Poster abstract

We report on the passivation by hydrogen and the subsequent thermal reactivation of the acceptors in Al-doped p-type 6H-SiC. In order to introduce hydrogen into the SiC, Schottky barriers were formed by evaporating a thin film of ruthenium through a contact mask. The Schottky barrier diodes were then exposed to a remote hydrogen plasma at 200C. Ru was chosen as the Schottky barrier metal for both its permeability to hydrogen as well as its thermal stability [1]. The Ru film also serves to protect the SiC surface from possible damage related to the plasma exposure. Capacitance-voltage measurements revealed that the near-surface free carrier concentration was reduced by at least an order of magnitude after the hydrogen plasma treatment.

The thermal stability of the Al-H complex in the hydrogenated SiC was investigated through a series of isothermal anneals at temperatures ranging from 200C to 275C, while applying a reverse bias to the Ru Schottky barrier. The electric field associated with the applied reverse bias caused the dissociated hydrogen to drift deeper into the material, thereby confirming the positive charge state of atomic H in p-type SiC. The reactivation process was found to obey first-order kinetics for temperatures above 225C. From an analysis of the reactivation process we were able to determine the dissociation energy for the Al-H complex.

[1] M. E. Samiji, E. van Wyk, L. Wu, A. Venter and A. W. R. Leitch, Mater. Sci. Forum 353 - 356 (2001) 607.