A5044084996- GaN-based semiconductor devices and materials
- Silicon Carbide Semiconductor Technologies
- Ga2O3 and related materials
- Acoustic Wave Resonator Technologies
- Semiconductor materials and devices
- ZnO doping and properties
- Advanced ceramic materials synthesis
- Silicon and Solar Cell Technologies
- Thin-Film Transistor Technologies
- Electronic and Structural Properties of Oxides
- Microwave Dielectric Ceramics Synthesis
- Metal and Thin Film Mechanics
- Semiconductor Quantum Structures and Devices
- Copper Interconnects and Reliability
- Advanced Photocatalysis Techniques
- Ferroelectric and Piezoelectric Materials
- Aluminum Alloys Composites Properties
- Thermal properties of materials
- Luminescence Properties of Advanced Materials
- Photorefractive and Nonlinear Optics
- Glass properties and applications
- Semiconductor materials and interfaces
- Advanced Surface Polishing Techniques
- Magnetic and transport properties of perovskites and related materials
- Induction Heating and Inverter Technology
Leibniz Institute for Crystal Growth
2016-2025
Technische Universität Berlin
2014-2025
Friedrich-Alexander-Universität Erlangen-Nürnberg
2004-2013
Otto-von-Guericke University Magdeburg
2013
L3S Research Center
1998-2009
We present a new approach for scaling-up the growth of β-Ga2O3 single crystals grown from melt by Czochralski method, which has also direct application to other melt-growth techniques involving noble metal crucible. Experimental and theoretical results point thermodynamics as crucial factor in increasing volume growing crystal. In particular, formation metallic gallium liquid phase large volumes causes problems with crystal eutectic or intermetallic The larger be higher oxygen concentration...
Photoluminescence spectra of high-quality bulk AlN crystals are reported. In addition to the expected linear luminescence features like free excitons and donor-bound excitons, nonlinear processes biexcitons exciton-exciton scattering band seen for higher excitation densities. For temperatures above $\ensuremath{\approx}150\text{ }\text{K}$ electron-hole plasma becomes clearly visible in spectra. A detailed analysis data yields an exciton binding energy 55 meV, a biexciton 28.5 gap 6.089 eV...
The performance characteristics of optically pumped laser heterostructures emitting in the UV-C spectral range between 272 and 279 nm are investigated. were grown by metal-organic vapor phase epitaxy on (0001) planar AlN/sapphire, epitaxially laterally overgrown (ELO) bulk AlN substrates with threading dislocation densities ranging from 2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> to 10...
The process technologies of AlN growth by physical vapour transport are reviewed in this paper with a focus on the parameters, crucible materials, and type seeding/nucleation. In context three strategies for first generation seeds, (i) grain selection, (ii) heteroepitaxially seeding SiC, (iii) spontaneous nucleation, evaluated regarding their impact structural properties sizes grown crystals. Major issues subsequent homoepitaxial runs controlled diameter enlargement, such as thermal field...
Truly bulk ZnGa2O4 single crystals were obtained directly from the melt. High melting point of 1900 ± 20 °C and highly incongruent evaporation Zn- Ga-containing species impose restrictions on growth conditions. The are characterized by a stoichiometric or near-stoichiometric composition with normal spinel structure at room temperature narrow full width half maximum rocking curve 400 peak (100)-oriented samples 23 arcsec. is crystalline phase Ga/Zn atomic ratio up to about 2.17. Melt-grown...
Two inch diameter, highly conducting (Si-doped) bulk β-Ga2O3 single crystals with the cylinder length up to one were grown by Czochralski method. The obtained revealed high structural quality characterized narrow x-ray rocking curves (FWHM ≤ 25 arc sec) and surface smoothness (RMS &lt; 200 pm) of epi-ready wafers. free electron concentration Hall mobility at room temperature in range 1.6–9 × 1018 cm−3 118 – 52 cm2 V−1 s−1, respectively, which are not affected a heat treatment...
Freestanding AlN single crystals are grown in a RF-heated furnace by physical vapor transport (PVT). Three different growth regimes with temperatures between 2080–2200°C result crystal habits and very high structural quality. The Rocking curves show FWHM < 21 arcsec the 0002 101̄0 Reflection on as-grown facets. Isometric sizes up to 10 × 12mm 3 zonar structure consisting of yellowish core area which is N-polar (0001̄) facet nearly colorless edge region prismatic {101̄0} In two zones same...
Bulk MgGa2O4 single crystals with inverse spinel structure were grown from the melt by different methods. The degree of inversion could be changed suitable annealing, which was confirmed differential scanning calorimetry analysis and corresponding changes specific heat capacity. is thermally much more stable at high temperatures than β-Ga2O3 despite a higher melting point about 1930 °C under neutral atmosphere. Melt-grown found to either electrical insulators or n-type semiconductors...
In this paper, the optimal growth conditions during physical vapour transport of bulk AlN crystals are evaluated with regard to significantly increased deep UV transparency, while maintaining high structural quality which grown on N-polar c-facets. We show that carbon concentration [C], oxygen [O], and ratio between both concentrations [C]/[O] have a significant influence transparency. At 3[C] < [O] [C] + 1019 cm−3, transparent single absorption coefficients at around 265 nm (α265nm) smaller...
The thermal conductivity of AlN single crystals grown by physical vapor transport (PVT) and hydride phase epitaxy (HVPE) was measured in the range 30 to 325 K 3ω method. room-temperature ranged from 268 374 W m−1 K−1. Higher correlated with higher transparency at 265 nm lower total impurity levels.
We have systematically studied the growth, by Czochralski method, and basic physical properties of a 2 cm in. diameter bulk β-(AlxGa1−x)2O3 single crystal with [Al] = 0–35 mol. % in melt 5 steps. The segregation coefficient Al Ga2O3 1.1–1.2 results higher content crystals than melt. were also co-doped Si or Mg. 30 (33–36 crystals) seems to be limit for obtaining high structural quality suitable homoepitaxy. either semiconducting (no intentional co-dopants 0–30 Si-doped 15–20 %), degenerately...
Specific heat capacity measurements by differential scanning calorimetry (DSC) of single crystals solid solutions LiNbO3 and LiTaO3 are reported compared with corresponding ab initio calculations, the aim to investigate variation ferroelectric Curie temperature as a function composition. For this purpose, these were grown Czochralski pulling along c-axis. Elemental composition Nb Ta was investigated using XRF analysis, small samples homogeneous well known used for DSC measurements. We...
The intrinsic anisotropic optical properties of wurtzite AlN are investigated in absorption and emission. Full access to the anisotropy response hexagonal material is obtained by investigating $(1\overline{1}00)$ plane a high-quality bulk crystal allowing electric field $\mathbf{E}$ polarization perpendicular ($\mathbf{E}\ensuremath{\perp}\mathbf{c}$) parallel ($\mathbf{E}\ensuremath{\parallel}\mathbf{c}$) axis $\mathbf{c}$. Spectroscopic ellipsometry yields ordinary...
We have investigated the effect of doping on absorption for various SiC polytypes, i.e., n-type (N) 6H–SiC, 4H–SiC, and 15R–SiC, p-type (Al) (B) 6H–SiC. For these polytypes band-gap narrowing with higher concentration is observed. In addition, below bands at 464 nm 623 422 734 15R–SiC are The peak intensities show a linear relation to charge carrier obtained from Hall measurements. corresponding calibration factors given. As an application purely optical wafer mapping spatial variation demonstrated.
Abstract Bulk aluminum nitride (AlN) is a very promising substrate material for UV optoelectronics, and its transparency of high interest devices designed to emit through the substrate. We report on 500 μm thick bulk AlN substrates with plain transmittance exceeding 50% (i.e., absorption coefficients below 14 cm –1 ) wavelengths from 220 nm 380 in main wafer area. Comparing spectra different samples, four major band‐gap bands are identified interpreted based point defect model crystals....
In unintentionally Si-doped AlN, the electron paramagnetic resonance (EPR) spectrum of Si shallow donor (g=1.9905) was observed in darkness at room temperature. The temperature dependence EPR signal suggests that AlN is a DX center with DX− state lying ∼78 meV below neutral state. With such relatively small thermal activation energy, expected to behave as dopant normal device operating temperatures.
Abstract The surface of bulk AlN single crystals grown by PVT on Al‐polar (0001) seeds is typically constructed from prismatic, pyramidal, and basal plane facets. Simultaneous growth different facets with kinetics leads to formation a zonar structure which visible due local differences in coloration the wafers. Four zones an wafer representing (1) {10 1 3} pyramidal facets, (2) adjacent ridges (3) + (4) outer centre areas corresponding depressions are investigated. They show striking optical...
Abstract SnO 2 is a semiconductor with wide optical bandgap (3.5 eV), which makes it an attractive transparent semiconducting oxide (TSO) for electronic and opto‐electronic applications. At elevated temperatures is, however, much more unstable than other TSOs (such as ZnO, Ga O 3 , or In ). This leads to rapid decomposition even under very high oxygen pressures. Our experiments showed that stoichiometric does not melt up 2100 °C, in contradiction earlier published data. Bulk single crystals,...
A high seed temperature (2251 °C) reveals the highest deep UV transparency (<italic>α</italic><sub>265nm</sub> = 27 cm<sup>−1</sup>), a structural perfection (EPD 9 × 10<sup>3</sup> cm<sup>−2</sup>) and suitable growth rate (<italic>R</italic> 200 μm h<sup>−1</sup>).