Anisotropy and In-Plane Polarization of Low-Symmetrical β-Ga2O3 Single Crystal in the Deep Ultraviolet Band

Abstract As a deep ultraviolet transparent conducting semiconductor, β-Ga2O3 has been actively studied for short wavelength optical and optoelectronic applications. This study investigated the anisotropy of optical properties, valence band structures, and the in-plane angle-resolved transmittance spectra of the three main crystal planes. The optical bandgaps of unintentionally doped β-Ga2O3 (100), (010), and (001) planes were 4.70, 4.55, and 4.70 eV, respectively. The valence band maximum of the (100), (010), and (001) planes obtained by VB-XPS were 3.4, 3.3, and 3.4 eV, respectively. A 0.05 eV larger surface bending band was found in the (100) and (001) planes than in the (010) plane. The transmitted intensity was established as a function of the in-plane polarization angles. The polarized optical bandgaps of E//a, E//b, and E//c were fit to 4.58, 4.73, and 4.48 eV, respectively, indicating that β-Ga2O3 can be used in polarization filtering and spectrally selective photodetectors in the UVC band, which was also demonstrated using two vertically stacked (100) single crystal wafers.