Magneto-optical study of heavy- and light-hole excitons in CdTe/(Cd,Mn)Te single quantum wells

Abstract

The authors report experimental and theoretical investigations of excitons in CdTe/Cd1-xMnxTe single quantum wells with high manganese content x=0.20 and various well widths. The Zeeman splitting of the excitonic transitions is measured by photoluminescence excitation in an external magnetic field up to 7.5 T. They have developed an extended model describing the Zeeman splitting of quantum well excitons, including the exchange interaction, the intrinsic g-factor of electron and hole and the Coulomb interaction in an external magnetic field. The calculation allows the interpretation of both light- and heavy-hole excitons. From the Zeeman splittings they deduce the natural valence band offset Qv in the strain-free limit. Due to the small; valence band offset, a magnetic field-induced type I to type II transition occurs for the heavy-hole state. They show that the main contribution to this transition comes from the excitonic effects, which nearly compensate for the large decrease of the confinement energy. In wide quantum wells with high manganese content they found an enhanced paramagnetic exchange interaction, which is discussed in terms of interface effects.