Magneto-photoluminescence studies of Zn_{1-x}Mn_xTe/ZnTe multiple quantum-well and quantum dot structures

TL;DR

This study investigates the photoluminescence properties of Zn_{1-x}Mn_xTe/ZnTe quantum well and quantum dot structures under magnetic fields, revealing strain effects and exciton behavior differences.

Contribution

It provides a detailed analysis of strain-induced shifts in exciton energies and identifies the dominant emission mechanisms in quantum wells and dots, with a new model for valence band offset.

Findings

Heavy-hole excitons dominate in MQWs.

Strain shifts light-hole excitons below heavy-hole excitons in quantum dots.

Magnetic field dependence varies between exciton types.

Abstract

Wide quantum dots were fabricated from multiple quantum well structures based on Zn_{1-x}Mn_xTe/ZnTe (x = 0.076) dilute magnetic semiconductors and were investigated via photoluminescence (PL) in a magnetic field. Calculations taking into account the strain in the two types of structure enabled the PL transitions to be identified and show that the dominant emission in the MQWs is from heavy-hole (hh) excitons whereas in the quantum dots, the removal of the strain in the barrier layers generates a large biaxial tensile strain in the quantum wells which shifts the light-hole (lh) exciton to lower energy than the hh exciton. The lh exciton sigma^+ transition is virtually independent of magnetic field whilst the hh exciton is field-dependent. Thus, at fields of 1 to 2 Tesla, the hh exciton sigma^+ transition again becomes the lowest energy transition of the quantum dots. These observations are described by a model with a chemical valence band offset of 30% for Zn_{1-x}Mn_xTe/ZnTe.