Aging of Schottky diodes formed on air-exposed and atomically clean GaAs surfaces: An electrical study

Abstract

In this report we show that the application of a large voltage and current stress can significantly change the barrier height of a given metal (Ag,Al,Au,Pd,Cr)/GaAs(110) contact. These changes of barrier height depend on the metal used, the method of fabrication of the diode (air exposed or UHV cleaved), and the intensity and direction of the potential and current during the electrical aging. In particular, the air-exposed Ag diodes exhibit the largest change in the barrier height (∼85 meV) upon aging, while the UHV-cleaved Ag diodes do not exhibit a significant change. In the case of Au, both UHV-cleaved and air-exposed diodes show a small change (∼20 meV). The barrier heights of Pd, Al, and Cr air-exposed diodes do not exhibit an appreciable change upon aging (i.e., <10 meV). The changes in barrier height are found to have a very consistent and characteristic logarithmic dependence upon time. Once the electrical aging is stopped, the barrier height is found to recover to near the unaged value. The long time constant of the aging process, the ability of the barrier height to recover after aging, the long time constant of the recovery process, and the acceleration of the recovery process by illumination suggest that the changes in the barrier height which occur upon electrical aging are due to the creation and/or annihilation of deep level traps near the interface. We also report a systematic study of a comparison of barrier height determinations for Ag, Al, Au, Cr, and Pd diodes formed on air-exposed and UHV-cleaved GaAs(110) surfaces.