Raman spectroscopy study on free-standing GaN separated from sapphire substrates by 532nm Nd:YAG laser lift-off

摘要

Gallium nitride (GaN) thin films grown on sapphire substrates were successfully lifted onto silicon wafer using Laser Lift-off (LLO) processinduced by 532nm, Nd:YAG pulsed laser. Although the photon energy (2.33eV) is much lower than the band gap of hexagonal GaN (3.41eV), can free-carriers absorption can heat up and consequently causes detachment of the GaN film from the sapphire substrate. Raman measurement conducted before and after LLO showed that the surface structure of the lifted GaN changed from hexagonal to cubic structure.