Valence band offset in semimagnetic CdTe/(CdMn)To quantum wells

Abstract

We present a comparative study of two different spectroscopic techniques in order to determine the valence band offset in CdTe/(CdMn)Te quantum wells. On the one hand the energy difference between heavy- and light-hole excitons as a function of the heavy-hole transition energy is employed. We determine a valence band offset of Qv=0.30 for CdTe/(CdMn)Te, which is valid in the whole range of investigated Mn-contents up to x=0.27. An alternative determination of the valence band potential height is based on the tuning of potential heights due to external magnetic fields in semimagnetic quantum wells. Analysing the Zeeman splitting of the heavy-hole exciton in CdTe/(CdMn)Te quantum wells with different Mn-contents, we demonstrate a significant decrease of the valence band offset with increasing Mn-content in the barrier. From the comparison of the two different spectroscopic methodes including published data, we conclude that the valence band offset derived from the Zeeman splitting in CdTe/(CdMn)Te quantum wells with high Mn-content is strongly underestimated.