| AVS 54th International Symposium | |
| Magnetic Interfaces and Nanostructures | Thursday Sessions |
| Session MI-ThM |
| Session: | Magnetic Semiconductors I |
| Presenter: | E.N. Yitamben, University of Washington |
| Authors: | E.N. Yitamben, University of Washington T.C. Lovejoy, University of Washington I.N. Gatuna, University of Washington F.S. Ohuchi, University of Washington M.A. Olmstead, University of Washington |
| Correspondent: | Click to Email |
The intrinsic vacancy semiconductor Ga2Se3, which may be grown epitaxially on Si, poses several interesting issues for the study of dilute magnetic semiconductors. Substitution of transition metal impurities may occur on either occupied or vacant cation sites in the defected zincblende lattice. For dopants with different valence from the host cation, this may result in self-compensation of donors and acceptors, while an isoelectronic impurity can either add electrons by inserting into a vacancy, or minimally disturb the band structure by replacing a Ga. To probe the interrelationship between magnetism and free carriers in this new class of dilute magnetic semiconductors, we have performed both theoretical and experimental investigations of Cr-doped Ga2Se3 grown epitaxially on Si(001):As. Scanning tunneling microscopy shows nucleation of anisotropic islands, with the area between islands similar to pure Ga2Se3. The size and shape of the islands is dependent both on Cr concentration and on whether or not a pure Ga2Se3 buffer layer is deposited first. Despite the similar intrinsic valence between Cr and Ga, addition of a few percent Cr to Ga2Se3 results in metallic bands with minimal dispersion and leads to significant changes of the Se local environment, as measured with high resolution photoemission spectroscopy. These results may indicate Cr substituting into a vacancy rather than replacing Ga, or possibly creating local areas of CrSe, which computations show to be half-metallic. At higher concentrations, X-ray absorption and photoemission show two distinct Cr environments.
This work was supported byt NSF grant DMR 0605601. TCL acknowledges support from NSF/NCI IGERT DGE-0504573. Some of the research was pursued at the Advanced Light Source, which is supported by the DOE under contract DE-AC02-05CH11231.