Band alignment of sputtered and atomic layer deposited SiO2 and Al2O3 on ScAlN.

The band alignments of two candidate dielectrics for ScAlN, namely, SiO₂ and Al₂O₂, were obtained by x-ray photoelectron spectroscopy. We compared the effect of deposition method on the valence band offsets of both sputtered and atomic layer deposition films of SiO₂ and Al₂O₃ on Sc_0.27Al_0.73 N (bandgap 5.1 eV) films. The band alignments are type I (straddled gap) for SiO₂ and type II (staggered gap) for Al₂O₃. The deposition methods make a large difference in relative valence band offsets, in the range 0.4–0.5 eV for both SiO₂ and Al₂O₃. The absolute valence band offsets were 2.1 or 2.6 eV for SiO₂ and 1.5 or 1.9 eV for Al₂O₃ on ScAlN. Conduction band offsets derived from these valence band offsets, and the measured bandgaps were then in the range 1.0–1.1 eV for SiO₂ and 0.30–0.70 eV for Al₂O₃. These latter differences can be partially ascribed to changes in bandgap for the case of SiO₂ deposited by the two different methods, but not for Al₂O₃, where the bandgap as independent of deposition method. Since both dielectrics can be selectively removed from ScAlN, they are promising as gate dielectrics for transistor structures. [ABSTRACT FROM AUTHOR]