Second harmonic generation from SimGen superlattices

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Abstract
We report the observation of optical second harmonic generation (SHG) from SimGen short‐period superlattices grown on different substrates. For a 775 nm fundamental beam, the SHG signals from odd‐odd, even‐even, and even‐odd specimens are comparable, apart from substrate‐dependent strain enhancement. It is concluded that the lack of a large bulk dipole‐allowed signal in odd‐odd superlattices predicted by Ghahramani, Moss, and Sipe [Phys. Rev. Lett. 64, 2815 (1990)] is due to the inevitable presence of monatomic steps on the substrate which lead to antiphase domains; a possible circumvention of this limitation is outlined based on the use of a single domain vicinal Si(001) substrate.