Laser induced nitridation of Ga on GaAs surfaces

We have studied the reactivity of NH3 on GaAs (100) surface irradiated by UV laser beam at low fluences (< 50 mJ/cm2. Laser treatment was achieved in two experimental set up for complementary characterization of the surface state: first mass spectrometry allowed us to follow desorbed NHx species during the laser treatment and in a second step GaN+ could be identified as an evidence of N fixation using laser desorption mass spectrometry of the treated surface. On a second experimental system, Auger in-situ studies showed preferential N adsorption on the irradiated surface. Both characterization modes give evidence of fluence and laser shot number dependencies on laser treatment efficiency. At 280 nm the N fixation is maximum for laser fluence of about 25 mJ/cm2.