ELECTRICAL CHARACTERIZATION OF SPUTTER-DEPOSITION-INDUCED DEFECTS IN EPITAXIALLY GROWN N-GAAS LAYERS

Sputter deposition of metal Schottky contacts on semiconductors creates damage at and below the surface, often resulting in inferior rectification properties. We have employed deep-level transient spectroscopy (DLTS) to characterize the defects introduced during sputter deposition of Al Schottky barrier diodes (SBDs) on epitaxially grown n-GaAs with free carrier densities ranging from 4 x 10(14) to 1 x 10(16) cm(-3). Six sputter-induced electron traps, Es1-Es6, were defected at energy levels of 0.04, 0.13, 0.20, 0.31, 0.53, and 0.54 eV respectively, below the conduction band. The DLTS 'signatures' of Es1-Es4 were the same as those of defects introduced by-sub-threshold electron irradiation in the same GaAs. The Es5 at E(c)-0.53 eV could only be observed in Si-doped, but not in undoped GaAs, suggesting that it may be a complex involving Si. The concentrations of these defects decreased away from the interface to a depth that increased with decreasing GaAs free carrier density.