Non-linear photo-induced desorption of GaP

Abstract Laser-induced desorption of P from GaP at various photon energies near the absorption edge has been measured. The desorption yield is found to start increasing above a certain threshold laser fluence, of which the dependence on the photon energy exhibits a sharp dip near the indirect band gap besides a gradually decreasing component from the indirect band gap to the direct band gap energy. The sharp dip is ascribed to desorption induced by dense excitation of the surface states.