Dissociative electron attachment of CH3Br on GaAs(110) by thermalized photoexcited substrate electrons

We have investigated the effect of laser irradiation on the terrace morphology of Br-covered GaAs ͑110͒. Layer-by-layer etching of GaAs ͑110͒ is demonstrated through laser-induced etching and atomic desorption. Nanosecond pulsed-laser irradiation ͑hϭ2.3 eV, pulse power ϳ35 mJ cm Ϫ2 ͒ of Br-GaAs ͑110͒ initially produces a high density of small, single-layer etch pits as Br is consumed. Continued laser irradiation causes Ga and As desorption from pit edges so that pits grow and thereby remove the remnant of the top GaAs layer. When there is Br on the surface, pit growth reflects the Br chemisorption structure ͑elongated along ͓001͔͒ but subsequent atom desorption favors growth along ͓110͔.