Effect of Cr3+ ions on optical properties in β-Ga2O3 semiconductor

Cr-doping effects on optical properties of beta-Ga2O3 have been studied in single-crystalline samples, grown by floating-zone method. The photoluminescence, which is observed as an intense and broad peak in nominally pure beta-Ga2O3, is found be abruptly suppressed by Cr-doping. This suppression demonstrates that a small amount of Cr3+ ions acts as non-radiative centers for photo-excited carriers. In Cr-doped beta-Ga2O3 the residual photoluminescence shows UV and green emissions, peaking at about 3.3 eV and 2.4 eV, respectively. The photoluminescence excitation spectrum of the UV peak has a polarization-dependent maximum at the fundamental absorption edge that is arising from the band-to-band excitations. Therefore, the radiative decay channels for photo-excited carriers partly survive in Cr-doped beta-Ga2O3. We have also found a Cr-induced absorption band located just below the fundamental absorption edge. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim