Study of the properties of the surface of gallium arsenide by scanning atomic force microscopy

Using the method of atomic force microscopy, complex studies of the profile, potential distribution phi(x,y), and distributions of the phase contrast of the surface of n-GaAs subjected to various types of chemical treatment are carried out. The distribution of the potential and phase contrast at a microlevel, in general, correlates with the profile character. The surface treated in the solution H2SO4: H2O = 1: 10 is characterized by a high degree of nonuniformity with an average roughness of the main profile Delta h = 10 nm. A considerable part of the surface is covered by hills 20-60 nm in height and 100-500 nm in diameter forming a specific substructure, which correspond to potential jumps as large as 50-60 mV against a general background of 0.77-0.80 V. At a nanolevel, correlation between the profile and phase contrast is clearly pronounced, but no correlation is found between the profile and potential distribution. Treatment of the surface of n-GaAs in a concentrated aqueous NH4OH solution leads to a decrease in the value of phi(x,y) by similar to 0.2 V, and in its roughness by more than an order of magnitude (similar to 0.75 nm). The distribution of the profile and phase contrast over the surface is close to the ideal Gaussian distribution for relatively small areas of the surface (200 x 200 nm(2)). As the area increases, deviation from the Gaussian distribution becomes substantial because of smooth variation in the potential over the contact area. Conservation of the Gaussian character of the surface profile and a simultaneous rise in the average level of the roughness with an increase in the analyzed area indicates the fractal mechanism of formation of the surface profile.