Deep levels in semiconductors

Abstract

The 3d transition element ion impurities in silicon are reviewed for the broad insight they provide in understanding deep levels in semiconductors. As interstitials, their interaction with the host tends to confine the d-levels to the forbidden gap, providing many deep states. The interaction at the substitutional site is best considered as an interaction with the lattice vacancy, into which the impurity is placed. This interaction tends to repel deep a1 and t2 levels from the gap. When the levels are present, they are mostly vacancy-like and the defect is likely to display the large lattice relaxations characteristic of the vacancy.