Evidence of valence band perturbations in GaAsN/GaAs(001): A combined variable-angle spectroscopic ellipsometry and modulated photoreflectance investigation

TL;DR

This study investigates how nitrogen incorporation in GaAsN alloys affects both conduction and valence bands using spectroscopic ellipsometry and photoreflectance, revealing valence band perturbations.

Contribution

It provides the first combined analysis of dielectric function and oscillator strengths to show valence band effects in GaAsN alloys.

Findings

Oscillator strength of E_ transition increases with nitrogen content

Both E+ and E+Delta(so) transitions become stronger as N increases

Valence band perturbations are evidenced by increased oscillator strengths

Abstract

The contribution of the fundamental gap E_ as well as those of the E_ + Delta(so) and E+ transitions to the dielectric function of GaAs1-xNx alloys near the band edge were determined from variable-angle spectroscopic ellipsometry and modulated photoreflectance spectroscopy analyses. The oscillator strength of the E_ optical transition increases weakly with nitrogen incorporation. The two experimental techniques independently reveal that not only the oscillator strength of the E+ transition but also that of E_ + Delta(so) become larger compared to that of the fundamental gap as the N content increases. Since the same conduction band is involved in both the E_ transition and its split-off replica, these results reveal that adding nitrogen in GaAs1-xNx alloys affects not only the conduction but also the valence bands.