Hydrogen passivation and reactivation of the Al-acceptors in p-type6H-SiC

Abstract

We report on the passivation by hydrogen and the subsequent thermalreactivation of the acceptors in Al-doped p-type 6H-SiC. Capacitance-voltagemeasurements revealed that the near-surface free carrier concentration wasreduced by at least an order of magnitude after hydrogen plasma treatment. Thethermal stability of the Al-H complex in hydrogenated SiC was investigatedthrough a series of isothermal anneals at temperatures ranging from 200 to275 °C, while applying a reverse bias to a Ru Schottky barrier. Ruwas chosen as the Schottky barrier metal for both its permeability to hydrogenas well as its thermal stability. The electric field associated with theapplied reverse bias caused the dissociated hydrogen to drift deeper into thematerial, thereby confirming the positive charge state of atomic H in p-typeSiC. The thermal dissociation of the electrically neutral Al-H complex wasfound to obey first-order kinetics for temperatures above 225 °Cwith a dissociation energy of (1.51±0.12) eV.