Energy gap and band alignment for (HfO2)x(Al2O3)1-x on (100) Si

High-resolution x-ray photoelectron spectroscopy (XPS) was applied to characterize the electronic structures for a series of high-k materials (HfO2)(x)(Al2O3)(1-x) grown on (100) Si substrate with different HfO2 mole fraction x. Al 2p, Hf 4f, O 1s core levels spectra, valence band spectra, and O 1s energy loss all show continuous changes with x in (HfO2)(x)(Al2O3)(1-x). These data are used to estimate the energy gap (E-g) for (HfO2)(x)(Al2O3)(1-x), the valence band offset (DeltaE(nu)) and the conduction band offset (DeltaE(c)) between (HfO2)(x)(Al2O3)(1-x) and the (100) Si substrate. Our XPS results demonstrate that the values of E-g, DeltaE(nu), and DeltaE(c) for (HfO2)(x)(Al2O3)(1-x) change linearly with x. (C) 2002 American Institute of Physics.