Unintentional high density p-type modulation doping of a GaAs/AlAs core-multi-shell nanowire

TL;DR

This study demonstrates unintentional p-type doping in GaAs/AlAs nanowires through quantum well placement, revealing quantum confinement effects and high hole densities via magneto-optical and theoretical analyses.

Contribution

It introduces a novel doping method using quantum well placement to achieve p-type doping in GaAs/AlAs nanowires, supported by experimental and theoretical evidence.

Findings

Unintentional p-type doping achieved via quantum well placement.

Quantum confinement observed at the core/shell interface.

High 2D hole density indicated by magneto-optical signatures.

Abstract

Achieving significant doping in GaAs/AlAs core/shell nanowires (NWs) is of considerable technological importance but remains a challenge due to the amphoteric behavior of the dopant atoms. Here we show that placing a narrow GaAs quantum well in the AlAs shell effectively getters residual carbon acceptors leading to an \emph{unintentional} p-type doping. Magneto-optical studies of such a GaAs/AlAs core multi-shell NW reveal quantum confined emission. Theoretical calculations of NW electronic structure confirm quantum confinement of carriers at the core/shell interface due to the presence of ionized carbon acceptors in the 1~nm GaAs layer in the shell. Micro-photoluminescence in high magnetic field shows a clear signature of avoided crossings of the $n=0$ Landau level emission line with the $n=2$ Landau level TO phonon replica. The coupling is caused by the resonant hole-phonon interaction, which points to a large 2D hole density in the structure.