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

Joanna Millunchick

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joannamm@umich.edu

2640 CSE

T: (734) 647-8980

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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a similar lattice mismatch, shows similar disordered (4x3) regions, but the highly ordered & beta2(2x4) regions have been replaced by &alpha2(2x4) regions.1 It is postulated that the (4x3) surface reconstruction is a unique alloy structure, while the (2x4) reconstructions are enriched in In.