AVS 50th International Symposium
    Semiconductors Thursday Sessions
       Session SC+MI-ThA

Paper SC+MI-ThA4
Cross-sectional STM Study of Mn-doped GaAs*

Thursday, November 6, 2003, 3:00 pm, Room 321/322

Session: Ferromagnetic and Dilute Magnetic Semiconductors
Presenter: J.M. Sullivan, Naval Research Laboratory
Authors: J.M. Sullivan, Naval Research Laboratory
G.I. Boishin, Naval Research Laboratory and Nova Research Inc.
S.C. Erwin, Naval Research Laboratory
L.J. Whitman, Naval Research Laboratory
A.T. Hanbicki, Naval Research Laboratory
B.T. Jonker, Naval Research Laboratory
Correspondent: Click to Email
When doped with Mn, GaAs exhibits long-range ferromagnetic order at temperatures up to ~150K. It is generally believed that ferromagnetism in GaMnAs is mediated by holes created by the substitution of Mn for Ga. Recent studies have suggested that a substantial amount of Mn is also present at interstitial sites, where Mn acts as a donor, partially compensating the holes and reducing the Curie temperature. To characterize the location and electronic configuration of Mn in device-quality Mn-doped GaAs, we have combined the complementary techniques of cross-sectional scanning tunneling microscopy (XSTM) and density functional theory (DFT). XSTM was used to atomically characterize a GaMnAs film across a single {110} cleavage plane. We used DFT to help interpret our images by theoretically simulating the XSTM image of Mn near the GaAs(110) surface. We considered Mn occurring as substitutionals, interstitials, and substitutional-interstitial complexes; a range of physically plausible charge states was considered for each. Defects in the first four layers near the surface were studied. STM filled-state images were simulated at the level of Tersoff-Hamann theory by integrating the local density of states over an energy window given by the experimental bias voltage. Thus, these complementary techniques allow us to identify Mn-related defects in the GaAs zinc-blende structure. *Supported by the US Office of Naval Research and the Defense Advanced Research Projects Agency.