Markus R. Wagner
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View article: Self‐Trapped Hole Migration and Defect‐Mediated Thermal Quenching of Luminescence in α‐ and β‐Ga<sub>2</sub>O<sub>3</sub>
Self‐Trapped Hole Migration and Defect‐Mediated Thermal Quenching of Luminescence in α‐ and β‐Ga<sub>2</sub>O<sub>3</sub> Open
Gallium oxide (Ga 2 O 3 ) is a promising ultrawide bandgap semiconductor for next‐generation power electronics and optoelectronic devices. Here, temperature‐dependent and polarization‐resolved photoluminescence excitation spectroscopy data…
View article: Multimode Emission in GaN Microdisk Lasers
Multimode Emission in GaN Microdisk Lasers Open
Quantum well nanolasers usually show single‐mode lasing, as gain saturation suppresses emissions in other modes. In contrast, for whispering gallery mode microdisk lasers with GaN quantum wells as active material, above threshold multimode…
View article: Anisotropy of optical transitions in <b> <i>β</i>-</b>Ga2O3 investigated by polarized photoluminescence excitation spectroscopy
Anisotropy of optical transitions in <b> <i>β</i>-</b>Ga2O3 investigated by polarized photoluminescence excitation spectroscopy Open
The monoclinic beta-phase of gallium oxide possesses an ultra-wide bandgap that surpasses other wide bandgap materials such as SiC and GaN, making it a promising candidate for power electronic device technologies. We investigate the first …
View article: Gain Characteristics of Optically Pumped UVC Lasers with Wide AlGaN Single‐Quantum‐Well Active Regions
Gain Characteristics of Optically Pumped UVC Lasers with Wide AlGaN Single‐Quantum‐Well Active Regions Open
Herein, the lasing threshold and gain characteristics of ultraviolet‐C optically pumped edge‐emitting lasers with thick single‐quantum‐well (SQW) active regions are investigated by the variable‐stripe length method. Positive net modal gain…
View article: Intercomparison of the finite difference and nodal discrete ordinates and surface flux transport methods for a LWR pool-reactor benchmark problem in X-Y geometry
Intercomparison of the finite difference and nodal discrete ordinates and surface flux transport methods for a LWR pool-reactor benchmark problem in X-Y geometry Open
The aim of the present work is to compare and discuss the three of the most advanced two dimensional transport methods, the finite difference and nodal discrete ordinates and surface flux method, incorporated into the transport codes TWODA…
View article: Epitaxial growth and characterization of multi-layer site-controlled InGaAs quantum dots based on the buried stressor method
Epitaxial growth and characterization of multi-layer site-controlled InGaAs quantum dots based on the buried stressor method Open
We report on the epitaxial growth, theoretical modeling, and structural as well as optical investigation of multi-layer, site-controlled quantum dots fabricated using the buried stressor method. This deterministic growth technique utilizes…
View article: Epitaxial growth and characterization of multi-layer site-controlled InGaAs quantum dots based on the buried stressor method
Epitaxial growth and characterization of multi-layer site-controlled InGaAs quantum dots based on the buried stressor method Open
We report on the epitaxial growth, theoretical modeling, and structural as well as optical investigation of multi-layer, site-controlled quantum dots fabricated using the buried stressor method. This advanced growth technique utilizes the …
View article: <i>In situ</i> study and modeling of the reaction kinetics during molecular beam epitaxy of GeO2 and its etching by Ge
<i>In situ</i> study and modeling of the reaction kinetics during molecular beam epitaxy of GeO2 and its etching by Ge Open
Rutile GeO2 has been predicted to be an ultra-wide bandgap semiconductor suitable for future power electronic devices, while quartz-like GeO2 shows piezoelectric properties. To explore these crystalline phases for application and fundament…
View article: Origin of the spectral red-shift and polarization patterns of self-assembled InGaN nanostructures on GaN nanowires
Origin of the spectral red-shift and polarization patterns of self-assembled InGaN nanostructures on GaN nanowires Open
A pronounced polarization anisotropy and spectral red-shift of the emission wavelength of individual InGaN nanowires is attributed to the spontaneous formation of superlattices caused by inhomogeneous In-distribution in the wires.
View article: CSD 2225080: Experimental Crystal Structure Determination
CSD 2225080: Experimental Crystal Structure Determination Open
An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely availabl…
View article: Silane‐Mediated Expansion of Domains in Si‐Doped κ‐Ga<sub>2</sub>O<sub>3</sub> Epitaxy and its Impact on the In‐Plane Electronic Conduction
Silane‐Mediated Expansion of Domains in Si‐Doped κ‐Ga<sub>2</sub>O<sub>3</sub> Epitaxy and its Impact on the In‐Plane Electronic Conduction Open
Unintentionally doped (001)‐oriented orthorhombic κ‐Ga 2 O 3 epitaxial films on c‐plane sapphire substrates are characterized by the presence of ≈ 10 nm wide columnar rotational domains that can severely inhibit in‐plane electronic conduct…
View article: Tackling Disorder in γ‐Ga<sub>2</sub>O<sub>3</sub>
Tackling Disorder in γ‐Ga<sub>2</sub>O<sub>3</sub> Open
Ga 2 O 3 and its polymorphs are attracting increasing attention. The rich structural space of polymorphic oxide systems such as Ga 2 O 3 offers potential for electronic structure engineering, which is of particular interest for a range of …
View article: Anisotropic thermoreflectance thermometry: A contactless frequency-domain thermoreflectance approach to study anisotropic thermal transport
Anisotropic thermoreflectance thermometry: A contactless frequency-domain thermoreflectance approach to study anisotropic thermal transport Open
We developed a novel contactless frequency-domain thermoreflectance approach to study thermal transport, which is particularly convenient when thermally anisotropic materials are considered. The method is based on a line-shaped heater geom…
View article: First and Second Order Raman Spectroscopy of Monoclinic $β-\mathrm{Ga}_2\mathrm{O}_{3}$
First and Second Order Raman Spectroscopy of Monoclinic $β-\mathrm{Ga}_2\mathrm{O}_{3}$ Open
We employ a combined experimental-theoretical study of the first- and second-order Raman modes of monoclinic $β$-Ga$_{2}$O$_{3}$. The investigated materials is of particular interest due to its deep-UV bandgap paired with a high critical f…
View article: Anisotropic Thermoreflectance Thermometry: A contactless frequency-domain approach to study anisotropic thermal transport
Anisotropic Thermoreflectance Thermometry: A contactless frequency-domain approach to study anisotropic thermal transport Open
We developed a novel contactless frequency-domain approach to study thermal transport, which is particularly convenient when thermally anisotropic materials are considered. The method is based on a similar line-shaped heater geometry as us…
View article: Isotopic study of Raman active phonon modes in β-Ga<sub>2</sub>O<sub>3</sub>
Isotopic study of Raman active phonon modes in β-Ga<sub>2</sub>O<sub>3</sub> Open
The Raman-active phonon modes of β-Ga2O3 in two O isotope compositions are studied by theory and experiment. Raman modes dominated by different, inequivalent O lattice sites were identified and can be used for the investigation of point de…
View article: Hidden polymorphism of FAPbI<sub>3</sub> discovered by Raman spectroscopy
Hidden polymorphism of FAPbI<sub>3</sub> discovered by Raman spectroscopy Open
Formamidinium lead iodide (FAPbI 3 ) can exhibit polymorphism at ambient conductions. Three different structural configurations and their thermally activated phase transitions are identified by temperature dependent micro-Raman spectroscop…
View article: Comprehensive Raman study of orthorhombic κ/ε-Ga<sub>2</sub>O<sub>3</sub>and the impact of rotational domains
Comprehensive Raman study of orthorhombic κ/ε-Ga<sub>2</sub>O<sub>3</sub>and the impact of rotational domains Open
The Raman-active phonon modes of orthorhombic gallium oxide (κ/ε-Ga 2 O 3 ) are investigated by combination of polarized micro-Raman spectroscopy and density functional perturbation theory (DFPT) calculations.
View article: A 310 nm Optically Pumped AlGaN Vertical-Cavity Surface-Emitting Laser
A 310 nm Optically Pumped AlGaN Vertical-Cavity Surface-Emitting Laser Open
Ultraviolet light is essential for disinfection, fluorescence excitation, curing, and medical treatment. An ultraviolet light source with the small footprint and excellent optical characteristics of vertical-cavity surface-emitting lasers …
View article: Strong Near-Field Light–Matter Interaction in Plasmon-Resonant Tip-Enhanced Raman Scattering in Indium Nitride
Strong Near-Field Light–Matter Interaction in Plasmon-Resonant Tip-Enhanced Raman Scattering in Indium Nitride Open
We report a detailed study of the strong near-field Raman scattering enhancement, which takes place in tip-enhanced Raman scattering (TERS) in indium nitride. In addition to the well-known first-order optical phonons of indium nitride, nea…
View article: Influence of Polymorphism on the Electronic Structure of Ga<sub>2</sub>O<sub>3</sub>
Influence of Polymorphism on the Electronic Structure of Ga<sub>2</sub>O<sub>3</sub> Open
The search for new wide-band-gap materials is intensifying to satisfy the need for more advanced and energy-efficient power electronic devices. Ga2O3 has emerged as an alternative to SiC and GaN, sparking a renewed interest in its fundamen…
View article: Isotopic study of Raman active phonon modes in $β$-Ga$_{2}$O$_{3}$
Isotopic study of Raman active phonon modes in $β$-Ga$_{2}$O$_{3}$ Open
Holding promising applications in power electronics, the wide band gap material gallium oxide has emerged as a vital alternative to materials like GaN and SiC. The detailed study of phonon modes in $β$-Ga$_{2}$O$_{3}$ provides insights int…
View article: Isotopic study of Raman active phonon modes in $\beta$-Ga$_{2}$O$_{3}$
Isotopic study of Raman active phonon modes in $\beta$-Ga$_{2}$O$_{3}$ Open
Holding promising applications in power electronics, the wide band gap\nmaterial gallium oxide has emerged as a vital alternative to materials like GaN\nand SiC. The detailed study of phonon modes in $\\beta$-Ga$_{2}$O$_{3}$ provides\ninsi…
View article: Phononic and photonic semiconductor nanostructures
Phononic and photonic semiconductor nanostructures Open
Semiconductor nanostructures form the basic building blocks for the majority of modern electronic and photonic components. The continuous reduction of their dimensions in the past decades has opened possibilities to manipulate phononic and…
View article: Vibrational dynamics in lead halide hybrid perovskites investigated by Raman spectroscopy
Vibrational dynamics in lead halide hybrid perovskites investigated by Raman spectroscopy Open
The effect of the incorporation of Cs+ and Br− in FAPbl3 investigated by Raman spectroscopy.