Two-dimensional electron gas formed in a back-gated undoped heterostructure

Abstract
By using a back-gate operation, a high-quality two-dimensional electron gas(2DEG) is formed in an undoped GaAs/AlGaAs inverted heterostructure. A high mobility of around 3×10 6 cm 2 /V s at 1.6 K is obtained for the structure without any compensating surfacedoping. The electron density is controllable down to 7×10 9 cm −2 . The relation between electron density and mobility is studied for samples both with and without a surface gate. The obtained results indicate that background impurities and an inhomogeneity of the electric field coming from the surface govern the mobility in a low-electron-density region and that the interface inhomogeneity becomes important at a high electron density.