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approvedosi_11_art_abstract_with_picture_farbod.pdf2015-06-15 16:21:48Farbod Shafiei


Author: Farbod Shafiei
Requested Type: Poster
Submitted: 2015-05-29 19:16:27

Co-authors: Tommaso Orzali, Alexey Vert, Michael Downer

Contact Info:
The University of Texas at Austin
2511 Speedway
Austin, Texas   78712
United States

Abstract Text:
A long-range goal of semiconductor manufacturing is integration of III-V semiconductor films onto Si substrates, to exploit the high carrier mobility and light-emitting properties of III-V devices within the established Si platform. A fundamental problem with polar-nonpolar hetero-interfaces is that natural single-atom steps on the substrate precipitate formation of submicron anti-phase domains (APDs) in the epi-film, the boundaries of which scatter carriers, degrading mobility.
Nanoscale patterning of Si substrates with SiO2 pillars is an established method for suppressing threading dislocations [1] via aspect ratio trapping (ART). Recently evidence that ART structures may also suppress APDs has emerged [2]. However, APD density was diagnosed invasively and indirectly via SEM.
Here we use non-invasive SHG microscopy [3] to diagnose APDs directly by observing effects of sign reversal of the nonlinear optical susceptibility chi(2) in neighboring domains. ART structuring of the substrate greatly enhances far-field SHG by reducing destructive interference from neighboring APDs. Nearfield scanning SHG microscopy yields additional information on local strain in the growing epi-film.

[1] J. Bai et al., Appl. Phys. Lett. 90, 101902 (2007);
[2] J. Li et al. J. Cryst. Growth 311, 3133 (2009);
[3] M. Lei et al., Appl. Phys. Lett. 102, 152103 (2013).