K. Irmscher
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View article: Properties of a highly compensated high-purity germanium
Properties of a highly compensated high-purity germanium Open
The electrical and optical properties of a compensated high-purity germanium (HPGe) single crystal was investigated using various characterization techniques. Aluminium, boron, and phosphorus were the major residual shallow-level impuritie…
View article: Thermal Stability of Schottky Contacts and Rearrangement of Defects in <i>β</i>‐Ga<sub>2</sub>O<sub>3</sub> Crystals
Thermal Stability of Schottky Contacts and Rearrangement of Defects in <i>β</i>‐Ga<sub>2</sub>O<sub>3</sub> Crystals Open
The thermal stability of different Schottky contacts (Au, Pt, and Ni) on (100) β ‐Ga 2 O 3 single crystals grown by the Czochralski method is investigated. Besides the examination of the Schottky barrier parameters, contact‐dependent defec…
View article: Charge state transition levels of Ni in <i>β</i>-Ga2O3 crystals from experiment and theory: An attractive candidate for compensation doping
Charge state transition levels of Ni in <i>β</i>-Ga2O3 crystals from experiment and theory: An attractive candidate for compensation doping Open
Nickel-doped β-Ga2O3 crystals were investigated by optical absorption and photoconductivity, revealing Ni-related deep levels. The photoconductivity spectra were fitted using the phenomenological Kopylov and Pikhtin model to identify the e…
View article: Comparative Raman spectroscopy of astrobiology relevant bio‐samples and planetary surface analogs under UV–VIS–IR excitation
Comparative Raman spectroscopy of astrobiology relevant bio‐samples and planetary surface analogs under UV–VIS–IR excitation Open
We investigated the potential of a laser selection in the broad optical range, from ultraviolet through visible to infrared (excitation wavelengths of 325, 532, 785, and 1064 nm) for combined analysis of Earth‐relevant extremophiles ( Xant…
View article: Silicon diffusion in AlN
Silicon diffusion in AlN Open
In this study, we investigate the diffusion of Si donors in AlN. Amorphous Si1−xNx sputtered on the surface of bulk AlN with low dislocation density is used as a Si source. The diffusion experiments are conducted through isochronal and iso…
View article: Development of Large‐Diameter and Very High Purity Ge Crystal Growth Technology for Devices
Development of Large‐Diameter and Very High Purity Ge Crystal Growth Technology for Devices Open
High‐purity germanium (HPGe) single crystals find their applications as radiation detectors especially for spectroscopy of high‐energy photons and particles in nuclear physics. Growing “detector‐grade” HPGe single crystals, with tailored s…
View article: Suppression of particle formation by gas-phase pre-reactions in (100) MOVPE-grown <b> <i>β</i> </b>-Ga2O3 films for vertical device application
Suppression of particle formation by gas-phase pre-reactions in (100) MOVPE-grown <b> <i>β</i> </b>-Ga2O3 films for vertical device application Open
This work investigated the metalorganic vapor-phase epitaxy (MOVPE) of (100) β-Ga2O3 films with the aim of meeting the requirements to act as drift layers for high-power electronic devices. A height-adjustable showerhead achieving a close …
View article: Bulk single crystals and physical properties of β-(AlxGa1−x)2O3 (x = 0–0.35) grown by the Czochralski method
Bulk single crystals and physical properties of β-(AlxGa1−x)2O3 (x = 0–0.35) grown by the Czochralski method Open
We have systematically studied the growth, by the Czochralski method, and basic physical properties of a 2 cm and 2 in. diameter bulk β-(AlxGa1−x)2O3 single crystal with [Al] = 0–35 mol. % in the melt in 5 mol. % steps. The segregation coe…
View article: Cobalt as a promising dopant for producing semi-insulating <i>β</i>-Ga2O3 crystals: Charge state transition levels from experiment and theory
Cobalt as a promising dopant for producing semi-insulating <i>β</i>-Ga2O3 crystals: Charge state transition levels from experiment and theory Open
Optical absorption and photoconductivity measurements of Co-doped β-Ga2O3 crystals reveal the photon energies of optically excited charge transfer between the Co related deep levels and the conduction or valence band. The corresponding pho…
View article: Low temperature thermoluminescence of β-Ga2O3 scintillator
Low temperature thermoluminescence of β-Ga2O3 scintillator Open
Low temperature thermoluminescence of β-Ga2O3, β-Ga2O3:Al and β-Ga2O3:Ce has been investigated. Glow curves have been analyzed quantitatively using a rate equations model in order to determine the traps parameters, such as activation energ…
View article: Si doping mechanism in MOVPE-grown (100) <b>β</b>-Ga2O3 films
Si doping mechanism in MOVPE-grown (100) <b>β</b>-Ga2O3 films Open
A Langmuir adsorption model of the Si incorporation mechanism into metalorganic vapor-phase epitaxy grown (100) β-Ga2O3 thin films is proposed in terms of the competitive surface adsorption process between Si and Ga atoms. The outcome of t…
View article: Heading for brighter and faster β-Ga2O3 scintillator crystals
Heading for brighter and faster β-Ga2O3 scintillator crystals Open
Czochralski-grown β-Ga2O3 and β-Ga2O3:Si crystals with the free electron concentrations between 2.5·1016 and 4.3·1018 cm−3 have been characterized by means of pulse height and scintillation time profile measurements in order to assess thei…
View article: Two inch diameter, highly conducting bulk <b> <i>β</i> </b>-Ga2O3 single crystals grown by the Czochralski method
Two inch diameter, highly conducting bulk <b> <i>β</i> </b>-Ga2O3 single crystals grown by the Czochralski method Open
Two inch diameter, highly conducting (Si-doped) bulk β-Ga2O3 single crystals with the cylinder length up to one inch were grown by the Czochralski method. The obtained crystals revealed high structural quality characterized by narrow x-ray…
View article: Terahertz electron paramagnetic resonance generalized spectroscopic ellipsometry: The magnetic response of the nitrogen defect in 4H-SiC
Terahertz electron paramagnetic resonance generalized spectroscopic ellipsometry: The magnetic response of the nitrogen defect in 4H-SiC Open
We report on terahertz (THz) electron paramagnetic resonance generalized spectroscopic ellipsometry (THz-EPR-GSE). Measurements of field and frequency dependencies of magnetic response due to spin transitions associated with nitrogen defec…
View article: A consistent picture of excitations in cubic BaSnO3 revealed by combining theory and experiment
A consistent picture of excitations in cubic BaSnO3 revealed by combining theory and experiment Open
View article: Resonant electronic Raman scattering from Ir4+ ions in <i>β</i>-Ga2O3
Resonant electronic Raman scattering from Ir4+ ions in <i>β</i>-Ga2O3 Open
We report the observation of resonant electronic Raman scattering (ERS) originating from Ir4+ ions in bulk β-Ga2O3 crystals grown by the Czochralski method. The observed ERS peak at 5150 cm−1 at room temperature is attributed to an interna…
View article: Toward Precise n-Type Doping Control in MOVPE-Grown β-Ga2O3 Thin Films by Deep-Learning Approach
Toward Precise n-Type Doping Control in MOVPE-Grown β-Ga2O3 Thin Films by Deep-Learning Approach Open
In this work, we train a hybrid deep-learning model (fDNN, Forest Deep Neural Network) to predict the doping level measured from the Hall Effect measurement at room temperature and to investigate the doping behavior of Si dopant in both (1…
View article: Experimental and Theoretical Investigation of the Surface Electronic Structure of ZnGa<sub>2</sub>O<sub>4</sub>(100) Single‐Crystals
Experimental and Theoretical Investigation of the Surface Electronic Structure of ZnGa<sub>2</sub>O<sub>4</sub>(100) Single‐Crystals Open
Herein, a detailed experimental and theoretical investigation on the surface electronic structure of ZnGa 2 O 4 (100) bulk single‐crystals, with a special emphasis on the surface preparation, is presented. The surface crystallizes in the b…
View article: <i>In-situ</i> TEM Observations of Resistance Switching in Strontium Titanate Devices
<i>In-situ</i> TEM Observations of Resistance Switching in Strontium Titanate Devices Open
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View article: Fast homoepitaxial growth of (100) β-Ga2O3 thin films via MOVPE
Fast homoepitaxial growth of (100) β-Ga2O3 thin films via MOVPE Open
A high growth rate process above 1 µm/h was achieved for Si-doped (100) β-Ga2O3 homoepitaxial films grown via metalorganic vapor phase epitaxy (MOVPE) while maintaining high crystalline perfection up to a film thickness of 3 µm. The main g…
View article: Experimental Hall electron mobility of bulk single crystals of transparent semiconducting oxides
Experimental Hall electron mobility of bulk single crystals of transparent semiconducting oxides Open
View article: Current Status of Carbon‐Related Defect Luminescence in GaN
Current Status of Carbon‐Related Defect Luminescence in GaN Open
Highly insulating layers are a prerequisite for gallium nitride (GaN)‐based power electronic devices. For this purpose, carbon doping is one of the currently pursued approaches. However, its impact on the optical and electrical properties …
View article: A carbon-doping related luminescence band in GaN revealed by below bandgap excitation
A carbon-doping related luminescence band in GaN revealed by below bandgap excitation Open
Carbon doped GaN grown by hydride vapor phase epitaxy was investigated by photoluminescence and photoluminescence excitation spectroscopy covering a broad range of carbon concentrations. Above bandgap excitation reveals typical transitions…
View article: Recent progress in the development of β-Ga<sub>2</sub>O<sub>3</sub> scintillator crystals grown by the Czochralski method
Recent progress in the development of β-Ga<sub>2</sub>O<sub>3</sub> scintillator crystals grown by the Czochralski method Open
A high-quality bulk single crystal of β-Ga 2 O 3 has been grown by the Czochralski method and its basic scintillation characteristics (light yield, energy resolution, proportionality, and scintillation decay times) have been investigated. …
View article: Melt Growth and Physical Properties of Bulk LaInO<sub>3</sub> Single Crystals
Melt Growth and Physical Properties of Bulk LaInO<sub>3</sub> Single Crystals Open
Large bulk LaInO 3 single crystals are grown from the melt contained within iridium crucibles by the vertical gradient freeze (VGF) method. The obtained crystals are undoped or intentionally doped with Ba or Ce, and enabled wafer fabricati…
View article: Optical phonon modes, static and high-frequency dielectric constants, and effective electron mass parameter in cubic In2O3
Optical phonon modes, static and high-frequency dielectric constants, and effective electron mass parameter in cubic In2O3 Open
A complete set of all optical phonon modes predicted by symmetry for bixbyite structure indium oxide is reported here from a combination of far-infrared and infrared spectroscopic ellipsometry, as well as first principles calculations. Die…
View article: Excitations in cubic BaSnO$_{3}$: a consistent picture revealed by combining theory and experiment
Excitations in cubic BaSnO$_{3}$: a consistent picture revealed by combining theory and experiment Open
Among the transparent conducting oxides, the perovskite barium stannate is the most promising candidate for various electronic applications due to its outstanding carrier mobility achieved at room temperature. Experimental reports on its c…
View article: Influence of Sr deficiency on structural and electrical properties of SrTiO3 thin films grown by metal–organic vapor phase epitaxy
Influence of Sr deficiency on structural and electrical properties of SrTiO3 thin films grown by metal–organic vapor phase epitaxy Open
View article: Fingerprints of optical absorption in the perovskite <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">LaInO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>: Insight from many-body theory and experiment
Fingerprints of optical absorption in the perovskite : Insight from many-body theory and experiment Open
We provide a combined theoretical and experimental study of the electronic\nstructure and the optical absorption edge of the orthorhombic perovskite\nLaInO$_{3}$. Employing density-functional theory and many-body perturbation\ntheory, we p…
View article: The anisotropic quasi-static permittivity of single-crystal beta-Ga2O3
The anisotropic quasi-static permittivity of single-crystal beta-Ga2O3 Open
The quasi-static anisotropic permittivity parameters of electrically insulating gallium oxide (beta-Ga2O3) were determined by terahertz spectroscopy. Polarization-resolved frequency domain spectroscopy in the spectral range from 200 GHz to…