Atomic force microscopy study of the potential distribution over a locally metallized n-GaAs surface

Investigations of the potential of the free surface of gallium arsenide and of the surface coated (locally or entirely) by thin layers of gold or platinum have been carried out using atomic force microscopy in the Kelvin mode. The results obtained show that the potential measured in the metal-probe system corresponds as a whole to its contact potential difference (CPD). CPD values measured for the gallium arsenide-probe system depend on the type of processing that may be related to the influence of the processing on the electron affinity of a semiconductor. The lateral size effect consisting in the presence of a significant (about 10 μm) transition zone (aureole) between the metal contact and the GaAs free surface has been found. In this region the potential varies gradually between values of the potential of the metal contact and the free surface of the semiconductor. The potential of a contact depends on its dimensions (diameter and thickness) and on the substrate material’s (GaAs) properties.