Hydrogen passivation and reactivation of the Al-acceptors in p-type 6H-SiC

We report on the passivation by hydrogen and the subsequent thermal reactivation of the acceptors in Al-doped p-type 6H-SiC. Capacitance-voltage measurements revealed that the near-surface free carrier concentration was reduced by at least an order of magnitude after hydrogen plasma treatment. The thermal. Stability of the AI-H complex in hydrogenated SiC. was investigated through a series of isothermal anneals at temperatures ranging from 200 to 275 degreesC, while applying a reverse bias to a Ru Schottky barrier. Ru was chosen as the Schottky barrier metal for both its permeability to hydrogen as well as its thermal stability. 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 thermal dissociation of the electrically neutral Al-H complex was found to obey first-order kinetics for temperatures above 225 degreesC with a dissociation energy of (1.51 +/-0.12) eV.