Determination of the band offset in semimagnetic CdTe/Cd1−xMnxTe quantum wells: A comparison of two methods

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Abstract
We present a comparative study of two different spectroscopic techniques in order to determine the valence band offset in CdTe/Cd1−x Mn x Te quantum wells. The energy difference between heavy‐ and light‐hole excitons as a function of the heavy‐hole transition energy is known as a sensitive tool for the determination of the valence band potential height. In the present study we have employed this technique to CdTe/Cd1−x Mn x Te quantum wells. A valence band offset around Q v =0.30 is determined, which is found to be valid in the whole range of investigated Mn contents up to x=0.27. In semimagnetic quantum wells the tuning of potential heights in external magnetic fields offers the possibility to evaluate the valence band offset. This technique has been widely employed to CdTe/Cd1−x Mn x Te, but no consensus has been reached yet. We have analyzed the Zeeman splitting of the heavy‐hole exciton in CdTe/Cd1−x Mn x Te quantum wells with different Mn contents. Using the valence band offset as an adjustable parameter, a smaller valence band offset is determined for quantum wells with higher Mn content in the barrier. The published data derived from magneto‐optical experiments show this behavior too. Only at low Mn contents (x<0.05) the results of both spectroscopic techniques coincide. The underestimation of the valence band offset derived from the Zeeman splitting at higher Mn contents is explained by an enhanced paramagnetic contribution arising at the heterointerface of semimagnetic quantum wells.