N2 AND N4 OPTICAL-TRANSITIONS IN DIAMOND - A BREAKDOWN OF THE VACANCYMODEL

The vacancy model for impurity vacancy defects in semiconductors assum es that the ground and low-energy excited states are derivable from th e four sp(3) hybrid orbitals on atoms bordering the vacancy. There are many cases where this model works but We describe here a counterexamp le concerning the lowest excited state of the [V-N-3] defect in diamon d. It is shown that a shallow electron trap, localized outside the vac ancy, is involved in the first excited state and responsible for the N 2 and N4 optical bands associated with the defect.