High-Mobility Two-Dimensional Electron Gas from Delta-Doped Asymmetric AlxGa1-xAs/GaAs/AlyGa1-yAs Quantum Wells

Abstract

A new delta (δ)-doped asymmetric Al _x Ga_1-x As/GaAs/Al _y Ga_1-y As quantum well structure is designed and grown by molecular beam epitaxy which provides a high-mobility two-dimensional electron gas with µ = 3.2×10⁵ cm²/Vs at 5 K. The key feature of the new structure is that no bound states for electrons are found in the asymmetric well if the width is smaller than the critical value. The undesired persistent photoconductivity effect due to deep donors in n-type Al _x Ga_1-x As: Si does not exist in the structure. Important for high transconductances in field-effect transistor is the narrow spacing between the two-dimensional electron gas and the crystal surface.