It is demonstrated using rapid thermal annealing that the electrical activation of Si+‐implanted GaAs capped with a plasma‐enhanced chemical vapor deposited (PECVD) silicon nitride (SixNy) layer requires longer annealing times compared to capless annealing. The SIMS profiles of2H from the GaAs samples onto which SixNycaps were deposited using deuterated ammonia showed that deuterium atoms diffuse readily into the implanted region during PECVD. The improvement in the electrical activation of the capped samples with annealing time correlates directly with decreasing concentration of the2H in the GaAs. It is postulated that the H atoms diffusing into GaAs during PECVD are trapped by the implantation‐induced damage and the delay in electrical activation corresponds to the time required for the release of the trapped H.