Annealing of intimate Au-GaAs Schottky barriers: Thick and ultrathin metal films

Using valence-band and core-level photoemission spectroscopy (PES) and electrical device measurements, the effects of annealing on Au:n-type (110) GaAs Schottky diodes fabricated in ultrahigh vacuum have been studied. Similiar trends in the annealing-induced changes in the barrier height of Au:n-type GaAs were found for 0.2 and 15 monolayer coverages as determined by PES and for thick film coverages (1000 Å) as determined by current-voltage (I-V) and capacitance-voltage (C-V) measurement techniques. In each case, the barrier height was found to be stable for temperatures between 30 and 200 °C and between 300 and 500 °C; while a gradual decrease in the barrier height was found for annealing temperatures of 200-300 °C. These changes are correlated with the formation of a Au-Ga rich layer at the interface during anneals at 200 to 300 °C. Leakage currents were found to dominate the I-V characteristics in the devices which were annealed above the Au-Ga eutectic temperature. These peripheral leakage currents were eliminated by mesa-etching the devices. This allowed more reliable barrier height determinations using device measurements for higher annealing temperatures than has been previously reported for the Au-GaAs system.