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

• DOI: 10.1016/j.diamond.2004.02.007
• Publication Date: 2004-04-17T21:45:43Z
• Authors: A. Venter; M.E. Samiji; A.W.R. Leitch
• Keywords: Passivation; Surface States

Abstract 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.