Joanna Millunchick

Professor

joannamm@umich.edu

2014 HH Dow

T: (734) 647-8980

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Atomic Surface Structure in Compound Semiconductor Alloys: Novel Reconstructions in InGaAs Alloys

Sponsor: National Science Foundation
The epitaxial growth of III-V semiconductors and their corresponding properties depend on the surface reconstructions and morphology of the film grown. We have found that the surface structure of InxGa1-xAs alloys consists of multiple surface reconstructions depending on the composition x. The goal of this work is to determine which reconstructions are present as a function of both composition and temperature, in order to map out the surface phase diagram for this system. For example, for In0.81Ga0.19As/InP grown at 503¡C with an As overpressure of 2.1 ML/sec and a growth rate of 1.16 ML/sec, highly ordered regions of &beta2(2x4) coexist with more disordered regions having a (4x3) symmetry. In this case, the percentage of &beta2(2x4) covering the surface initially increases with increasing thickness, followed by a sharp decrease that corresponds to the onset of surface roughening and 3D roughening. Previous work on In0.27Ga0.73As/GaAs, which has a similar lattice mismatch, shows similar disordered (4x3) regions, but the highly ordered & beta2(2x4) regions have been replaced by &alpha2(2x4) regions.1 It is postulated that the (4x3) surface reconstruction is a unique alloy structure, while the (2x4) reconstructions are enriched in In.
Highlights (Click an image for more information)
  • STM image of InGaAs surface

    Scanning tunneling microscopy image of the β2(2x4) reconstruction of InGaAs, this surface also developed a pit.

  • Simulated STM image of Mirecki-Millunchick (4x3) model

    This is a forward and reverse bias image of the Mirecki-Millunchick model for InGaAs (4x3) reconstruction.

  • Simulated STM image of SSJ Model

    Simluated filled and empty state image of InGaAs (4x3) reconstruction proposed by Sauvage-Simkin and modified by the Jones group. Surface Science, V. 600 (2006) 973-982