Conduction electrons localized by charged magneto-acceptors A$^{2-}$ in GaAs/GaAlAs quantum wells

TL;DR

This paper presents a variational theory for charged acceptor centers in GaAs/GaAlAs quantum wells, explaining how these centers localize conduction electrons and affect magneto-transport properties under high magnetic fields.

Contribution

It introduces a theoretical model describing the localization of multiple conduction electrons by charged acceptors in quantum wells, supported by experimental magneto-transport data.

Findings

Localized electrons are pushed to acceptor states at high magnetic fields.

A single negative acceptor can localize up to four conduction electrons.

Transport measurements show electrons are removed from conduction at high fields.

Abstract

A variational theory is presented of A$^{1-}$ and A$^{2-}$ centers, i.e. of a negative acceptor ion localizing one and two conduction electrons, respectively, in a GaAs/GaAlAs quantum well in the presence of a magnetic field parallel to the growth direction. A combined effect of the well and magnetic field confines conduction electrons to the proximity of the ion, resulting in discrete repulsive energies above the corresponding Landau levels. The theory is motivated by our experimental magneto-transport results which indicate that, in a heterostructure doped in the GaAs well with Be acceptors, one observes a boil-off effect in which the conduction electrons in the crossed-field configuration are pushed by the Hall electric field from the delocalized Landau states to the localized acceptor states and cease to conduct. A detailed analysis of the transport data shows that, at high magnetic fields, there are almost no conducting electrons left in the sample. It is concluded that one negative acceptor ion localizes up to four conduction electrons.