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(1 0 0)(2 × 1) and a-ZrO2/Ge(1 0 0)(2 × 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.