OPTICAL INVESTIGATION OF CONFINEMENT AND STRAIN EFFECTS IN CDTE (CDMG)TE QUANTUM-WELLS/

We present optical investigations on CdTe/(CdMg)Te single quantum well s (QWs) and demonstrate the high structural quality of the pseudomorph ic grown QWs structure which shows high photoluminescence efficiency u p to room temperature. Due to the large band-gap difference between Cd Te and Cd0.51Mg0.49Te of more than 0.8 eV remarkable strong confinemen t effects are observable. A strong enhancement of the exciton binding energies is found by decreasing well width. In the 50-angstrom-wide QW the binding energy is more than two times larger compared with that o f bulk CdTe. In addition, a strong functional dependence of the locali zation energy of donor bound excitons on the well thickness is found. A valence-band offset of 30% in the strain-free limit is determined fr om the energy difference between heavy- and light-hole excitons which is consistent with the strong blue shift of exciton energies by decrea sing well widths and the observed effective electron-hole confinement.