S. Picozzi et al., Metal-induced gap states and Schottky barrier heights at nonreactive GaN/noble-metal interfaces, PHYS REV B, 61(24), 2000, pp. 16736-16742
We present ab initio local density FLAPW calculations on nonreactive N-term
inated [001] ordered GaN/Ag and GaN/Au interfaces and compare the results (
such as metal induced gap states and Schottky barrier heights) with those o
btained for GaN/Al, in order to understand the dependence of the relevant e
lectronic properties on the deposited metal. Our results show that the dens
ity-of-gap states is appreciable only in the first semiconductor laver clos
e to the interface. The decay length of the gap states in the semiconductor
side is about 2.0+/-0.1 Angstrom and is independent of the deposited metal
, therefore being to a good extent a bulk property of GaN. Our calculated v
alues of the Schottky barrier heights are Phi(Bp) (GaN/Ag) = 0.87 eV and Ph
i(Bp) (GaN/Au) = 1.08 eV; both values are smaller than the GaN/Al Value [Ph
i(Bp) (GaN/Al) = 1.51 eV] and this quite large spread of values excludes th
e possibility of a Fermi-level pinning within the GaN band gap. Because of
the low screening in GaN, the potential barrier at the junction is strongly
affected by the structural arrangement of the first metal layer at the int
erface. This leads to quite large variations of the Schottky barrier height
as a function of the metal. in contrast with the behavior of GaAs/metal in
terfaces.