A comparative study of optical property on unintentionally doped and Sn-Doped β-Ga2O3 crystals by EFG method with a cylindrical Ir die

• A comparative study of optical property on unintentionally doped and Sn-doped β -Ga 2 O 3 crystals. • The strong anisotropy in Raman peak and intensity of β -Ga 2 O 3 between three different planes and in-plane. • The strong anisotropy in optical transmittance, bandgap values, surface barrier height, luminescence centers and level of electron ionization. In this work, we carried out a comparative study of optical property on unintentionally doped and Sn-doped β -Ga 2 O 3 crystals by edge-defined film-fed growth (EFG) method with a cylindrical iridium (Ir) die. The non-polarized Raman spectra showed the anisotropy in Raman peak position and intensity for three different planes (i.e., (100), (010) and (001)) of β -Ga 2 O 3 crystals, independent of the Sn dopant. A difference in the Raman spectra between the unintentionally doped and Sn-doped β -Ga 2 O 3 crystals was observed in the (001) plane. The strong in-plane anisotropy of the monoclinic β -Ga 2 O 3 crystal related to the crystallographic orientation was demonstrated by the angle-resolved polarized Raman spectroscopy. The Sn dopant cannot change the optical transmittance and bandgap values of the unintentionally doped and Sn-doped β -Ga 2 O 3 crystals with the (100), (010) and (001) orientations. However, the Sn-doped β -Ga 2 O 3 crystal with the (010) orientation showed the higher valence band maximum and lower surface barrier height values. The X-ray photoelectron spectroscopy of the unintentionally doped and Sn-doped β -Ga 2 O 3 crystals with the (010) orientation was also measured, which showed no obvious difference. The different luminescence centers and level of electron ionization of the unintentionally doped and Sn-doped β -Ga 2 O 3 crystals were observed by the cathodoluminescence spectroscopy and electron paramagnetic resonance, respectively. Based on the comprehensive comparison, it can be concluded that the anisotropy in optical property of the unintentionally doped and Sn-doped β -Ga 2 O 3 crystals with (100), (010) and (001) orientations apparently exist.