Capacitively induced high mobility two-dimensional electron gas in undoped Si∕Si1−xGex heterostructures with atomic-layer-deposited dielectric

Abstract

The authors demonstrate that a high mobility two-dimensional electron gas can be capacitively induced in an undoped Si∕Si1−xGex heterostructure using atomic-layer-deposited Al2O3 as the dielectric. The density is tuned up to 4.2×1011∕cm2, limited by the gate leakage current. The mobility increases with the density rapidly and reaches 5.5×104cm2∕Vs at the highest density. The observation of well developed quantum Hall states and two-dimensional metal-insulator transition shows that the devices are suitable for two-dimensional electron physics studies.