Bandgap narrowing in Mn doped GaAs probed by room-temperature photoluminescence

TL;DR

This study investigates how manganese doping affects the electronic band structure of GaAs using room-temperature photoluminescence and ellipsometry, revealing bandgap narrowing and valence-band shifts at low Mn concentrations.

Contribution

It provides experimental evidence of bandgap narrowing and valence-band shifts in Mn-doped GaAs, highlighting effects at very low Mn concentrations and confirming alloy formation.

Findings

Valence-band up-shift observed with increasing Mn content

Valence-band merges with impurity band at 0.6 at.% Mn

Full recrystallization and alloy formation confirmed

Abstract

The electronic band structure of the (Ga,Mn)As system has been one of the most intriguing problems in solid state physics over the past two decades. Determination of the band structure evolution with increasing Mn concentration is a key issue to understand the origin of ferromagnetism. Here we present room temperature photoluminescence and ellipsometry measurements of Ga_{100%-x}Mn_{x}As alloy. The up-shift of the valence-band is proven by the red shift of the room temperature near band gap emission from the Ga_{100%-x}Mn_{x}As alloy with increasing Mn content. It is shown that even a doping by 0.02 at.% of Mn affects the valence-band edge and it merges with the impurity band for a Mn concentration as low as 0.6 at.%. Both X-ray diffraction pattern and high resolution cross-sectional TEM images confirmed full recrystallization of the implanted layer and GaMnAs alloy formation.