The distribution of Schottky barrier heights over the contact area in Au/III-V semiconductor (GaAs, InP, Al x Ga 1−x As, In x Ga 1−x As) diodes was determined using ballistic electron emission microscopy. Samples which received a chemical pretreatment in aqueous HF or HCl solutions showed changes in the barrier height distribution. In some cases, short rinses in deionized water could remove these effects. Additional XPS measurements and our former work on Si enabled us to propose a model wherein negatively charged species containing F or Cl at the interface are assumed to be responsible for these changes in barrier height distribution. However, in some cases, these effects were shadowed by more drastic influences due to the chemical processing such as changes in the stoichiometry of the surface region.

Ballistic electron emission microscopy (BEEM) has been applied to determine the barrier height change of contacts in which the GaAs substrate was dry etched by using SiCl 4 . The distribution of barrier heights over the contact area could be determined. It was found that dry etching introduced a second Gaussian distribution, with lower mean barrier height, next to the Gaussian distribution already found to be present in wet etched reference samples. This additional distribution occurred over the main part of the contact area. A model is proposed based on a change of the stoichiometry of the surface region produced by the reactive ion etching.

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