Comment on "Interstitial hydrogen and neutralization of shallow-donor impurities in single-crystal silicon"

Abstract

It has been well established that shallow acceptor impurities in single-crystal silicon can be neutralized by exposure to monoatomic hydrogen. On the other hand, several studies have concluded that shallow donor impurities in silicon cannot be passivated. Contrary to these previous conclusions, Johnson, Herring, and Chadi1 have recently reported neutralization of phosphorus by hydrogenation. Here we show that a detailed analysis of the electrical measurements in Ref. 1 indicates that P neutralization is not necessarily implied. The results can also be explained as a combined effect of generation of H-associated acceptors in the $n^+$ layer and neutralization of substrate boron in the p region. The former reduces the effective free-electron concentration and also the effective mobility as discussed by Johnson, Herring, and Chadi. The effect of the latter is to increase the effective mobility. Since this latter effect was not taken into account in Ref. 1, donor neutralization was considered as the only possibility.