Hot electron transport in Au-HfO2-SiO2-Si structures studied by ballistic electron emission spectroscopy

Hot electron transport in Au-HfO2-SiO2-Si structures with 4 nm HfO2 and 1.5 nm SiO2 interfacial layer have been investigated by ballistic electron emission spectroscopy (BEES). By controlling the hot electron kinetic energy and injection current, distinctly different barrier heights can be measured. BEES sweeping below -5 V with 1 nA injection current yields high barrier heights (similar to 3.8 eV), attributable to the interfacial SiO2 layer. BEES sweeping from -6 V with high injection current (5 nA and above) induced localized breakdown of the SiO2 interfacial layer, allowing the barrier height of the HfO2 layer to be measured (similar to 1.9 eV). The energy-dependent effective mass of electrons in HfO2 is also determined by fitting oscillations in the BEES current. (c) 2007 American Institute of Physics.