MODULATED-BEAM STUDIES OF THE LAYER-BY-LAYER ETCHING OF GAAS(001) USING ASBR3 - IDENTIFICATION OF THE REACTION-MECHANISM

Modulated-beam mass spectroscopy (MBMS) has been used to study the rea ction mechanism of the layer-by-layer etching of GaAs(001) using AsBr3 under molecular beam epitaxy conditions. It is shown that GaBr is the main etching product and its ''delay'' time with respect to the incid ent AsBr3 flux exhibits a strong dependence on substrate temperature, changing from 12 ms in the reaction limited regime at 387 degrees C to less than 0.5 ms at 560 degrees C. Desorbing As-containing species ap pear to have very short surface lifetimes throughout the temperature r ange investigated and the additional As-2 flux supplied from a solid s ource has no effect on the etching rate. The results suggest a reactio n pathway where the rate limiting step is the formation or description of GaBr and not the decomposition of AsBr3.