Photodegradation of Si-doped GaAs Nanowire

Researching optical effects in nanowires (NWs) may requires high pump intensity that under ambient conditions can degrade NWs due to thermal oxidation. In this work we investigated the photodegradation of a single Si-doped GaAs NW by laser heating in air. To understand the changes occurred on the NW we carried out scanning electron microscopy (SEM), and energy dispersive X-ray (EDS), micro-Raman (μ-RS), micro-photoluminescence (μ-PL) spectroscopies in laser damaged regions as well as in non-affected ones. From Stokes and anti-Stokes peaks we estimated that the oxidation process starts at 661 K, resulting in two new modes at 200 and 259 cm^-1. SEM and EDS showed a significant loss of As in the oxidized regions, but no erosion of the NW. μ-PL showed the near-band-edge emission of GaAs along the NW, as well as a new emission band at 755 nm corresponding to polycrystalline β-Ga₂O₃ formation. Our results also indicate that neither amorphous As, nor crystalline As, were deposited at the surface of the NW. Combining different experimental techniques, this study showed the formation of polycrystalline β-Ga₂O₃ by oxidation of the NW surface and the limits to perform spectroscopic investigations on individual GaAs NWs under ambient conditions.