Laser nano-soldering of ZnO nanowires and GaN thin film for fabrication of Hetero p-n junction

We have investigated the laser nano soldering between ZnO nanowires and the p-type GaN thin film for the realization of the hetero p-n junction with low thermal loading. When the ZnO nanowires were irradiated with 355 nm laser beam at a fluence of 0.25 J/cm², only a tip of the nanowires was melted due to the field enhancement effect near the tip of the nanowires, and a small bead with a diameter of 40 nm was formed at the tip of each nanowires. This phenomenon was applied to solder the junction between the ZnO nanowires and a p-type GaN thin film, by irradiating the junction through the GaN film with 375 nm laser beam which is transparent for the p-type GaN thin film but opaque for the ZnO nano-wires. As a result, the improvements of the I-V characteristics of the junction and the increment of the UV electro-luminescence were clearly observed, demonstrating the effectiveness of the nano soldering in fabrication of the hetero p-n junction between the ZnO nanowires and the GaN thin film.