Optical evidence of intrinsic quantum wells in the transparent conducting oxide β-Ga2O3

A peculiar peak structure is observed in the optical absorption edge of $\mathrm{\beta -}{\mathrm{Ga}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ at low temperature. These peaks appear in an energy range corresponding to the excitation of the acceptor defects. It is suggested that some of these acceptors be assembled in low dimensional clusters with size about 30–40 Å and forming potential wells with depth about 0.5 eV. The extra peaks are interpreted as transitions between the discrete energy levels of these potential wells and the conduction band.