Damage-free separation of GaN thin films from sapphire substrates

Gallium nitride thin films grown on sapphire substrates were successfully separated and transferred onto Si substrates using single 38 ns KrF excimer laser pulses directed through the transparent substrate at fluences in the range of 400–600 mJ/cm${}^2$ . The absorption of the 248 nm radiation by the GaN at the interface induces rapid thermal decomposition of the interfacial layer, yielding metallic Ga and N${}_2$ gas. The substrate is easily removed by heating above the Ga melting point of $\text{30\hspace{0.17em}°}$ C. Scanning electron microscopy and x-ray diffraction of the GaN films before and after lift-off demonstrate that the structural quality of the GaN films is not altered by the separation and transfer process.