| AVS 55th International Symposium & Exhibition | |
| Electronic Materials and Processing | Wednesday Sessions |
| Session EM-WeM |
| Session: | High-K Oxides and High Mobility Substrates |
| Presenter: | J. Shen, University of California, San Diego |
| Authors: | J. Shen, University of California, San Diego A.C. Kummel, University of California, San Diego |
| Correspondent: | Click to Email |
We have used scanning tunneling microscopy (STM) and density functional theory (DFT) calculations to both identify the group III rich III-V surface reconstruction and to identify the bonding structure for oxide on these surfaces. In-rich InAs(001)-(4×2) can readily be prepared by decapping of As2 capped InAs(001) wafers. STM results reveal that In-rich InAs(001)-(4×2) has a very different atomic structure than Ga-rich GaAs(001)-ζ(4×2) structure even though the surfaces have similar symmetry. The InAs(001)-(4×2) is denoted as the β3(4×2) and has a unit cell consisting of two undimerized group III atoms on the row and two group III dimers in the trough. STM results showed that the initial deposited In2O molecules bond to the edges of the rows and most likely form new In-As bonds to the surface without any disruption of the clean surface structure. Annealing the In2O/InAs(001)-(4×2) surface at 400˚C results in formation of flat order monolayer rectangular islands onto which oxide grows in a layer-by-layer mechanisms with amorphous structure. In0.53Ga0.47As is a good candidate for a III-V MOSFET due to its high carrier mobility, low density of thermal carriers, and ability to be grown lattice matched on semi-insulator InP substrates. STM images of the clean surface indicate that the In0.53Ga0.47As(001)-(4×2) surface reconstruction is similar to the InAs(001)-(4×2) structure. The DFT calculations reveal that the some of the trough dimers are buckled, which is consistent with the STM images showing that the trough has poor order. Ga2O was deposited on the surface to determine how oxide adsorbates bond to In0.53Ga0.47As(001)-(4×2) clean surface. The bonding structure of the annealed Ga2O/In0.53Ga0.47As(001)-(4×2) is similar to that of In2O/InAs(001)-(4×2); however, the Ga2O/ In0.53Ga0.47As(001)-(4×2) islands are more weakly ordered than the In2O/InAs(001)-(4×2) islands. For both In2O/InAs(001)-(4×2) islands and Ga2O/ In0.53Ga0.47As(001)-(4×2), the oxide adsorbates never cause the abstraction of any surface atoms on the InAs and In0.53Ga0.47As(001)-(4×2) surfaces; furthermore, for monolayer oxide films, the oxide molecules only occupied specific sites. After high temperature annealing, the oxide desorbs from the surface and the clean (4×2) surface is restored. This is consistent with the formation of a smooth interface between the oxide and the semiconductor.