An infrared probe of the insulator-to-metal transition in GaMnAs and GaBeAs

TL;DR

This study uses infrared spectroscopy to investigate the insulator-to-metal transition in GaAs doped with magnetic (Mn) and non-magnetic (Be) acceptors, revealing distinct electronic behaviors and impurity state persistence across the transition.

Contribution

It provides new insights into the different electronic mechanisms in magnetic versus non-magnetic doped GaAs during the insulator-to-metal transition.

Findings

Impurity resonance persists across the IMT in GaMnAs.

Be-doped GaAs shows conventional metallic behavior above the IMT.

Magnetic and non-magnetic doping lead to different electronic transition signatures.

Abstract

We report infrared studies of the insulator-to-metal transition (IMT) in GaAs doped with either magnetic (Mn) or non-magnetic acceptors (Be). We observe a resonance with a natural assignment to impurity states in the insulating regime of Ga$_{1-x}$Mn$_x$As, which persists across the IMT to the highest doping (16%). Beyond the IMT boundary, behavior combining insulating and metallic trends also persists to the highest Mn doping. Be doped samples however, display conventional metallicity just above the critical IMT concentration, with features indicative of transport within the host valence band.