Large periodic potential under lateral surface superlattices fabricated from heteroepitaxial stressor layers

We have fabricated lateral surface superlattices by etching a strained layer of In0.2Ga0.8As near the surface of a heterostructure. This provides strong modulation of the electron gas while retaining a high electron mobility. The potential arises mainly from strain and the piezoelectric effect, which depends on orientation, and from the change in the surface profile. The fundamental components of these two contributions cancel in one orientation to leave a dominant second harmonic. This effectively halves the period of the superlattice from its lithographic value and provides a promising technique for creating potentials with a period comparable to the Fermi wavelength.