Current Density-Anodic Potential Curves of Single Crystal GaAs at Low Currents in KOH

Abstract

Single p‐type, crystals of high purity, Zn doped, were used to determine whether or not the inverse octahedral {111} faces show potential differences and various rates of anodic dissolution. The Ga{III}, As{III}, {110}, and {100} faces, were polished, etched, and etch‐polished with concentrated , and immersed in . The Ga{III} faces were found to be the most noble with respect to rest and anodic dissolution potentials. The potential difference between the inverse {111} faces was as large as 0.14v for the rest and 0.123v for the dissolution potentials. The 4 anodic polarization curves gave nearly parallel Tafel lines, with a slope of 66.0 ± 1 mv/log i, up to current densities of 0.5 ma/cm². The rate of anodic dissolution of the As{III} faces was 69 X as high as the inverse Ga{III}. The activation energies of dissolution of all 4 faces were equal within experimental limits: 16.7 ± 0.7 kcal mole"⁻¹. It is concluded that the slow step in the dissolution of is a one electron discharge with subsequent steps leading to the formation of to provide a protective coating not readily soluble in . From this point of view all observed phenomena can be explained in a qualitative manner.