Metal/III–V effective barrier height tuning using ALD high-κ dipoles

Abstract

In summary, we successfully demonstrate RC and ΦB,eff tuning of Al/n-GaAs junctions by a MIS diode structure using ALD HfO2, TiO2, and ZrO2 dielectrics. We also introduce for the first time the use of HfO2/TiO2, two high-κ dielectrics in combination to further shift the Fermi level and reduce ΦB,eff. The underlying mechanism is believed to be the formation of a high-κ/high-κ dipole, which opens doors to the exploration of a multitude of other high-κ/high-κ dielectrics to ultimately achieve ΦB,eff ≤ 0. This MIS structure provides much flexibility in the design of ideal source/drain contacts for III–V MOSFETs and Schottky Barrier FETs, where in real applications highly doped substrates would significantly reduce RC and ΦB,eff. Further study of the dipole interaction and effective work function will lead to a better understanding of the physics behind metal/III–V contacts.