STRUCTURAL AND ELECTRONIC-PROPERTIES OF IDEAL NITRIDE AL INTERFACES/

The structural and electronic properties of the relaxed GaN/Al interfa ce are determined from first-principles local-density full-potential l inearized augmented plane-wave calculations. The atomic-site projected electronic density of states and the charge density, calculated as a function of the distance from the interface, show that the gap states induced into the semiconductor by the presence of Al are strongly loca lized in the interface region with a decay length lambda similar to 3. 5 a.u. We also study two related systems, the Al/AlN and GaN/AlN inter faces, both grown on a GaN substrate. Our results indicate that Al doe s not provide good Ohmic contacts on the atomically defect-free nitrid es considered, in contrast with experimental results on chemically tre ated GaN but in agreement with recent measurements on the clean surfac e. By comparing the three interfaces studied, we also find that the tr ansitivity rule is approximately satisfied and that small deviations m ust be attributed to differences in the interface morphology. [S0163-1 829(98)05008-5].