High-mobility variable-density two-dimensional electron gas in inverted GaAs-AlGaAs heterojunctions

Inverted heterointerfaces (GaAs on AlGaAs), which are basic constituents of all quantum wells and superlattices, have been significantly improved using electron diffraction and a refined molecular beam epitaxy growth procedure. Utilizing them in a novel structure allowed the variation of the electron density over a wide range, with peak mobilities of 4×105 cm2/V s. The continuously variable electron density allowed comparison to a theoretical analysis of the low-temperature scattering mechanisms, and their relation to the growth process, establishing the importance of interface charges and roughness. High-mobility samples were used to observe the quantum Hall effect with varying carrier concentrations in a single structure.