On the effects of air-exposure-time and time-dependency of Pb/p-Si Schottky diodes

The effects of air-exposure-time and time-dependency (ageing) on the Pb/p-Si Schottky diodes have been investigated by room temperature I-V and C-V measurements. The barrier height (BH) values between I-V and C-V measurements of the air-exposed samples have been found to be higher than those of the reference diode, and associated with the passivation of the intrinsic surface states on the cleaned Si surface. The ideality factor and the BH values of the air-exposed samples have reached to saturation after ten days air-exposure and the case has been interpreted as the saturation of the oxide layer thickness. The ageing has increased the ideality factors while decreasing the BHs of the samples with increasing ageing time. Both of the parameters have reached to the saturation at 720 h after metal deposition. The carrier concentrations of the air-exposed samples have been considerably lower than that of the reference diode and decreased with increasing exposure-time to air and ageing. This result has been attributed to the passivation of the acceptors by hydrogen atoms diffused into the semiconductor and so the surface Fermi level unpinning. The BH values determined from C-V measurements have reached to equilibrium BH values at 720 h after metal deposition as determined from I-V measurements.