The structural and electronic properties of the GaN/Al interface are determined from first principles local density full potential linearized augmented plane wave (FLAPW) calculations. The charge distribution of the gap states as a function of the distance from the interface shows that the gap states induced into the semiconductor by the presence of Al are strongly localized in the junction region. Furthermore, we find that Al does not provide good ohmic contacts on the clean nitrides considered, in contrast with experimental results on chemically treated GaN, but in agreement with recent measurements on the clean surface. We also study some auxiliary systems (all grown on a GaN substrate), i.e. the Al/AlN interface, the GaN/AlN heterojunction and the GaN/Al with an AlN intralayer (GaN-AlN/Al). The transitivity rule for the GaN/Al, AlN/Al and GaN/AlN interfaces is fairly well satisfied and small differences must be ascribed to differences in the interface morphology. Finally, we find that the AIN intralayer does not significantly affect the p-type Schottky barrier height of the GaN/Al interface.
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The authors greatfully acknowledge N.Newman, V. Bermudez and N. Binggeli for stimulating discussions. This work was supported by a supercomputing grant at Cineca (Bologna, Italy) through the Istituto Nazionale di Fisica della Materia (INFM), by the MRSEC program of the National Science Foundation (DMR-9632472) at the Materials Research Center of Northwestern University and by a grant of computer time at the NSF-supported Pittsburgh Supercomputing Center.
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Picozzi, S., Continenza, A., Massidda, S. et al. Structural and Electronic Properties of GaN/AL Interfaces. MRS Online Proceedings Library 482, 845–850 (1997). https://doi.org/10.1557/PROC-482-833