The anisotropic quasi-static permittivity of single-crystal <b>
                     <i>β</i>
                  </b>-Ga2O3 measured by terahertz spectroscopy

Gopalan, Prashanth; Knight, Sean; Chanana, Ashish; Stokey, Megan; Ranga, Praneeth; Scarpulla, Michael A.; Krishnamoorthy, Sriram; Darakchieva, Vanya; Galazka, Zbigniew; Irmscher, K.; Fiedler, Andreas; Blair, Steve; Schubert, Mathias; Sensale‐Rodriguez, Berardi

doi:10.1063/5.0031464

“…Such Fabry-Perot interference fringes increase sensitivity to the quasi-static DC permittivity, as demonstrated recently for β-Ga 2 O 3 . 73 Figure 8 depicts measured and bestmodel calculated THz Mueller matrix data measured at 50 • angle of incidence. The best-model calculated data were obtained without further parameter variations only using the static dielectric constant and the Drude model in Eq.…”

Section: Static and High Frequency Dielectric Constantsmentioning

confidence: 99%

Optical phonon modes, static and high-frequency dielectric constants, and effective electron mass parameter in cubic In2O3

Stokey

¹

,

Korlacki

²

,

Knight

³

et al. 2021

Journal of Applied Physics

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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 principle calculations. Dielectric function spectra measured on high quality, marginally electrically conductive melt grown single bulk crystals are obtained on a wavelength-by-wavelength (a.k.a. point-by-point) basis and by numerical reduction of a subtle free charge carrier Drude model contribution. A four-parameter semi-quantum model is applied to determine all sixteen pairs of infrared-active transverse and longitudinal optical phonon modes, including the high-frequency dielectric constant, ε ∞ = 4.05 ± 0.05. The Lyddane-Sachs-Teller relation then gives access to the static dielectric constant, ε DC = 10.55 ± 0.07. All experimental results are in excellent agreement with our density functional theory calculations and with previously reported values, where existent. We also perform optical Hall effect measurements and determine for the unintentionally doped n-type sample a free electron density of n = (2.81 ± 0.01) × 10 17 cm −3 , mobility of µ = (112 ± 3) cm 2 /(Vs), and an effective mass parameter of (0.208 ± 0.006)m e . Density and mobility parameters compare very well with results of electrical Hall effect measurements. Our effective mass parameter, which is measured independently of any other experimental technique, represents the bottom curvature of the Γ point in In 2 O 3 in agreement with previous extrapolations. We use terahertz spectroscopic ellipsometry to measure the quasistatic response of In 2 O 3 , and our model validates the static dielectric constant obtained from the Lyddane-Sachs-Teller relation.

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“…Such Fabry-Perot interference fringes increase sensitivity to the quasi-static DC permittivity, as demonstrated recently for β-Ga 2 O 3 . 71 Figure 10 depicts measured and bestmodel calculated THz Mueller matrix data measured at 50 • angle of incidence. The best-model calculated data were obtained without further parameter variations only using the static dielectric constant and the Drude model in Eq.…”

Section: Static and High Frequency Dielectric Constantsmentioning

confidence: 99%

Optical phonon modes, static and high frequency dielectric constants, and effective electron mass parameter in cubic In$_2$O$_3$

Stokey,

Korlacki,

Knight

et al. 2021

Preprint

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0

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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 principle calculations. Dielectric function spectra measured on high quality, marginally electrically conductive melt grown single bulk crystals are obtained on a wavelength-by-wavelength (a.k.a. point-by-point) basis and by numerical reduction of a subtle free charge carrier Drude model contribution. A four-parameter semi-quantum model is applied to determine all sixteen pairs of infrared-active transverse and longitudinal optical phonon modes, including the high-frequency dielectric constant, ε ∞ = 4.05 ± 0.05. The Lyddane-Sachs-Teller relation then gives access to the static dielectric constant, ε DC = 10.55 ± 0.07. All experimental results are in excellent agreement with our density functional theory calculations and with previously reported values, where existent. We also perform optical Hall effect measurements and determine for the unintentionally doped n-type sample a free electron density of n = (2.81 ± 0.01) × 10 17 cm −3 , mobility of µ = (112 ± 3) cm 2 /(Vs), and an effective mass parameter of (0.208 ± 0.006)m e . Density and mobility parameters compare very well with results of electrical Hall effect measurements. Our effective mass parameter, which is measured independently of any other experimental technique, represents the bottom curvature of the Γ point in In 2 O 3 in agreement with previous extrapolations. We use terahertz spectroscopic ellipsometry to measure the quasistatic response of In 2 O 3 , and our model validates the static dielectric constant obtained from the Lyddane-Sachs-Teller relation.

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“…The concept of generalized ellipsometry involved in THz-EPR-GSE provides promising prospects to characterize spin systems in highly anisotropic materials, for example in monoclinic symmetry β-Ga 2 O 3 . 41 We note that knowledge of the real and imaginary spectra of the spin transitions should be sufficient to calculate the volume density of spins, similar to the dipole density derived from the complex valued dielectric function. 1,21 We have demonstrated measurement of spin resonance at high magnetic fields using ellipsometry principles, and determined the complex valued magnetic polarizability of nitrogen doped 4H-SiC in the THz spectral range.…”

mentioning

confidence: 93%

Terahertz electron paramagnetic resonance generalized spectroscopic ellipsometry: The magnetic response of the nitrogen defect in 4H-SiC

Schubert,

Knight,

Richter

et al. 2022

Preprint

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We report on terahertz (THz) electron paramagnetic resonance generalized spectroscopic ellipsometry (THz-EPR-GSE). Measurements of the field and frequency dependencies of the magnetic response due to the spin transitions associated with the nitrogen defect in 4H-SiC are shown as an example. THz-EPR-GSE dispenses with the need of a cavity, permits independently scanning field and frequency parameters, and does not require field or frequency modulation. We investigate spin transitions of hexagonal (h) and cubic (k) coordinated nitrogen including coupling with its nuclear spin (I=1), and we propose a model approach for the magnetic susceptibility to account for the spin transitions. From the THz-EPR-GSE measurements we can fully determine the polarization properties of the spin transitions and we obtain g and hyperfine splitting parameters using magnetic field and frequency dependent Lorentzian oscillator lineshape functions. We propose frequency-scanning THz-EPR-GSE as a new and versatile method to study properties of spins in solid state materials.Electron paramagnetic resonance (EPR) is ubiquitous in science. 1 Traditional EPR instruments operate in the lower Gigahertz (GHz) range limited to one or a few frequencies only. 2 The possibility to access electron spin dynamics at much higher, i.e., Terahertz (THz) frequencies is attractive. Large energies permit better understanding of spin dynamics in single-molecule magnets, for example, 3,4 and allow investigation of systems with large zero-field splitting such as in transition metal complexes, 5,6 or in ultrawide-bandgap semiconductors, e.g., SiC 7-9 and group-III nitrides 10,11 for quantum technologies, or the recently emerging monoclinic gallium oxide for high voltage electronic applications. [12][13][14][15][16][17][18][19] To bring spin resonances into the THz range, superconducting magnets reaching large magnetic fields are necessary. The emergence of closed-cycle dry magnet systems and novel superconducting materials have made 20 T fieldflattened single-solenoid EPR magnets possible. 20 In the THz spectral range one can employ optical methods such as reflectance and transmittance measurements using free space plane wave propagation. Advantages of large-field frequency-scanning far-field THz EPR are manifold. The need for a fixed cavity and fixed frequency tied to the cavity is dispensed with. Furthermore, frequency scana) Electronic mail:

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The anisotropic quasi-static permittivity of single-crystal β -Ga2O3 measured by terahertz spectroscopy

Cited by 36 publications

References 33 publications

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

Optical phonon modes, static and high frequency dielectric constants, and effective electron mass parameter in cubic In$_2$O$_3$

Terahertz electron paramagnetic resonance generalized spectroscopic ellipsometry: The magnetic response of the nitrogen defect in 4H-SiC

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