DETERMINATION OF THE BAND-OFFSET IN SEMIMAGNETIC CDTE CD1-XMNXTE QUANTUM-WELLS A COMPARISON OF 2 METHODS

We present a comparative study of two different spectroscopic techniqu es in Order to determine the valence band offset in CdTe/Cd1-xMnxTe qu antum wells. The energy difference between heavy- and light-hole excit ons as a function of the heavy-hole transition energy is known as a se nsitive tool for the determination of the valence band potential heigh t. In the present study we have employed this technique to CdTe/Cd1-xM nTe quantum wells. A valence band offset around Q(upsilon) = 0.30 is d etermined, which is found to be valid in the whole range of investigat ed Mn contents up to x = 0.27. In semimagnetic quantum wells the tunin g of potential heights in external magnetic fields offers the possibil ity to evaluate the valence band offset. This technique has been widel y employed to CdTe/Cd1-xMnxTe, but no consensus has been reached yet. We have analyzed the Zeeman splitting of the heavy-hole exciton in CdT e/Cd1-xMnxTe quantum wells with different Mn contents. Using the valen ce band offset as an adjustable parameter, a smaller valence band offs et is determined for quantum wells with higher Mn content in the barri er. The published data derived from magneto-optical experiments show t his 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 i s explained by an enhanced paramagnetic contribution arising at the he terointerface of semimagnetic quantum wells.