Resistivity of Dilute 2D Electrons in an Undoped GaAs Heterostructure

Abstract

We report resistivity measurements from 0.03 to 10 K in a dilute high mobility 2D electron system. Using an undoped $\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ heterojunction in a gated field-effect transistor geometry, a wide range of densities, $0.16\times {10}^{10}$ to $7.5\times {10}^{10}{\mathrm{c}\mathrm{m}}^{-2}$, are explored. For high densities, the results are quantitatively shown to be due to scattering by acoustic phonons and impurities. In an intermediate range of densities, a peak in the resistivity is observed for temperatures below 1 K. This nonmonotonic resistivity can be understood by considering the known scattering mechanisms of phonons, bulk, and interface ionized impurities. Still lower densities appear insulating to the lowest temperature measured.