Damaged and damage-free hydrogenation of GaAs: The effect of reactor geometry

The effects on GaAs hydrogenation of two different rf reactor types are investigated, one a parallel-plate reactor with a capacitively coupled discharge and the other an inductively coupled system. The atomic hydrogen, dissociated in the plasma of either system, passivates impurities in GaAs. The plasma in the capacitively coupled discharge reactor develops a large self-bias relative to the sample and large ion energies (∼100 eV), resulting in significant etching of the GaAs surface. In spite of the surface erosion, passivation of donors by hydrogen diffusing into the material is observed. The sample hydrogenated in the inductively coupled discharge (kT_e/q <1-2 eV) is not etched, exhibiting, nevertheless, a comparable passivation of donors. Hydrogenation without surface damage is accomplished with the sample in the glow discharge of an inductively coupled reactor but not in a capacitively coupled discharge.