Anisotropic Optical Properties of Metastable 
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Kracht, M.; Karg, Alexander; Feneberg, Martin; Bläsing, J.; Schörmann, Jörg; Goldhahn, R.; Eickhoff, Martin

doi:10.1103/physrevapplied.10.024047

Cited by 53 publications

(40 citation statements)

References 29 publications

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“…81 Nonetheless, the deposition of a Nd-doped a-Ga 2 O 3 layer as thick as 100 nm has also been reported, 83 suggesting that the presence of a dopant could affect the critical thickness of the layer on this orientation. Nonetheless, the thickest a-Ga 2 O 3 films were obtained on r-plane sapphire: 82 in this case a phase change to b-Ga 2 O 3 was recorded after about 200 nm of a-Ga 2 O 3 , due to the formation of large exposed c-facets which favour subsequent monoclinic phase nucleation. Being the formation of facets also related to the chemical potential during the thin film deposition, 94 we can argue that in the case of a-Ga 2 O 3 layers on r-plane sapphire substrates the thickness limitation for the obtainment of phase-pure layers could be overcome by properly tuning the Ga-to-O flux ratio.…”

Section: Substrate and Lattice Matchmentioning

confidence: 93%

“…In the case of a-Ga 2 O 3 the deposition temperature with MBE (no catalyst employed) has been so far limited to 500 1C r T g r 640 1C. [81][82][83] 2.3. Growth rate HVPE, MOVPE and mist-CVD all allow for comparable Ga 2 O 3 growth rates of about 500-1000 nm h À1 .…”

Section: Temperaturementioning

confidence: 99%

“…26 One possible explanation relies on the formation of wide facets [i.e., different surfaces not parallel to the (% 201) one] during MBE (% 201)-homoepitaxy, 12,13 which could favour the stabilization of the monoclinic polymorph, similarly to what has been previously discussed in the case of a-Ga 2 O 3 on r-plane sapphire substrates. 82 An interesting contribution about the role of the substrate in the nucleation of the a or e phase is given in ref. 90 and 96, using HVPE to grow Ga 2 O 3 on column-patterned sapphire.…”

Section: Substrate and Lattice Matchmentioning

confidence: 99%

“…12,97 Differently from the e-phase, the stability of a-Ga 2 O 3 layers is apparently only weakly affected by different oxygen-to-metal flux ratios, as shown for heteroepitaxial growth by MBE on r-plane sapphire substrates. 82…”

Section: Pressurementioning

confidence: 99%

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Ga₂O₃polymorphs: tailoring the epitaxial growth conditions

et al. 2020

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Section: Substrate and Lattice Matchmentioning

confidence: 93%

Section: Temperaturementioning

confidence: 99%

Section: Substrate and Lattice Matchmentioning

confidence: 99%

Section: Pressurementioning

confidence: 99%

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Ga₂O₃polymorphs: tailoring the epitaxial growth conditions

et al. 2020

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“…It should be noted that α ‐Ga 2 O 3 might also be observed at the interface with sapphire . Phase stabilization of α ‐Ga 2 O 3 was observed on r ‐plane α ‐Al 2 O 3 in plasma‐assisted MBE up to a film thickness of around 200 nm . Thus, initially the resulting strain energy due to lattice mismatch shifts the thermodynamic equilibrium from the stable β ‐Ga 2 O 3 toward the metastable α‐modification .…”

Section: Resultsmentioning

confidence: 98%

Progress in Sputter Growth of β‐Ga₂O₃ by Applying Pulsed‐Mode Operation

Schurig

Michel

Beyer

et al. 2020

Physica Status Solidi (a)

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β‐Ga2O3 thin films are deposited by pulsed radio‐frequency (RF) magnetron sputtering on c‐sapphire substrates, using a stoichiometric Ga2O3 target and a constant gas flux of an argon–oxygen mixture. Pulsed sputtering offers a way to overcome the restrictions of conventional sputtering. The parameters RF power and pulse duty cycle (PDC) are varied systematically to optimize the synthesis of Ga2O3 thin films. Subsequently, the resulting as‐deposited (AD) Ga2O3 layers are analyzed in terms of structural and optical properties and the results are compared with those on the samples treated by postdeposition rapid thermal annealing. Based on this analysis, the process parameters are evaluated in terms of β‐Ga2O3 formation. Postdeposition temperature treatments are found to yield a better crystal quality. However, a strong interdiffusion with the Al2O3 substrate is observed. The optical bandgap of the sputtered thin films is found to be quite independent of the RF sputtering power but to depend strongly on the PDC used, whereas the layer thickness rather strongly increases with both of those growth parameters. These evolutions are assigned to changes in the energy and ionic species of the plasma. Traces of GaOx‐related phases in addition to β‐Ga2O3 are found in the interphase between the growing thin films and the underlying substrate.

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Electromagnetic Waves in Crystals: The Presence of Exceptional Points

Sturm

2024

Advanced Photonics Research

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Although the investigation of the propagation of electromagnetic waves in crystals dates back to the 19th century, the presence of singular optic axes in optically anisotropic materials has not been fully explored until now. Along such an axis, either a left or a right circular polarized wave can propagate without changing its polarization state. More generally, these singular optic axes belong to exceptional points (EPs) in the momentum space and correspond to a simultaneous degeneration of the eigenmodes and their propagation properties. Herein, a comprehensive discussion on EPs in optically anisotropic materials, their occurrence, and properties as well as the properties of the electromagnetic waves propagating along such EPs is presented. The presence of such EPs, their spatial and spectral distribution in bulk, and semi‐infinite and finite crystals are discussed. It is shown that the presence of interfaces has a strong impact on the presence of the EPs and their spatial distribution. At an EP, the propagation of an arbitrarily polarized wave cannot be described by a superposition of two eigenmodes, as typically described in textbooks. This leads to singularities if the reflection and transmission coefficients have to be calculated. Here, two approaches are presented to overcome these limitations.

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Anisotropic Optical Properties of Metastable (011¯2)α−Ga2O3

Cited by 53 publications

References 29 publications

Ga₂O₃polymorphs: tailoring the epitaxial growth conditions

Ga₂O₃polymorphs: tailoring the epitaxial growth conditions

Progress in Sputter Growth of β‐Ga₂O₃ by Applying Pulsed‐Mode Operation

Electromagnetic Waves in Crystals: The Presence of Exceptional Points

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Anisotropic Optical Properties of Metastable (011¯2)α−Ga2O3

Cited by 53 publications

References 29 publications

Ga2O3polymorphs: tailoring the epitaxial growth conditions

Ga2O3polymorphs: tailoring the epitaxial growth conditions

Progress in Sputter Growth of β‐Ga2O3 by Applying Pulsed‐Mode Operation

Electromagnetic Waves in Crystals: The Presence of Exceptional Points

Contact Info

Product

Resources

About

Ga₂O₃polymorphs: tailoring the epitaxial growth conditions

Ga₂O₃polymorphs: tailoring the epitaxial growth conditions

Progress in Sputter Growth of β‐Ga₂O₃ by Applying Pulsed‐Mode Operation