Polarized UV–Visible Photoluminescence from Bulk β‐Ga2O3 Crystals

Herein, a study of photoluminescence (PL) of bulk β ‐Ga 2 O 3 crystals measured at different crystallographic directions is presented. The bulk β ‐Ga 2 O 3 crystals are grown using the optical floating zone method and cut to prepare three basic planes for optical investigations. The Ga 2 O 3 emits PL from red (1.7 eV) to near UV (3.5 eV). The maximum is at about 3 eV. It is shown that the excitation of Ga 2 O 3 depends on polarization: the lowest excitation energy 4.7 eV is observed for polarization along the b axis. The PL emission is clearly polarized, which can be used to build diodes emitting polarized light: polarized light‐emitting diodes. For example, the main emission from the (100) plane is polarized along [001] direction. Analysis of polarization and dynamics of PL shows that the main emission band is composed of a few spectrally overlapping luminescence bands. The bands are resolved thanks to different polarization and significantly different dynamics. The violet PL at about 3.0 eV has a lifetime τ = 0.6 μs and the blue PL at about 2.8 eV has τ of about 600 μs. Such long lifetimes are characteristic of deep centers, for example, the oxygen vacancy V O or the V Ga –Ga i –V Ga defect.