Magnetotransport in InP-based dilute single δ layers

We have investigated the magnetotransport in InP sulphur-doped δ-layer structures. In contrast to GaAs-based systems, it was possible to measure single δ layers in the concentration range between ${10}^{15}$ and ${10}^{16}$ ${\mathrm{m}}^{\mathrm{-}2}$ where a metal-insulator transition is expected. At low magnetic fields perpendicular to the sample we observed a giant negative magnetoresistance (∼30% at 4.2 K), followed by an exponential increase in magnetoresistance at high fields. The behavior of the minimum shows certain features of the quantum Hall effect corresponding to a filling factor of 2. The experimental data are interpreted with the help of a strong-weak–localization transition-phase diagram in a disordered two-dimensional electron gas constructed using a simple lucid model.