Atomistic tight binding study of quantum confined Stark effect in GaBi _x As_1−x /GaAs quantum wells

Abstract

Recently, there has been tremendous research interest in novel bismide semiconductor materials (such as GaBixAs1−x) for wavelength-engineered, low-loss optoelectronic devices. We report a study of the quantum confined Stark effect (QCSE) computed for GaBixAs1−x/GaAs quantum well (QW) structures based on large-scale atomistic tight-binding calculations. A comprehensive investigation of the QCSE as a function of the applied electric field orientations and the QW Bi fractions reveals unconventional character of the Stark shift at low Bi compositions (x=3.125%). This atypical QCSE is attributed to a strong confinement of the ground-state hole wave functions due to the presence of Bi clusters. At technologically-relevant large Bi fractions (≥ 10%), the impact of Bi clustering on the electronic structure is found to be weak, leading to a quadratic Stark shift of the ground-state transition wavelength, similar to previously observed in other conventional III-V materials. Our results provide useful insights for the understanding of the electric field dependence of the electronic and optical properties of GaBixAs1−x/GaAs QWs, and will be important for the design of devices in the optoelectronics and spintronics areas of research.

Towards low-loss telecom-wavelength photonic devices by designing GaBixAs1−x/GaAs core–shell nanowires

“…Finally, we wish to point out that the spatial confinements of the highest hole wave functions in the investigated nanowires are in stark contrast with the quantum well structures previously studied in the literature [62]. At the large Bi fractions (x ≥10%), the impact of the random alloy configurations was found to becomes weak and the confinement of the hole wave functions became quite uniform in the quantum well nanostructures.…”

“…(d) The threedimensional visualisations of wave function charge densities are shown for the lowest electron (shown as red color distribution) and the highest hole (shown as cyan color distribution) states. The green cylinders are plotted to indicate the boundaries of the core and shell regions.nanowires for the proposed optimised light absorption will require further experimental progress in the coming years, however, it is anticipated that the near term devices may be based on relatively low Bi fractions (5-15%) accompanied by larger ρ D , which could be suitable for applications where a large carrier separation is desirable.Finally, we wish to point out that the spatial confinements of the highest hole wave functions in the investigated nanowires are in stark contrast with the quantum well structures previously studied in the literature [62]. At the large Bi fractions (x ≥10%), the impact of the random alloy configurations was found to becomes weak and the confinement of the hole wave functions became quite uniform in the quantum well nanostructures.…”