Conduction band offset of HfO2 on GaAs

A detailed analysis of the band alignment between molecular beam deposited amorphous HfO2 and GaAs is reported. The conduction band offset, measured by internal photoemission (IPE), is 1.9 +/- 0.2 eV. The valence band offset (VBO) is probed by x-ray photoelectron spectroscopy (XPS). The accurate determination of the VBO requires a careful evaluation of differential charging phenomena and consequently a proper correction of the energy scale. The measured VBO value is 2.1 +/- 0.1 eV. Since the HfO2 gap is 5.6 eV, as detected by photoconductivity analysis, the results obtained by IPE and XPS are in excellent agreement.