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

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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.

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