Effect of gamma-irradiation on structural, morphological, and optical properties of β-Ga2O3 single crystals

Gallium oxide (beta-Ga2O3) single crystals were grown using the optical floating zone (OFZ) technique. Compressed dry air was used as growth atmosphere. Several wafers of 1 mm thickness and 9 mm diameter were prepared from the as-grown beta-Ga2O3 single crystal. The wafers were irradiated with two different doses (50 and 75 kGy) of cobalt-60 source for gamma radiation and their properties were analyzed before and after irradiation. The structural variations were analyzed utilizing powder XRD and Raman spectroscopy. The results confirm the (010) orientation for the beta-Ga2O3 and the irradiated wafers. In addition, it reveals that the point defects cause lattice distortion and reduce the intensity of the active modes after irradiation. The impact of irradiation on the surface morphology of beta-Ga2O3 wafers such as nanometer-sized grooves were observed. AFM analysis indicates that the roughness value was enhanced from 1.22 to 8-10 nm for the irradiated wafers. The optical properties were analyzed using UV-Vis spectroscopy and photoluminescence measurements. The optical absorption in the visible range was altered after gamma irradiation. Optical bandgap energy was reduced to 4.04 eV for irradiated wafers. In photoluminescence, the blue emission decreases in intensity and shifts to the visible region due to gamma-ray-induced defects. The results reveal the potential application of as-grown beta-Ga2O3 in harsh environments.