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HL: Fachverband Halbleiterphysik

HL 63: III-V Semiconductors

HL 63.7: Vortrag

Freitag, 26. März 2010, 12:00–12:15, H13

Ferromagnetic and transport properties of very thin (Ga,Mn)As layers — •Lars Ebel, Stefan Mark, Michael Freitag, Tsvetelina Naydenova, Charles Gould, Karl Brunner, and Laurens W. Molenkamp — Physikalisches Institut (EP III), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

We have fabricated by low-temperature molecular beam epitaxy series of typically 4nm thin (Ga,Mn)As layers with homogeneous or parabolically graded Manganese content on un-GaAs(001). The average Mn content was varied between 2 and 10%. The samples have been studied by RHEED, SQUID, room- and low-temperature magneto-transport measurements. The results as well as self consistent model calculations by "nextnano" show a strong influence of hole compensation and band bending caused by LT-GaAs and surface defects. Thin layers with graded Mn content reveal better conductivity and higher Curie temperatures (up to about Tc=71K, as-grown) compared to homogeneous layers. Thus, such layer with moderate hole density but well-controlled transport and ferromagnetic behavior may be used for novel spintronic devices with large tunability by a gate voltage.