OBSERVATION OF HCL- AND HF-TREATED GAAS-SURFACES BY MEASURING CONTACT ANGLES OF WATER DROPLETS

A GaAs surface chemically treated with hydrochloric acid (HCl) or hydrofluoric acid (HF) has been characterized by measurements of the contact angle between the surface and a water droplet on it in air. The contact angle measured from the GaAs samples dipped into water shows the formation of a thin surface layer on the GaAs surface and the subsequent removal of the layer upon chemical treatment with HCl or HF solution. Annealing in nitrogen atmosphere is shown to be effective in stabilizing the surface against water.