Band gap and band discontinuities at crystalline Pr2O3/Si(001) heterojunctions

Abstract

We report the experimental results on the band alignment of Pr2O3 films on Si(001) as prepared by molecular beam epitaxy. Using x-ray photoelectron spectroscopy, we obtain a valence band offset at the Pr2O3/Si(001) interface of (1.1±0.2) eV. High field tunneling was used to extract the conduction band offset of (0.5–1.5) eV. Thus, the Pr2O3/Si(001) interface band alignment is symmetric, desired for applying such materials in both n- and p-type devices. The band gap of bulk Pr2O3 should be between 2.5 and 3.9 eV. Using scanning tunneling spectroscopy, we find a surface-state band gap of about 3.2 eV for monolayer coverage. In agreement with recent pseudopotential calculations, the electron masses in the oxide appear to be very large. This effect, together with the suitable band offsets lead to the unusually low leakage currents recently measured.