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

Wide quantum dots were fabricated from multiple quantum-well (MQW) structures based on Zn_1-xMn_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 σ⁺ transition is virtually independent of magnetic field whilst the hh exciton is field-dependent. Thus, at fields of 1-2 T, the hh exciton σ⁺ 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-xMn_xTe/ZnTe.