Electronic properties and transformation kinetics of two prominent metastable defects introduced in GaAs during sputter deposition of Au Schottky contacts

Abstract

Au Schottky barrier contacts (SBDs) were DC sputter deposited on Si doped n-type GaAs at a power of 150 W. Deep-level transient spectroscopy (DLTS) and Laplace DLTS were used to characterize the sputter-induced defects near the surface of the GaAs. In this study, I-V and C-V measurements showed that the sputter deposited diodes had a significantly lower barrier height and a higher free carrier density. Using DLTS, it was found that this sample contained seven defects – three of them were metastable while one of the others was highly dopant dependent. The energy levels of these defects are Ec – 0.046 eV, Ec – 0.22 eV, Ec – 0.30 eV, Ec – 0.55 eV, Ec – 0.56 eV, Ec – 0.83 eV and Ec – 0.84 eV. The EL2 defect was not observed in the sputtered samples, but one of the sputter-induced defects emitted in the same range as the EL2, however, it had two components and their DLTS signatures (Ec – 0.83 eV and Ec – 0.84 eV) differed significantly from that of the EL2. By applying different bias conditions (−2 V and zero V) for annealing procedures, the metastable defects (Ec – 0.30 eV and Ec – 0.56 eV) were transformed into each other. The pre-factor obtained from transformation rate of Ec – 0.56 eV →Ec – 0.30 eV under reverse bias was 3 × 1015 s−1 which is related to free carrier emission.