Influence of Current Stressing on the Structure of Ag Contacts to GaAs

摘要

The stability of Ag Schottky contacts on GaAs after voltage and current stressing has been investigated. The barrier height and its stability against voltage and current stressing were found to depend on the diode fabrication method (metal deposition onto either air-exposed or ultra-high vacuum cleaved (uhv) substrates). The barrier height of Ag diodes formed on air-exposed surfaces is 0.96 eV, and a significant decrease of 70 MeV was found upon exposure to voltage and current stressing. In contrast, the barrier height of Ag diode formed on uhv cleaved samples is 0.89 eV, and no significant change was found upon exposure to stressing. The structure of the contacts was studied by transmission electron microscopy. Ag deposited on uhv cleaved substrates shows an epitaxial relationship to GaAs and atomically flat interfaces. Exposure to air before the metal deposition led to nonuniform reactions and compound formation at the interface as compared to uhv samples. After current stressing, void formation and electromigration of Ag were observed in the air-exposed contacts. Ag contacts formed on uhv-cleaved GaAs(110) were stable during current stressing. 7 refs., 5 figs. (ERA citation 13:024926)