Application of a slow positron beam to the PdGe ohmic contact on GaAs

Abstract

The depth distributions of Ga vacancies in the PdGe ohmic contact on GaAs were studied by a slow positron beam technique. The results were compared with the electrical properties, to interpret the mechanisms on both the ohmic contact formation and the degradation at the PdGe/GaAs interface. The magnitude of the S parameter, reflecting the Ga vacancy concentration, at the near-interface GaAs region increases during the PdGe ohmic contact formation on GaAs. This is due to the creation of the n(+)-GaAs interfacial layer below the contact. The S parameter in the interfacial layer increases with the annealing temperature, which indicates the elevation of the Ga vacancy concentration. The Ga vacancies reduce the electron concentration? resulting in the degradation of the contact resistivity.