Optical Properties and Band Offset of PbTe/Pb1−xEuxTe Diluted Magnetic Semiconductor Multiquantum Wells Studied by Transmission and Photoconductivity Measurements

ABSTRACTFrom transmission experiments in the mid infrared region the optical interband transitions between electric subbands in the valence and conduction band of the PbTe wells embedded in Pb1−xEuxTe barriers (x = 2.6% to 3.0%) were determined and compared with calculations based on the envelope function approximation. The frequency dependence of the absorption constant α was calculated, taking the in-plane dispersion of the multiquantum well band structure into account. The frequency dependence of the refractive index n(ω) was derived from α(ω) using a Kramers-Kronig transformation and it exhibits several extrema which coincide with the onset of the various interband transitions. Experimentally the onset of these transitions was also observed in photoconductivity experiments. The changes in n(ω) are as large as 15 % and therefore important for the optical confinement in quantum well lasers grown with these materials.