| AVS 55th International Symposium & Exhibition | |
| Electronic Materials and Processing | Wednesday Sessions |
| Session EM-WeM |
| Session: | High-K Oxides and High Mobility Substrates |
| Presenter: | A.C. Kummel, University of California, San Diego |
| Authors: | E. Chagarov, University of California, San Diego A.C. Kummel, University of California, San Diego |
| Correspondent: | Click to Email |
Amorphous oxide-semiconductor interfaces are keys to the performance of all metal-oxide field effect transistors (MOSFETs), but little is known about the exact bonding geometry at the interface. In this study, the bonding of a single amorphous oxide onto three semiconductors is compared to understand selective bond formation and intermixing since interfaces with non-polar bonds, no intermixing, and no half-filled dangling bonds are optimal for MOSFET devices. The local atomic and electronic structure of a-Al2O3/Ge(100)(2x1), a-Al2O3/In0.5Ga0.5As, and a-Al2O3/In0.5Al0.5As/In0.5Ga0.5As interfaces were investigated by density-functional theory (DFT) molecular dynamics (MD) simulations. Realistic amorphous a-Al2O3 samples were generated using a hybrid approach including classical and DFT molecular dynamics. Each amorphous oxide/semiconductor interface was formed by placing an amorphous oxide sample on a slab of one of the semiconductors and annealing the stack at 700K / 800K and 1100K; subsequently, the stack was cooled and relaxed to get the final oxide-semiconductor interfacial bonding structure. The a-Al2O3/Ge interface demonstrates strong chemical selectivity with Al atoms migrating out of interface into the oxide bulk and O atoms migrating into the interface region resulting in interface bonding exclusively through Al-O-Ge bonds creating a large interface dipole; this exclusive Al-O-Ge bonding is due to Al-O bonds being more energetically favorable than Al-G bonds. During annealing of a-Al2O3/In0.5Al0.5As/In0.5Ga0.5As, Al migrates from InAlAs to a-Al2O3, demonstrating interfacial mixing; the intermixing is driven by the high energy of formation for Al-O bonds. The a-Al2O3/In0.5Ga0.5As interface has polar As-Al bonds and In/Ga-O bonds of opposite dipole direction, low lattice distortion, and no intermixing. The formation of two types of bonds with opposite dipoles is driven by electronegativity: Al, an electron donor, bonds to As an electron acceptor while O, an electron acceptor bonds to In/Ga, electron donor.