THE CONTINUING DRAMA OF THE SEMICONDUCTOR INTERFACE

Studies on III-V compound semiconductor surfaces and metal interfaces are discussed. For GaAs and InP surfaces aqueous photowashing or chalcogenide coatings can significantly reduce surface state densities. For metal interfaces experimental conditions have been found which lead to metal work function dominated Schottky barrier heights to GaAs. Finally, using special epilayer samples of GaAs, AlGaAs and InGaAs containing a significant excess of As, more has been learned about the origin of the invariance of the interface Fermi level (pinning) commonly observed at III-V semiconductor interfaces. The excess As can form either a high density of point defects or a dispersion of elemental As clusters depending on the post growth annealing conditions. It has been found that the pinning effects of point defects are qualitatively different from those due to the clusters of elemental As. Specifically, when the excess As is in the form of As precipitates, the As forms a Schottky barrier whose barrier height is well characterized by the parameters of As work function and semiconductor electron affinity.