XPS analysis of wet chemical etching of GaAs(110) by Br-2-H2O: comparison of emersion and model experiments

We have applied photoelectron spectroscopy to investigate the surface compo sition after different surface treatments involving Br-2-H2O mixtures in or der to study wet chemical etching. Emersion experiments from Br-2.H2O solut ion are compared with model experiments, in which Br-2-H2O adsorbate and co adsorbate mixtures react with clean GaAs(110) surfaces. Our results indicat e that Ga- and As-bromides formed initially are hydrolyzed to form the resp ective oxides. Without addition of Br-2, only slight oxidation of the surfa ce takes place, There is an enrichment of Ga due to loss of As both in adso rption as well as in emersion experiments. Since in emersion experiments on ly a final situation is analyzed, the relative influence of surface reactiv ity and subsequent solvation effects cannot be distinguished easily, while model experiments give clear information on reaction products formed interm ediately. However, model experiments differ in environment and temperature from the real solid-liquid interface. The presented results demonstrate tha t a combination of emersion and model experiments provide valuable insight into the mechanism of wet chemical etching on a microscopic level. (C) 2000 Elsevier Science Ltd. All rights reserved,