Formation mechanisms of polar and non-polar amorphous oxide-semiconductor interfaces

The formation mechanisms of polar and nonpolar interfaces were investigated by density-functional theory molecular dynamics simulations of the atomic structure of the a-Al2O3/Ge(100)(2 x 1) and a-ZrO2/Ge(100)(2 x 1) interfaces. The a-Al2O3/Ge interface demonstrates strong chemical selectivity resulting in interface bonding exclusively through Al-O-Ge bonds. The a-ZrO2/Ge interface has both Zr-O-Ge and O-Zr-Ge bonds. The a-ZrO2/Ge junction creates a much less polar interface with lower deformation and intermixing than a-Al2O3/Ge consistent with experimental measurements. In both cases, the interface polarity is determined by the stoichiometry of the interface bonding as opposed to charged defect formation. (c) 2008 Elsevier B.V. All rights reserved.