Formation of As2O3 during anodic dissolution of GaAs

The formation of As2O3 particles on GaAs surfaces, which have been anodically polarized at potentials <1 V versus SCE, has been studied using SEM, EDX, AES and XPS. Selective dissolution of GaAs occurs resulting in the formation of an As-rich surface layer. The As layer agglomerates and oxidizes on exposure to air forming As2O3 particles. The particle formation is dependent on test conditions, with p-GaAs forming As2O3 in both dark and daylight conditions; As2O3 only forms on n-GaAs when polarized in daylight. Polarization at corrosion potentials does not lead to particle formation, as GaAs dissolution rates are too low for surface enrichment of As.