| AVS 54th International Symposium | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM-ThA |
| Session: | High-K/High Mobility Substrates and Power Electronics |
| Presenter: | J.B. Clemens, University of California, San Diego |
| Authors: | J.B. Clemens, University of California, San Diego A.C. Kummel, University of California, San Diego |
| Correspondent: | Click to Email |
Hafnium oxide (HfO2) has been successfully used as a high-κ gate oxide on Si(100) and is being investigated as a high-κ gate oxide for high mobility III-V semiconductors. To form an electronically passive interface on a III-V semiconductor is challenging because the bonding to the group III and group V atoms must be distinct to leave both atoms in their bulk oxidation states with an unchanged electronic structure. The bonding of Hf, O, and HfO2 on the InAs(001)-(4x2)/c(8x2) surface was probed with scanning tunneling microscopy (STM) to determine the exact bonding positions at low coverage. The InAs(001)-(4x2) surface is advantageous for these studies since it has a row and trough structure with In atoms at the center of the rows and As atoms at the edges of the rows which are easy to image in STM. Furthermore, the InAs(001)-(4x2) surface contains no As-As dimers so surface atoms are rarely displaced during oxide and oxygen dosing. Although the sticking probability for O2 on this surface is very low (~0.015%), it is found that O2 bonds preferentially to the first layer undercoordinated In rows. This is consistent with O-metal bond formation being thermodynamically more favorable than As-O bond formation. Furthermore, the As atoms on the edge of the row have only half-filled dangling bonds so they are poor electron donors and less likely to react with oxygen than As dimer atoms found on other III-V reconstructions. Conversely, STM shows that Hf bonds initially to the second-layer tricoordinated As atoms along the edges of the In rows of the InAs(001)-(4x2) surface. This is consistent with the Hf atoms donating electrons to the unfilled dangling bonds of the second layer tricoordinated As atoms. In order to investigate the bonding geometry of HfO2 on the InAs(001)-(4x2) surface, Hf and O2 are co-deposited. Current work will show the result of annealing these surfaces in order to create ordered submonolayer coverages of HfO2.