The Spatial Correlation and Anisotropy of β-(AlxGa1−x)2O3 Single Crystal

Abstract

The long-range crystallographic order and anisotropy in β-(AlxGa1−x)2O3 (x = 0.0, 0.06, 0.11, 0.17, 0.26) crystals, prepared by optical floating zone method with different Al composition, is systematically studied by spatial correlation model and using an angle-resolved polarized Raman spectroscopy. Alloying with aluminum is seen as causing Raman peaks to blue shift while their full widths at half maxima broadened. As x increased, the correlation length (CL) of the Raman modes decreased. By changing x, the CL is more strongly affected for low-frequency phonons than the modes in the high-frequency region. For each Raman mode, the CL is decreased by increasing temperature. The results of angle-resolved polarized Raman spectroscopy have revealed that the intensities of β-(AlxGa1−x)2O3 peaks are highly polarization dependent, with significant effects on the anisotropy with alloying. As the Al composition increased, the anisotropy of Raman tensor elements was enhanced for the two strongest phonon modes in the low-frequency range, while the anisotropy of the sharpest Raman phonon modes in the high-frequency region decreased. Our comprehensive study has provided meaningful results for comprehending the long-range orderliness and anisotropy in technologically important β-(AlxGa1−x)2O3 crystals.

Influence of framework disordering on the luminescence performance of Cr3+-doped near-infrared phosphors: a case study of A3B6O14-type hosts

“…The spectra exhibited complicated Raman scattering peaks due to the vibration of Na–O, Ca–O, Ga–O and Ge–O bonds. It is evident that the peak at 806.58 cm −1 , attributed to the stretching vibration of (Ga,Ge)–O bonds in [(Ga,Ge)O 4 ] tetrahedra, 23,24 shifted to 861.42 cm −1 when transitioning from Ca 3 Ga 2 Ge 4 O 14 to Na 2 CaGe 6 O 14 . The substitution of larger Ga 3+ ( R Ga(III),4CN = 0.47 Å) by smaller Ge 4+ ( R Ge(IV),4CN = 0.39 Å) induced shorter (Ga,Ge)–O bonds, 13 enhancing the bonding strength and increasing the scattering frequency, 25 in line with the Raman shift.…”