Electronic effects on dislocation velocities in heavily doped silicon

Abstract

The electronic environment of the crystal markedly influences the velocity of dislocations in semiconductors. $n$-doping raises dislocation velocities in silicon over the undoped values. The behavior with $p$-doping is anomalous. For $T>\mathrm{}600\mathrm{}$°C $p$-doping does not change dislocation velocities. For $T<\mathrm{}600\mathrm{}$°C $p$-doping also increases the dislocation velocity, as found by Erofeev et al. The velocities of screw dislocations in $p$- and $n$-doped silicon have been investigated as a function of impurity concentration and temperature. The data can be explained using a model proposed by Frisch and Patel modified for Fermi-Dirac statistics, which assumes that the change in the dislocation velocity is proportional to the number of charged dislocation sites. In $n$-type silicon the dislocations behave as acceptors. A donor-like behavior is obtained for $p$-type silicon at $T<\mathrm{}600\mathrm{}$°C, with levels in both types near the gap center. The observed change in the activation energy of dislocations between heavily doped and undoped silicon can be readily calculated from the change in the Fermi level between the doped and undoped crystal with dislocations.