We demonstrate that periodic exposure to zero bias duringinsituhydrogenation of reverse‐biasedp‐type Schottky barrier structures has dramatic effects on H penetration. H influx can be slowed or even stopped by such protocols. By contrast, similar pulsing techniques produce almost no changes of penetration inn‐type barriers during hydrogenation; this latter observation is in sharp contrast to the expectations that charge conversion from H+to H−would reverse the drift of H species. We suggest that these effects are caused by the charge conversion of relatively immobile H‐related defects. In thep‐type barriers this results in a weakening or reversal of the near surface electric field, effectively stopping the drift of H+into the bulk. ©1996 American Institute of Physics.