ARSENIC ADSORPTION ON GAAS(001)

A method for accurate determination of the arsenic coverage of reconst ructed (GaAs(001) surfaces prepared by molecular beam epitaxy (MBE) is presented. The time of gallium supply to the reconstructed surface un til a halo appears in the reflection high energy electron diffraction (RHEED) pattern is taken as measure for the arsenic coverage. (2 x 4), c(4 x 4), (2 x 3) and also intermediate GaAs(001) surface structures were investigated at a substrate temperature of 200-degrees-C. The RHE ED results were verified by high resolution scanning electron microsco py (HRSEM). Dependent on the surface reconstruction, arsenic coverages between 0.76 and 1.22 monolayer (ML) were observed. The relation betw een RHEED pattern and arsenic coverage is discussed quantitatively.