Atomic Layer Deposited Bilayers and the Influence on Metal-Insulator-Semiconductor Schottky Barriers

Atomic layer deposited oxide bilayers have been investigated as a means to tune the Schottky barrier height of metal-insulator-semiconductor contacts. Inserting LaO
x
between AlO
x
and a hydrogen-terminated silicon substrate increased the average Schottky barrier height of both n- and p-type silicon contacts by up to 0.14 eV. When the substrate was terminated with a chemical oxide, or the LaO
x
was inserted above the AlO
x
instead, the direction of the barrier height shifts was insensitive to the deposition order of the high-k oxides. LaO
x
, insertion then increased the p-type barrier height by 0.04-0.05 eV and decreased the n-type barrier height by 0.20-0.47 eV. Possible mechanisms for the shifts are discussed, including oxygen areal density differences, Fermi level depinning, and oxide charges. The data presented demonstrate new and more complex dielectric layer stacks to tune contact properties in metal-insulator-semiconductor structures.