Formation of surface states during Schottky barrier fabrication on Al-doped p-type 6H-SiC

I-V measurements of an as-deposited Ru Schottky barrier diode (SBD) revealed a shift of -0.6 V in the minimum current. This shift is attributed to the presence of localized interface states that modifies the barrier height. Annealing as-deposited and plasma exposed Ru SBDs revealed that the off-set was temperature dependent, suggesting that appropriate selection of anneal temperature may result in reconstruction of the surface, consequently removing the surface states responsible for the distorted I-V response. The effect of hydrogen on the Schottky contact was investigated by exposing the metalized front surface of the SiC to a d.c. hydrogen plasma for 120 min. Capacitance-Voltage (C-V) depth profiles of the H-plasma exposed SBDs revealed a reduction in the near-surface free carrier concentration, suggesting passivation of the Al acceptors by hydrogen. This was confirmed by subsequent reactivation of the electrical activity of the Schottky contact through a series of isothermal reverse bias annealing experiments. (C) 2004 Elsevier B.V. All rights reserved.