BONDING PROPERTIES OF THE INTERACTING DONOR AND ACCEPTOR STATES OF SI-DOPED NIPI STRUCTURES IN GAAS

Two-layer idealized Si-doped NIPI structures in GaAs show (1) non-bond ing character for the acceptor state and (2) significant antibonding f eatures for the donor state. These properties cannot be anticipated fr om the simple bonding picture deduced from the results of the delta-la yer NIPI structures-the host crystal can be treated simply as a dielec tric background. We attributed (1) to the consequence of minimizing th e kinetic energy of the acceptor state to avoid localizing its charge at the Ga atom which is the common nearest neighbor of the two accepto r atoms. The physical origin for (2) is shown to be equivalent to the Coulomb repulsion between the valence states of the host crystal and t he donor state. The results of the two-layered NIPI case, especially f or the donor state, illustrate explicitly that the occupied states of the host crystal can play an important role in determining the bonding properties of impurity states.