Spectroscopic Ellipsometry Study of Cd(1-x)Mn(x)Te/Cd(1-y)Mn(y)Te Superlattices

We studied, by means of spectroscopic ellipsometry, dilute magnetic Cd(1–x)Mn(x)Te/CdTe semiconductor superlattices and Cd1–xMnxTe thin films grown by molecular beam epitaxy. In superlattices, the pseudodielectric function measured by ellipsometry shows specific features related to the excitonic transition between quantized minibands. In thin films, ellipsometry allows the clear identification of the energy gap. Additionally, critical point transitions are observable both in the spectra of the superlattices and films. Photoluminescence experiments have also been measured in order to evidence the fundamental interminiband excitonic transitions in superlattices and the energy gap in thin films, respectively. The electronic structure of the superlattices has been calculated in the framework of the envelope function approximation and compared with the experimental spectra. Ellipsometry appears to be a suitable technique to monitor the molecular beam epitaxy growth, ultimately also in situ, of dilute magnetic low-dimensional semiconductor systems.