CL study of blue and UV emissions in ß-Ga_2O_3 nanowires grown by thermal evaporation of GaN

Abstract

We report a cathodoluminescence (CL) study of ß-Ga_2O_3 nanowires grown by thermal evaporation of GaN on Si(100) and Au/Si(00) substrates. Condensation and subsequent oxidation of metallic Ga is suggested as the growth mechanism of ß-Ga_2O_3 nanowires. The ß-Ga_2O_3 nanowires grown on Si(100) show multiple bends or undulations, together with a strong UV emission at 3.31 eV and a weak blue emission centered at 2.8 eV as a band component. The ß-Ga_2O_3 nanowires grown on Au/Si(100) substrates recorded a lower CL intensity of a well-defined blue emission of 2.8 eV. A thermal treatment on these samples produced an increase of the UV emission and quenching of the blue band. Thermal annealing of oxygen vacancies is proposed as the responsible mechanism for the observed behavior of these samples.