Crystal orientations of β‐Ga₂O₃ thin films formed on n‐plane sapphire substrates

Abstract

We have used X‐ray pole figure analysis to study crystal orientations of β‐Ga2O3 thin films deposited on (113) n‐plane sapphire substrates by gallium evaporation in oxygen plasma. The films were strongly (−201)‐oriented. However, the (−201) plane of β‐Ga2O3 on the (113) n‐plane sapphire was inclined along the (110) a‐plane. Crystals of (−201)‐oriented β‐Ga2O3 exhibit a threefold symmetry in which the β‐Ga2O3 crystal is rotated by increments of 120° from the direction of the c‐axis on the a‐plane of sapphire. The crystal orientation of β‐Ga2O3 was explained by comparing oxygen atom arrangements on the β‐Ga2O3 plane in three different configurations and on the (113) n‐plane sapphire substrates.

Deep Ultraviolet Optical Anisotropy of β-Gallium Oxide Thin Films

“…The XRD observations in Figure support the hypothesis that the β-Ga 2 O 3 / r -cut sample has a larger mosaicity degree and the crystalline orientation of the grains are not aligned with the surface of the r -cut sapphire substrate. Instead, the ( true 2 ̅ 01) plane of β-Ga 2 O 3 are aligned with the (113) or (2 true 1 ̅ 3) plane of the r -cut sapphire substrate. − This corresponds to a 3-fold symmetry arrangement of the β-Ga 2 O 3 ( true 2 ̅ 01) plane rotated at every 120° angle on two of the (113) or (2 true 1 ̅ 3) planes of the sapphire substrate, which are inclined by ±27° from the r -cut plane . DUV reflectance and Raman mode anisotropy of the β-Ga 2 O 3 / r -cut shown in Figures and are due to the ( true 2 ̅ 01) β-Ga 2 O 3 crystal tilted arrangement with the (113) or (2 true 1 ̅ 3) sapphire substrate orientations. , On the other hand, the β-Ga 2 O 3 / c -cut crystalline orientation is aligned with the sapphire c -cut plane resulting in an isotropic DUV reflectance and Raman mode.…”

“…We determined the full width at half-maximum (fwhm) of the β-Ga 2 O 3 diffraction peaks at ( 02) and (402) as 0.206° and 0.884°, respectively, for the c -cut and r -cut samples. The wider diffraction pattern peaks of the β-Ga 2 O 3 / r -cut suggests the crystalline grains were arranged with a higher mosaicity, when compared to the c -cut, or the ( 02) direction of the β-Ga 2 O 3 crystal orientation does not align with the r -cut plane. − …”

“… 34 DUV reflectance and Raman mode anisotropy of the β-Ga 2 O 3 / r -cut shown in Figures 5 and 6 are due to the ( 01) β-Ga 2 O 3 crystal tilted arrangement with the (113) or (2 3) sapphire substrate orientations. 34 , 35 On the other hand, the β-Ga 2 O 3 / c -cut crystalline orientation is aligned with the sapphire c -cut plane resulting in an isotropic DUV reflectance and Raman mode.…”