Anisotropic transport and nonparabolic miniband in a novel in-plane superlattice consisting of a grid-inserted selectively doped heterojunction

Abstract

Transport properties of electrons in a novel in-plane superlattice structure are studied and the field-effect transistor action has been demonstrated. The structure consists of an n-AlGaAs/GaAs modulation-doped heterojunction in which an array of monolayer-thick AlAs grid is embedded with an average period of 162 Å in the channel region of the heterojunction. This grid has been prepared with molecular beam epitaxy by depositing a half monolayer of AlAs on a GaAs (001) vicinal plane, where periodically spaced atomic terraces are formed. The electron mobilities μ∥,μ⊥ parallel and normal to the grid are measured as functions of electron concentration NS. While the mobility ratio (μ∥/μ⊥) is nearly unity at low NS, the ratio is found to get as large as 2.2 as NS increases. This anisotropic behavior of μ is well accounted for by the calculated nonparabolicity in the miniband structure of in-plane superlattices.