The quasi-static anisotropic permittivity parameters of electrically insulating beta gallium oxide (β-Ga2O3) were determined by terahertz spectroscopy. Polarization-resolved frequency domain spectroscopy in the spectral range from 200 GHz to 1 THz was carried out on bulk crystals along different orientations. Principal directions for crystallographic axes c and b reciprocal lattice direction a*. No significant dispersion real part dielectric observed measured range. Our results are excellent...

Electron effective mass is a fundamental material parameter defining the free charge carrier transport properties, but it very challenging to be experimentally determined at high temperatures relevant device operation. In this work, we obtain electron parameters in Si-doped GaN bulk substrate and epitaxial layers from terahertz (THz) mid-infrared (MIR) optical Hall effect (OHE) measurements temperature range of 38–340 K. The OHE data are analyzed using well-accepted Drude model account for...

We demonstrate detection and measurement of electron paramagnetic spin resonances (EPR) iron defects in <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>β</a:mi><a:mtext>−</a:mtext><a:msub><a:mi>Ga</a:mi><a:mn>2</a:mn></a:msub><a:msub><a:mi mathvariant="normal">O</a:mi><a:mn>3</a:mn></a:msub></a:mrow></a:math> utilizing generalized ellipsometry at frequencies between 110 170 GHz. The experiments are performed on an Fe-doped single crystal a free-beam configuration...

We use a combined generalized spectroscopic ellipsometry and density functional theory approach to determine analyze the anisotropic dielectric functions of an $\alpha$-Ga$_2$O$_3$ thin film. The sample is grown epitaxially by plasma-assisted molecular beam epitaxy on $m$-plane sapphire. Generalized data from multiple azimuths in spectral range 0.73 eV 8.75 are simultaneously analyzed. Density used calculate valence conduction band structure. identify, for indirect-bandgap material, two...

We report on terahertz (THz) electron paramagnetic resonance generalized spectroscopic ellipsometry (THz-EPR-GSE). Measurements of the field and frequency dependencies magnetic response due to spin transitions associated with nitrogen defect in 4H-SiC are shown as an example. THz-EPR-GSE dispenses need a cavity, permits independently scanning parameters, does not require or modulation. investigate hexagonal ($h$) cubic ($k$) coordinated including coupling its nuclear (I=1), we propose model...

We determine the anisotropic dielectric functions of rhombohedral $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ by far-infrared and infrared generalized spectroscopic ellipsometry derive all transverse optical longitudinal phonon mode frequencies broadening parameters. also high-frequency static constants. perform density functional theory computations dispersion for branches in Brillouin zone, we parameters at zone center including Raman-active,...

A complete set of all optical phonon modes predicted by symmetry for bixbyite structure indium oxide is reported here from a combination far-infrared and infrared spectroscopic ellipsometry, as well first principle calculations. Dielectric function spectra measured on high quality, marginally electrically conductive melt grown single bulk crystals are obtained wavelength-by-wavelength (a.k.a. point-by-point) basis numerical reduction subtle free charge carrier Drude model contribution....

Mueller matrix spectroscopic ellipsometry is applied to determine anisotropic optical properties for a set of single-crystal rhombohedral structure α-(AlxGa1−x)2O3 thin films (0 ≤ x 1). Samples are grown by plasma-assisted molecular beam epitaxy on m-plane sapphire. A critical-point model used render dielectric function tensor and direct electronic band-to-band transition parameters, including the direction dependent two lowest-photon energy transitions associated with bandgap. We obtain...

The anisotropic permittivity parameters of monoclinic single crystal lutetium oxyorthosilicate, Lu2SiO5 (LSO), have been determined in the terahertz spectral range. Using generalized spectroscopic ellipsometry (THz-GSE), we obtained THz permittivities along a, b, and c⋆ directions, which correspond to εa, εb, εc⋆ on-diagonal tensor elements. associated off diagonal element εac⋆ was also experimentally, is required describe LSO's optical response a–c crystallographic plane. From four elements...

A unique class of advanced materials-quantum composites based on polymers with fillers composed a van der Waals quantum material that reveals multiple charge-density-wave condensate phases-is demonstrated. Materials exhibit phenomena are typically crystalline, pure, and have few defects because disorder destroys the coherence electrons phonons, leading to collapse states. The macroscopic phases filler particles after composite processing steps successfully preserved in this work. prepared...

Strain-stress relationships for physical properties are of interest heteroepitaxial material systems, where strain and stress inherent due to thermal expansion lattice mismatch. We report linear perturbation theory optical phonon modes in monoclinic crystals situations which maintain the symmetry crystal. By using group analysis frequencies obtained under various deformation scenarios from density-functional calculations on...

A Mueller matrix spectroscopic ellipsometry approach was used to investigate the anisotropic dielectric constants of corundum α-(AlxGa1−x)2O3 thin films in their below bandgap spectral regions. The sample set epitaxially grown using plasma-assisted molecular beam epitaxy on m-plane sapphire. measurements were performed at multiple azimuthal angles resolve uniaxial properties. Cauchy dispersion model applied, and high-frequency are determined for polarization perpendicular (ε∞,⊥) parallel...

We report the strain and stress relationships for three lowest energy direct band to transitions at Brillouin zone center in monoclinic β-Ga2O3. These augment four linear perturbation parameters situations, which maintain symmetry, are reported here as numerical values obtained from density functional theory calculations. With knowledge of these parameters, shift each transition energies can be predicted specific state or stress, thus providing a useful tool modeling performance power...

We report the elevated temperature (22 °C ≤ T 600 °C) dielectric function properties of melt grown single crystal ZnGa2O4 using a spectroscopic ellipsometry approach. A dependent Cauchy dispersion analysis was applied across transparent spectrum to determine high-frequency index refraction yielding slope 3.885(2) × 10−5 K−1. model critical point examine and transitions for each temperature. The lowest energy M0-type associated with direct bandgap transition in is shown red-shift linearly as...

A complete set of infrared-active and Raman-active lattice modes is obtained from density functional theory calculations for single-crystalline centrosymmetric orthorhombic neodymium gallate. The results are compared with an analysis the anisotropic long-wavelength properties using generalized spectroscopic ellipsometry. frequency-dependent dielectric function tensor loss gallium oxide reported in spectral range $80--1200\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. combined...

A combined generalized spectroscopic ellipsometry measurement and density functional theory calculation analysis is performed to obtain the complete set of infrared active phonon modes in Lu$_{2}$SiO$_{5}$ with monoclinic crystal structure. Two different crystals, each cut perpendicular a axis are investigated. Ellipsometry measurements from 40 - 1200 cm$^{-1}$ used determine frequency dependent dielectric function tensor elements. The eigendielectric displacement vector summation approach...

We determine the dielectric function of emerging ultrawide bandgap semiconductor ZnGa2O4 from near-infrared (0.75 eV) into vacuum ultraviolet (8.5 spectral regions using spectroscopic ellipsometry on high quality single crystal substrates. perform density functional theory calculations and discuss band structure Brillouin zone Γ-point band-to-band transition energies, their matrix elements, effective mass parameters. find an isotropic parameter (0.24 me) at bottom conduction band, which...

We determine the composition dependence of transverse and longitudinal optical infrared-active phonon modes in rhombohedral α-(AlxGa1−x)2O3 alloys by far-infrared infrared generalized spectroscopic ellipsometry. Single-crystalline high quality undoped thin-films grown on m-plane oriented α-Al2O3 substrates with x = 0.18, 0.37, 0.54 were investigated. A single mode behavior is observed for all modes, i.e., their frequencies shift gradually between equivalent isostructural binary parent...

The bowing of the energy three lowest band-to-band transitions in $\ensuremath{\beta}\text{\ensuremath{-}}({\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}{)}_{2}{\mathrm{O}}_{3}$ alloys is resolved using a combined density-functional theory (DFT) and generalized spectroscopic ellipsometry approach. DFT calculations electronic band structure both $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$...

Infrared-active lattice mode properties of melt-grown high-quality single bulk crystals ZnGa2O4 are investigated by combined spectroscopic ellipsometry and density functional theory computation analysis. The normal spinel structure measured at room temperature in the range 100 cm–1–1200 cm–1. complex-valued dielectric function is determined from a wavenumber-by-wavenumber approach, which then analyzed four-parameter semi-quantum model approach augmented impurity contributions. We determine...

Abstract Polar dielectrics are key materials of interest for infrared (IR) nanophotonic applications due to their ability host phonon‐polaritons that allow low‐loss, subdiffractional control light. The properties limited by the characteristics optical phonons, which nominally fixed most “bulk” materials. Superlattices composed alternating atomically thin offer over crystal anisotropy through changes in composition, phonon confinement, and emergence new modes. In particular, modified phonons...

We demonstrate a unique class of advanced materials - quantum composites based on polymers with fillers comprised van der Waals material that reveals multiple charge-density-wave condensate phases. Materials exhibit phenomena are typically crystalline, pure, and have few defects because disorder destroys the coherence electrons phonons, leading to collapses states. succeeded in preserving macroscopic phases filler particles after composite processing steps. The prepared manifest strong even...

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 1 THz was carried out on bulk crystals along different orientations. Principal directions for crystallographic axes c, and b, reciprocal lattice direction a*. No significant dispersion real part dielectric observed measured range. Our results are excellent...

The bowing of the energy three lowest band-to-band transitions in $\beta$-(Al$_{x}$Ga$_{1-x}$)$_2$O$_3$ alloys was resolved using a combined density functional theory (DFT) and generalized spectroscopic ellipsometry (GSE) approach. DFT calculations electronic band structure both, $\beta$-Ga$_2$O$_3$ $\theta$-Al$_2$O$_3$, allow extracting linear portion shift alloys, provide method for quantifying role coherent strain present thin films on (010) substrates. energies were obtained...