Landau levels and shallow donor states in GaAs/AlGaAs multiple quantum wells at mega-gauss magnetic fields

TL;DR

This study investigates Landau levels and shallow donor states in GaAs/AlGaAs quantum wells under ultra-high magnetic fields up to 140 T, combining magneto-optical measurements with advanced theoretical modeling to interpret the electronic states.

Contribution

It provides a comprehensive analysis of magneto-donor states and Landau levels at mega-gauss magnetic fields using a combined experimental and theoretical approach, extending previous lower-field studies.

Findings

Magneto-optical transitions are consistent with the combined free-electron and magneto-donor state model.

Magneto-donor energies are accurately calculated considering band nonparabolicity.

Results confirm the applicability of existing models at ultra-high magnetic fields.

Abstract

Landau levels and shallow donor states in multiple GaAs/AlGaAs quantum wells (MQWs) are investigated by means of the cyclotron resonance at mega-gauss magnetic fields. Measurements of magneto-optical transitions were performed in pulsed fields up to 140 T and temperatures from 6 to 300 K. The $14\times14$ \textbf{P}$\cdot$\textbf{p} band model for GaAs is used to interpret free-electron transitions in a magnetic field. Temperature behavior of the observed resonant structure indicates, in addition to the free-electron Landau states, contributions of magneto-donor states in the GaAs wells and possibly in the AlGaAs barriers. The magneto-donor energies are calculated using a variational procedure suitable for high magnetic fields and accounting for conduction band nonparabolicity in GaAs. It is shown that the above states, including their spin splitting, allow one to interpret the observed magneto-optical transitions in MQWs in the middle infrared region. Our experimental and theoretical results at very high magnetic fields are consistent with the picture used previously for GaAs/AlGaAs MQWs at lower magnetic fields.