The effect of different treatments on fractal forms of gallium arsenide surface

The surface of epitaxial gallium arsenide (as-grown and subjected to standard chemical treatments for producing metal-GaAs electrical contacts) has been studied by atomic force microscopy. It was shown that the surface relief can be characterized by fractal relief in the local approximation. As-grown epitaxial n-GaAs layers have lower values of the mean relief irregularity and roughness and reveal high surface homogeneity. The most marked relief changes are observed due to plasmachemical deposition of silicon dioxide and its removal in a buffered etch and deionized water rinse. The following finishing treatments make the surface more smooth and homogeneous, especially in ammonia-water mixture, which gives almost an ideal (Gaussian) distribution of irregularities and phase contrast in most cases. The fractal dimensionality of the studied surfaces changes in the relatively narrow limits D _f = 2.5−2.8. The values of the local approximation limit L determining the boundary of the applicability of the fractal approach when describing the surfaces change from 0.039 to 10.99 μm depending on the kind of treatment.