Making use of a unique spin engineering possible in diluted magnetic semiconductors (DMS), we study magneto-optical properties of quantum wells with electrons as a function of their g factor (tuned widely from $g_{\mathrm{eff}}^{*}=-1.46$ to $+55).\mathrm{}$ The study is made on samples containing different densities of electrons in various spatial regions of a single structure. An unusual nonmonotonic behavior of the intensity of the trion-related transition is detected. We show that it reflects a reversal of the ordering of the spin-split electron levels with the magnetic field. We provide an experimental evidence that polarization properties of exciton-cyclotron resonances are governed by the spin splitting of the conduction band states only. A very strong band gap renormalization due to the presence of electrons is also determined in our quasi-two-dimensional DMS system.

• Received 18 November 1998

DOI:https://doi.org/10.1103/PhysRevB.59.R10437