Effect of hydrogen on shallow dopants in crystalline silicon

Passivation of shallow impurities by H has been attributed to H-impurity pairing in both p-type and n-type Si. We show that existing interpretations of data were based on contradictory assumptions and that a coherent interpretation of all the data can only be obtained if one assumes that diffusing H has a donor level in the gap. A novel interpretation emerges: In p-type material, passivation is due to direct compensation, so that pairing is a consequence, not a cause of passivation; in n-type material, passivation is indeed due to pairing, but is suppressed by H2 formation and possibly other reactions. Several predictions are made and new experiments are proposed as tests.