Annealing studies on Pd/n-GaAs Schottky diodes
Pd/n-GaAs Schottky diodes were fabricated by using either spin-on or evaporated Pd sources. Initial electrical characteristics of both types of Schottky diode revealed little difference in their respective diode parameters. Capacitance-voltage (C-V) measurements gave a barrier height of 0.85+or-0.01 eV for spin-on Pd diodes as compared with a barrier height of 0.88+or-0.01 eV for evaporated Pd devices. The ideality factor for both diodes was found to be close to unity. Elevated temperature aging studies at temperatures up to 200 degrees C for 1000 h, produced little or no change in diode parameters. On the other hand annealing at 250 degrees C for times up to 1000 h resulted in a gradual degradation of diode parameters. This degradation in diode parameters was significantly more rapid during a 400 degrees C anneal. Using a failure criterion of a sixfold increase in reverse saturation current Jsriv, an Arrhenius plot was constructed by plotting log time to failure versus 1000/T, where T is the aging temperature. The resulting plots were linear indicating a single failure mechanism being dominant at all temperatures. The room temperature (300 K) median life, for a sixfold increase in Jsriv, of Pd/n-GaAs Schottky diodes from spin-on and evaporated Pd sources was found to be 105 h and 4*103 h, respectively.