Role of dangling bonds at Schottky barriers and semiconductor heterojunctions

Abstract

It is shown that the Schottky-barrier height and the band offset at semiconductor heterojunctions can coherently be related through the energy of dangling bonds. At Schottky barriers the dangling bonds become resonant states, in which case the Friedel sum rule imposes that the dangling-bond energy aligns with the metal Fermi energy. For heterojunctions the condition of negligible charge transfer corresponds to an alignment of the dangling-bond energies. The proposed theory naturally allows an identification of Tersoff’s midgap level with the dangling-bond energy. Detailed calculations are worked out in a charge-dependent tight-binding scheme and show good correlation with experimental data, confirming the validity of the description.