Weak Localization in an Ultradense 2D Electron Gas in δ-doped Silicon

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An ultradense 2D electron system can be realized by adsorbing PH₃ precursor molecules onto an atomically clean Si surface, followed by epitaxial Si overgrowth. By controlling the PH₃ coverage the carrier density of such system can easily reach 10¹⁴ cm⁻², exceeding that typically found in GaAs/AlGaAs structures by more than two-three orders of magnitude. We report on a first systematic characterization of such novel system by means of standard magnetotransport. The main findings include logarithmic temperature dependence of zero-field conductivity and logarithmic negative magnetoresistance. We analyzed the results in terms of scaling theory of localization in two dimensions.