Lattice parameters and Raman-active phonon modes of (InxGa1–x)2O3 for x < 0.4

Abstract

We present X-ray diffraction and Raman spectroscopy investigations of (InxGa1–x)2O3 thin films and bulk-like ceramics in dependence of their composition. The thin films grown by pulsed laser deposition have a continuous lateral composition spread allowing the determination of phonon mode properties and lattice parameters with high sensitivity to the composition from a single 2-in. wafer. In the regime of low indium concentration, the phonon energies depend linearly on the composition and show a good agreement between both sample types. We determined the slopes of these dependencies for eight different Raman modes. While the lattice parameters of the ceramics follow Vegard's rule, deviations are observed for the thin films. Further, we found indications of the high-pressure phase InGaO3 II in the thin films above a critical indium concentration, its value depending on the type of substrate.

Raman tensor elements of β-Ga2O3

“…The lattice parameter optimization with these parameters yields a 0  = 12.336 Å, b 0  = 3.078 Å, c 0  = 5.864 Å and β  = 103.89°. This slight overestimation of the lattice parameters with respect to experimental values151617 is expected for the B3LYP hybrid functional131418.…”

Dielectric function in the NIR-VUV spectral range of (InxGa1−x)2O3 thin films

“…In that composition range, we have found in the Raman data strong signatures of the highpressure rhombohedral InGaO 3 -II phase. 22 As mentioned above, from the structural point of view, this phase shows no similarity to rh-In 2 O 3 . [22][23][24][25] The electronic structure of InGaO 3 -II is not known so far, but it seems that the optical response and thus also the electronic structure of that phase should be similar to that of the rh-In 2 O 3 phase.…”

“…As also detailed in Ref. 22, the composition as a function of the position on the wafer and the structural properties of the thin films have been investigated by means of energy dispersive X-Ray analysis (EDX), X-Ray diffraction (XRD), and Raman spectroscopy. Figure 1 displays EDX line scans of the In concentration of the samples.…”

“…Ref. 22), no optical or band structure properties are available. It shall be mentioned that the two rhombohedral phases not only differ in stoichiometry, but are two different crystal structures with regard to yet known structural and phonon mode properties.…”

“…It shall be mentioned that the two rhombohedral phases not only differ in stoichiometry, but are two different crystal structures with regard to yet known structural and phonon mode properties. [22][23][24][25] The highest valence bands of b-Ga 2 O 3 consist mainly of O 2p orbitals, 2-4 which for bcc-and rh-In 2 O 3 are hybridized with In 4d (Refs. 5-7)/In 5p (Ref.…”