga-face polarity. N-face is obtained either backside such layers after removal from substrate, turning in MBE growth via a thin AlN buffer layer. In addition to rather obvious differences their structural morphological features, Ga- samples differ also properties. Thus, different Schottky barrier heights are observed for both...
Abstract The covalent attachment of small organic molecules and larger functional biomolecules such as DNA, enzymes, or other proteins on semiconductors is a new field basic research with pronounced interdisciplinary flavour. ultimate goal this endeavour the creation novel organic/inorganic heterostructures which can provide direct link between complex worlds biology digital electronics nanometer scale. purpose present survey to an overview over physics aspects, preparation methods, well...
Abstract The applicability of the group III nitride material system for fabrication semiconductor‐based biosensors is demonstrated. operation ion‐sensitive field‐effect transistors (ISFETs) based on AlGaN/GaN heterostructures in aqueous electrolytes shown to be characterized by high sensitivity and low drift. Fibroblasts contact with oxidized as‐deposited AlGaN surfaces are demonstrated survive at least 24 h, indicating that these chemically robust non‐toxic against living cells. Surface...
In the present article recent results concerning sensor applications of AlGaN layers and AlGaN/GaN heterostructures are summarized. The piezoresistive effect in piezoelectric is investigated dependence gauge factor on Al content attributed to influence strain induced fields. An enhancement this observed resulting high longitudinal factors. response gas sensitive Pt:GaN Schottky diodes hydrogen containing gases analyzed up temperatures 600 °C employed realize field transistors which...
The covalent functionalization of GaN and AlN surfaces with organosilanes is demonstrated. Both octadecyltrimethoxysilane aminopropyltriethoxysilane form self-assembled monolayers on hydroxylated surfaces, confirmed by x-ray photoelectron spectroscopy atomic force microscopy. monolayer thickness was determined to 2.5±0.2nm reflectivity. Temperature-programmed desorption measurements reveal a enthalpy 240kJ∕mol. realization micropatterned the hybridization deoxyribonucleic acid molecules...
An AlGaN∕GaN electrolyte gate field-effect transistor array for the detection of electrical cell signals has been realized. The low-frequency noise power spectral density these devices exhibits a 1∕f characteristic with dimensionless Hooge parameter 5×10−3. equivalent gate-input under operation conditions peak-to-peak amplitude 15μV, one order magnitude smaller than common silicon-based used extracellular recordings. Extracellular action potentials from confluent layer rat heart muscle cells...
Wurtzite Zn1−xMgxO thin films with Mg contents between x=0 and x=0.37 were grown on c-plane sapphire substrates by plasma assisted molecular beam epitaxy using a MgO/ZnMgO buffer layer. The a-lattice parameter is independent from the concentration, whereas c-lattice decreases 5.20 Å for to 5.17 x=0.37, indicating pseudomorphic growth. near band edge photoluminescence shows blueshift increasing concentration an emission energy of 4.11 eV x=0.37. Simultaneously, energetic position deep defect...
The optical properties of GaN nanowires grown by catalyst free plasma-assisted molecular beam epitaxy on Si (111) are investigated photoluminescence (PL) spectroscopy. influence the Si- and Mg-flux as well III-V ratio during growth PL is discussed. Mg concentration determined secondary ion mass spectroscopy ranges from 5×1018 to 1×1020 cm−3. Raman scattering reveals that strain-free, irrespective or Mg-doping. near band-edge emission undoped slightly Si-doped material dominated narrow D0X...
We report on the effect of Mg doping properties GaN nanowires grown by plasma assisted molecular beam epitaxy. The most significant feature is presence triple-twin domains, density which increases with increasing concentration. resulting high concentration misplaced atoms gives rise to local changes in crystal structure equivalent insertion three non-relaxed zinc-blende (ZB) atomic cells, result quantum wells along wurtzite (WZ) nanowire growth axis. High resolution electron energy loss...
The search for new wide-band-gap materials is intensifying to satisfy the need more advanced and energy-efficient power electronic devices. Ga2O3 has emerged as an alternative SiC GaN, sparking a renewed interest in its fundamental properties beyond main β-phase. Here, three polymorphs of Ga2O3, α, β, ε, are investigated using X-ray diffraction, photoelectron absorption spectroscopy, ab initio theoretical approaches gain insights into their structure–electronic structure relationships....
The DISS (DIrect Solar Steam) project is a complete R+TD program aimed at developing new generation of solar thermal power plants with direct steam (DSG) in the absorber tubes parabolic trough collectors. During first phase (1996-1998), life-size test facility was implemented Plataforma de Almerı´a (PSA) to investigate basic DSG processes under real conditions and evaluate unanswered technical questions concerning this technology. This paper updates status explains O&M-related experience...