| AVS 54th International Symposium | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM-ThA |
| Session: | High-K/High Mobility Substrates and Power Electronics |
| Presenter: | A.C. Kummel, University of California, San Diego |
| Authors: | E.A. Chagarov, University of California, San Diego A.C. Kummel, University of California, San Diego |
| Correspondent: | Click to Email |
Density-Functional Theory simulations of interface formation between amorphous Al2O3 oxide and Ge(001)-(2x4) surface were performed to model the chemical bonding at the oxide-semiconductor interface. A realistic DFT sample of amorphous Al2O3 was developed using “melt and cool” hybrid Classical-DFT Molecular Dynamics (MD) approach. Initially, 24 samples of 100 atoms were prepared by classical MD runs by melting initially crystalline sample. The spatial distribution of the atoms in each sample was quantified using Radial Distribution Functions (RDF), coordination distribution, and average coordination number. The sample with an atomic spatial distribution closest to the experimental geometry was DFT annealed to obtain a more realistic fully relaxed DFT geometry. The DFT annealed a-Al2O3 sample was placed on a 8 layer Ge(001)-(2x4) slab and partially relaxed for 200 steps with the fixed Ge atoms allowing the a-Al2O3 to adjust to Ge surface topography and to form oxide-Ge bonds. Subsequently, the top 5 layers of Ge were unfrozen, and the whole a-Al2O3-Ge system was annealed, cooled and relaxed to form a-Al2O3-Ge interface. DFT simulations of a-Al2O3-Ge interface revealed that during annealing, Al atoms migrate out of interface, while O atoms migrate into the interface. The bonding of a-Al2O3 to Ge occurs mainly through O atoms forming a low density Al-O-Ge bonds to the Ge dangling bonds on the surface. It was found that several O atoms diffused into Ge bulk forming interstitials. Electronic structure analysis of the interface demonstrated that Density of States (DOS) of the interface region was approximately a superposition of a-Al2O3 and Ge(001)-(2x4) DOS curves without significant new features. The oxygen-rich a-Al2O3/Ge interface is consistent with Al forming stronger bonds to O than to Ge and with experimental results. The small changes in electronic structure for a-Al2O3/Ge interface formation are consistent with the oxide reducing the number of Ge dangling bonds and only forming a low density of weakly ionic Al-O-Ge bonds.