Search

We present a study of the temperature and density dependence of the resistivity of an extremely high quality two-dimensional hole system grown on the (100) surface of GaAs. For high densities in the metallic regime ($p\agt 4 \times 10^{9}$ cm$^{-2}$), the nonmonotonic temperature dependence ($\sim 50-300$ mK) of the resistivity is consistent with temperature dependent screening of residual impurities. At a fixed temperature of $T$= 50 mK, the conductivity vs. density data indicates an inhomogeneity driven percolation-type transition to an insulating state at a critical density of $3.8\times 10^9$ cm$^{-2}$., Comment: accepted for publication in PRL

We present low-temperature magnetoconductivity measurements of a density-tunable and high mobility two-dimensional electron gas confined in the wide band-gap $\mathrm{Ga}\mathrm{N}∕\mathrm{Al}\mathrm{Ga}\mathrm{N}$ system. We observed pronounced antilocalization minima in the low-field conductivity, indicating the presence of strong spin-orbit coupling. Density dependent measurements of magnetoconductivity indicate that the coupling is mainly due to the Bychkov-Rashba mechanism. In addition, we have derived a closed-form expression for the magnetoconductivity, allowing us to extract reliable transport parameters for our devices. The Rashba spin-orbit coupling constant is ${\ensuremath{\alpha}}_{\mathrm{so}}\ensuremath{\sim}6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}\phantom{\rule{0.3em}{0ex}}\mathrm{eV}\phantom{\rule{0.2em}{0ex}}\mathrm{m}$, while the conduction-band spin-orbit splitting energy amounts to ${\ensuremath{\Delta}}_{\mathrm{so}}\ensuremath{\sim}0.3\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ at ${n}_{e}=1\ifmmode\times\else\texttimes\fi{}{10}^{16}\phantom{\rule{0.3em}{0ex}}{\mathrm{m}}^{\ensuremath{-}2}$.