Study of the laser lift-off technology of GaN films from sapphire substrates

Gallium Nitride films grown on sapphire substrates were successfully separated by laser radiation. The absorption of the 248 nm radiation by the GaN at the interface results in rapid thermal decomposition of the interfacial layer, yielding metallic Ga and N₂ gas. The substrate can be easily removed by heating above the Ga melting point of 30°C. Atomic force microscopy, X-ray diffraction and Photoluminescence of GaN before and after lift-off process have been performed, which demonstrated that the separation and transfer process do not alter the structural quality of the GaN films. And further discussions on the threshold energy and crack-free strategies of laser lift-off process have also been presented.