Strain effects in Cd1-xMnxTe-CdTe superlattices

Quantum-size effects and strain effects have been calculated for the CdMnTe-CdTe superlattice. Unlike previous theories dealing with materials grown in the [100] direction, this work applies to CdMnTe-CdTe superlattices oriented in the [111] direction. A Kronig-Penney analysis is used to obtain the quantized conduction-band energies. Pikus-Bir deformation theory is employed to calculate the strain-induced splitting of the heavy and light-hole valence bands. Excitation luminescence spectra obtained for several CdMnTe-CdTe superlattices exhibit sharp peaks which correspond to heavy and light-hole excitonic transitions from the quantized conduction-band states. Observed transition energies from the n = 1 conduction band state are used with the theory to obtain the heavy and light-hold exciton binding energies for the supperlattices. An increase in binding energies over the values for bulk CdTe is obtained and is attributed to the 2D nature of the quantum wells and possibly strain-induced distortion of the valence bands. The calculated transition energies from higher level (n = 2, 3,.) conduction-band states agree closely with the experimental data.