Influence of shallow impurity on steady-state probability function of multilevel deep impurity

Abstract

The deep impurity added into the n- or p-type semiconductor is partially ionised. The probability function used to describe the occupation of a deep energy level, is the Fermi-Dirac function into which the entropy factor is introduced; /spl chi//sub p/ for donor level or /spl xi//sub n/ for acceptor level. The entropy factors are used to adjust the calculated and measured values. An effective deep energy level was defined depending on the predicted position of a deep level and on obtained entropy factor. Comparing the calculated and measured values for gold and platinum added into the n- and p-type silicon, we can see that the same predicted energy level is described with a quite different entropy factor in the n- and p-type semiconductor. According to the obtained positions of the effective deep energy levels, it can be concluded that in the compensation between shallow and deep impurity a deep level, which is nearest to the shallow level, must be considered. The other levels are neutral. It might happen that in the n-type semiconductor the higher acceptor level of platinum is occupied, while the lower one is empty. It seems that such a neutral energy level does not exist in the n-type, while in the p-type it does, and it is partially occupied.