Laser-induced interaction of ammonia with GaAs(100). I. Dissociation and nitridation

UV laser irradiation of ammonia adsorbed on GaAs(100) leads to molecular desorption and dissociation. A nitride passivation layer can be formed on the GaAs surface at 100 K by simultaneous exposure to ammonia and uv photons in a UHV environment. The nitride layer consists of a mixture of Ga and As nitrides. While the dominating GaN surface species is thermally stable, AsN desorbs below 800 K. Surface NH2 is identified as an intermediate. The implication of this study for selective area passivation and GaN growth is discussed.