Laser induced nitridation of Ga on GaAs surfaces

摘要

We have studied the reactivity of NH_3 on GaAs (100) surface irradiated by UV laser beam at low fluences (<50 mJ/cm~2). Laser treatment was achieved in two experimental set up for complementary characterization of the surface state: first mass spectrometry allowed us to follow desorbed NH_x 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/cm~2.