Theoretical and experimental investigation of optical absorption anisotropy in beta-Ga2O3

F. Ricci;F. Boschi;A. Baraldi;FILIPPETTI, ALESSIO;M. Higashiwaki;A. Kuramata;FIORENTINI, VINCENZO;R. Fornari

2016-01-01

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Abstract

The question of optical bandgap anisotropy in the monoclinic semiconductor β-Ga2O3 was revisited by combining accurate optical absorption measurements with theoretical analysis, performed using different advanced computation methods. As expected, the bandgap edge of bulk β-Ga2O3 was found to be a function of light polarization and crystal orientation, with the lowest onset occurring at polarization in the ac crystal plane around 4.5–4.6 eV; polarization along b unambiguously shifts the onset up by 0.2 eV. The theoretical analysis clearly indicates that the shift in the b onset is due to a suppression of the transition matrix elements of the three top valence bands at Γ point.