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/cm(2)). Laser treatment was achieved in two experimental set up for complementary characterizatio n of the surface state: first mass spectrometry allowed us to follow d esorbed NHx species during the laser treatment and in a second step Ga N+ could be identified as an evidence of N fixation using laser desorp tion mass spectrometry of the treated surface. On a second experimenta l system, Auger in-situ studies showed preferential N adsorption on th e irradiated surface. Both characterization modes give evidence of flu ence 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).