A5061541362- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- Semiconductor Quantum Structures and Devices
- ZnO doping and properties
- Semiconductor materials and devices
- Strong Light-Matter Interactions
- Optical Coatings and Gratings
- Metal and Thin Film Mechanics
- Nanowire Synthesis and Applications
- Acoustic Wave Resonator Technologies
- Photonic Crystals and Applications
- Nuclear Physics and Applications
- Anodic Oxide Films and Nanostructures
- Photocathodes and Microchannel Plates
- Air Quality Monitoring and Forecasting
- Microfluidic and Capillary Electrophoresis Applications
- Advancements in Semiconductor Devices and Circuit Design
- Quantum and electron transport phenomena
- Silicon Carbide Semiconductor Technologies
- Particle accelerators and beam dynamics
- Advanced biosensing and bioanalysis techniques
- Spectroscopy and Laser Applications
- Biosensors and Analytical Detection
- Ion-surface interactions and analysis
- Nuclear physics research studies
Otto-von-Guericke University Magdeburg
2013-2024
Technical University of Munich
2017-2020
Technische Universität Berlin
2015
Rice University
2005
Baylor College of Medicine
2005
Carbon‐doping in the concentration range from [C] = 5 × 10 17 to 1.2 19 cm −3 is employed achieve semi‐insulating properties of GaN layers as required for electronic power devices. Using propane a carbon precursor, an independent analysis incorporation during growth and its impact on electrical was obtained parameters optimum quality could be applied. We observe that C within precision measurements fully incorporated compensating deep acceptor. In series Si + co‐doped samples, were > [Si]...
Intense emission from GaN islands embedded in AlN resulting GaN/AlN quantum well growth is directly resolved by performing cathodoluminescence spectroscopy a scanning transmission electron microscope. Line widths down to 440 μeV are measured wavelength region between 220 and 310 nm confirming dot like electronic properties the islands. These states can be structurally correlated of slightly enlarged thicknesses layer preferentially formed vicinity dislocations. The exhibit single photon...
We present an approach called pulsed multiline excitation (PME) for measurements of multicomponent, fluorescence species and demonstrate its application in capillary electrophoresis DNA sequencing. To fully the advantages PME, a fluorescent dye set has been developed whose absorption maxima span virtually entire visible spectrum. Unlike emission wavelength-dependent approaches identifying species, removal spectral component PME confers number including higher normalized signals from all dyes...
Strain in lattice matched and mismatched AlInN/GaN Bragg mirror structures were studied by situ curvature various ex x-ray measurements. In the case of considerable deviations in-plane parameters evidenced near surface region as well depth using grazing incidence transmission scattering Laue geometry. The experimental findings are explained terms partial stress relaxation layer stack with respect to underlying GaN buffer a mutual tensioning AlInN layers each other.
Different configurations of photoacoustic (PA) setups for the online-measurement gaseous N2O, employing semiconductor lasers at 2.9 and 4.5 μm, were developed tested. Their performance was assessed with respect to analysis N2O emissions from wastewater treatment plants. For this purpose, local a bioreactor sampled by dedicated mobile sampling device, total analyzed in gastight headspace bioreactor. We found that use quantum-cascade laser emitting about 4.53 operated wavelength modulation...
The luminescence properties of InxAl1−xN/GaN heterostructures are investigated systematically as a function the In content (x = 0.067 − 0.208). recombination between electrons confined in two-dimensional electron gas and free holes GaN template is identified analyzed. We find systematic shift with increasing from about 80 meV to only few below exciton emission. These results compared model calculations can be attributed changing band profile originating polarization gradient InAlN GaN.
Abstract We report on the growth of lattice‐matched AlInN/AlGaN distributed Bragg reflectors (DBRs) by metal‐organic vapor phase epitaxy. Growing these structures a AlGaN template, formation cracks was completely supressed and strain‐related structural degradations were avoided. A 35‐pair DBR provides peak reflectivity 99% at wavelength ∼360 nm with stop band width 18 nm. Thus, DBRs are well suited for application in high Q‐factor microcavities designed ultraviolet spectral region. However,...
InxGa1–xN/GaN single and multi quantum well (MQW) structures with x ≈ 0.13 were investigated optically by photoreflectance, photoluminescence excitation spectroscopy, luminescence. Clear evidence of unintentional indium incorporation into the nominal GaN barrier layers is found. The In content found to be around 3%. Inhomogeneous distribution atoms occurs within distinct (QW) layers, which commonly described as statistical alloy fluctuation leads characteristic S-shape temperature shift...
Low-strained AlInN/GaN multilayers aimed as Bragg mirrors were grown by metal organic vapour phase epitaxy on GaN/Si(1 1 1). In such structures the upper interfaces show a considerable roughening nanometre scale whereas lower ones appear flat evaluated cross-sectional electron and transmission microscopy. The is attributed to Stranski–Krastanov transition from two-dimensional layer-by-layer three-dimensional island growth. addition, self-organized wavy-like surface morphology micrometre...
Abstract We give direct evidence of distinct quantum dot states clustered but also spatially separated in single GaN islands. Resulting from layer growth on top AlN, the islands are predominantly formed close vicinity to threading dislocation bundles. Detailed analysis inner optical and structural properties, performed by nanoscale cathodoluminescence, reveals various sharp emission lines different regions an otherwise continuous island. Thickness fluctuations found within these made...
We report on metalorganic vapor phase epitaxy of highly conductive germanium-doped GaN layers and their application for blue tunnel-junction light emitting diodes (TJ-LEDs). Using Ge as donor, carrier densities up to 2 × 1020 cm−3 low bulk resistivities down 3 10−4 Ωcm are achieved. Under optimum growth conditions, no degradation the crystalline quality is observed exhibit high transparency making GaN:Ge very attractive current spreading layer in devices. have realized GaN-based TJ-LEDs by...
Using nano-cathodoluminescence performed in scanning transmission electron microscope (STEM-CL), we have investigated a photonic-bandgap-crystal (PBC) laser structure at T = 17 K. In cross-sectional STEM images the full device is clearly resolved. The most dominant luminescence originates from 3-fold MQW of active region. shows distinct peak wavelength change growth direction indicating different structural and/or chemical properties individual quantum wells. detail, clear shift 427 nm to...
Herein, integrating GaN quantum dots (QDs) within a resonant cavity is focused on. Utilizing metal‐organic vapor phase epitaxy, controlled growth of QDs on AlN achieved. A deep‐UV distributed Bragg reflector (DBR) with high reflectivity in the 250–300 nm range, using and Al 0.7 Ga 0.3 N layers to maximize refractive index contrast, developed. 50‐period DBR achieves 98% at wavelength 272 nm. Scanning transmission electron microscopy energy loss spectroscopy analyses reveal trisection periods,...
Model calculations have been performed to study systematically the formation of a two-dimensional electron gas (2DEG). The results are used for analyzing photoluminescence properties corresponding InAlN/GaN heterostructures (HS) various In concentrations ( x = 6.7–20.8%). We found luminescence peak, clearly dependent on content, that is attributed recombination between electrons in 2DEG at second level E n =2 ) and photoexcited holes GaN buffer. can be understood with changing band profile...
Abstract Effects of n-type doping Al 0.82 In 0.18 N/GaN heterostructures on the conduction band (CB) profile have been investigated. Doping concentrations well above 10 19 cm −3 are required to reduce large barriers in CB. Experimentally, Si- and Ge donor species compared for during metalorganic vapor phase epitaxy. For Si doping, we find substantial interface resistivity that will strongly contribute total device resistivity. AlInN is limited by either onset a self-compensation mechanism...
Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.
Abstract We report on the formation process of GaN/AlN quantum dots (QDs) which arises after deposition 1–2 monolayers GaN an AlN/sapphire template followed by a distinct growth interruption (GRI). The influence duration GRI structural and optical properties layer has been systematically investigated. QDs develop from initially bulky islands, nucleate in close vicinity to bundles threading dislocations (TDs). For prolonged GRIs, decreasing island size is observed consistent with systematic...
Journal Article Nanoscale Cathodoluminescence of an InGaN Single Quantum Well Intersected by Individual Dislocations Get access Gordon Schmidt, Schmidt Institute Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany Search for other works this author on: Oxford Academic Google Scholar Peter Veit, Veit Sebastian Metzner, Metzner Christoph Berger, Berger Frank Bertram, Bertram Armin Dadgar, Dadgar Andre Strittmatter, Strittmatter Jurgen Christen Microscopy and Microanalysis,...