Increase in current density for metal contacts to n-germanium by inserting TiO2 interfacial layer to reduce Schottky barrier height

Metal contacts to n-type Ge have poor performance due to the Fermi level pinning near the Ge valence band at metal/Ge interfaces. The electron barrier height can be reduced by inserting ultrathin dielectrics at the metal-semiconductor interface. However, this technique introduces tunneling resistance from the large conduction band offset (CBO) between the insulator and Ge. In this work, the CBO between TiO2 and Ge is estimated to range from -0.06 to -0.26 eV so tunneling resistance can be reduced. By inserting 7.1 nm TiO2 between Al and n-Ge, current densities increased by about 900x at 0.1 V and 1200x at -0.1 V compared to contacts without TiO2. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562305]