The band structure of ALCVD AlZr- and AlHf-oxides as measured by XPS

This paper investigates the effect of thickness, composition and anneal temperature in N-2 on the band gap of the mixed oxide layer and the band offset with the Si substrate for layers grown by atomic layer deposition. For 1:1 (Al/Zr or Al/Hf) mixed oxides, the band gap reaches the bulk value for a thickness larger than 2 nm. In both cases (AlxZryOz and AlxHfyOz), the bulk values of the band gap show a linear dependence on the Al2O3 mol%, going from 5.6 (5) eV for pure ZrO2 (HfO2) to 6.7 eV for pure Al2O3. The effect of a post-deposition anneal on the band gap and the valence band alignment is also studied. Here, AlxHfyOz and AlxZryOz seem to act differently: while the annealing temperature does not have any influence on the band gap of AlxZryOz mixed oxide, the annealing in N-2 at temperature from 900degreesC generates an increase in the band gap value measured by XPS for AlxHfyOz. (C) 2003 Elsevier B.V. All rights reserved.