AVS 46th International Symposium
    Nanometer-scale Science and Technology Division Tuesday Sessions
       Session NS-TuA

Paper NS-TuA1
Size, Shape, Strain, and Composition Inhomogeneities of In@sub 0.5@Ga@sub 0.5@As QDs Grown by Migration Enhanced Epitaxy

Tuesday, October 26, 1999, 2:00 pm, Room 612

Session: Innovative Nanoscale Measurements
Presenter: N. Liu, The University of Texas at Austin
Authors: N. Liu, The University of Texas at Austin
C.K. Shih, The University of Texas at Austin
O. Baklenov, The University of Texas at Austin
A.L. Holmes, Jr., The University of Texas at Austin
Correspondent: Click to Email
We report cross-sectional scanning tunneling microscopy (XSTM) studies of In@sub 0.5@Ga@sub 0.5@As self-assembled quantum dots (SAQD) grown using migration enhanced epitaxy (MEE). Samples were cleaved in-situ to reveal either (110) or (1-10) cross-sectional surfaces. For the 10 ML QDs, they exhibit truncated-pyramid shapes with well-defined facets on both (110) and (1-10) projections. On the (110) surface, the orientation of the facets is about 35 degrees with respect to the base of the QDs, and on the (1-10) surfaces about 25 degrees with respect to the base. The average height of the 10 ML QDs is about 10 nm, while the average base length is about 45 nm along the (110) projection and about 61 nm along the (1-10) projection. We further discovered that the In-concentration in this kind of truncated-pyramid shaped QDs is inhomogeneous. In fact the qualitative concentration contours at high concentration show an inverted triangle shape. Similarly the distribution of the lattice parameters (as determined from the STM) within and around the QD is also inhomogeneous with its inhomogeneity consistent with an inverted triangle shape of high In-concentration in the QD. Detailed analysis and possible mechanism responsible for such a concentration distribution profile will be discussed.