Band offsets and excitons in CdTe/(Cd,Mn)Te quantum wells

S. K. Chang, A. V. Nurmikko, J. W. Wu, L. A. Kolodziejski, R. L. Gunshor

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The question of band offsets and details of exciton binding are investigated in the CdTe/(Cd,Mn)Te heterostructure in the quantum-well limit. Photoluminescence excitation spectroscopy in external magnetic fields is used to vary the quantum-well potential depths in this moderately strained (0.6% lattice mismatch) diluted magnetic semiconductor heterostructure. Large Zeeman splittings are observed at all the principal quantum-well transitions and at the barrier band gap for a structure of CdTe well thicknesses of 50 A and a Mn-ion concentration in the barrier layer of x=0.24. A variational theory is developed for excitons, especially accounting for the possibility of a small valence-band offset. Good agreement between theory and experiment is obtained and a band offset of 25 meV is deduced for the heavy-hole valence band, corresponding to a conduction- to valence-band offset ratio of about 14:1. This implies that the valence-band offset in a hypothetical strain-free case is virtually zero. The accuracy of the offset determination is believed to be better than 10 meV. Exciton binding energies are found to vary appreciably in the magnetic field; the zero-field value is approximately twice that for bulk CdTe.

Original languageEnglish
Pages (from-to)1191-1198
Number of pages8
JournalPhysical Review B-Condensed Matter
Issue number3
Publication statusPublished - 1988

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics


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