Using ab initio calculations, we compare the effects produced on the Al/GaA
s(100) Schottky barrier height by Ge and Si interface layers with thickness
ranging from 0 to 2 monolayers. The dipole layers, generated by the group-
IV atomic substitutions at the interface, increase/decrease the p-type Scho
ttky barrier at the As-/Ga-terminated Al/GaAs(100) junction. Although the t
rends with Ge and Si interlayers are similar for coverages less than 0.5 mo
nolayers, at higher coverages the Schottky barrier exhibits a stronger nonl
inear behavior, and smaller barrier variations, in Al/Ge/GaAs(100) than in
Al/Si/GaAs(100). In particular, at a coverage of 2 monolayers, the use of G
e interlayers instead of Si ones reduces by 25% the barrier tunability. The
se trends are at variance with those predicted by existing macroscopic band
-structure models, and our results should help in discriminating between di
fferent mechanisms of Schottky barrier tuning. (C) 2000 American Vacuum Soc
iety. [S0734-211X(00)00204-3].