RECOMBINATION AND THERMAL EMISSION OF EXCITONS IN SHALLOW CDTE CD(1-X)MG(X)TE QUANTUM-WELLS/

The recombination dynamics of excitons in shallow CdTe/Cd1-xMgxTe mult iple single quantum wells has been investigated. In the low-temperatur e regime (T less than or equal to 50 K), radiative recombination domin ates the decay of the excitonic luminescence. The low-temperature life time as well as the increase of the lifetime with temperature are stro ngly well-width dependent, due to the correlation between the exciton binding energy and the radiative Lifetime. At high temperatures, a dec rease of the lifetime and of the photoluminescence intensity is observ ed that depends on the well width and the Mg content in the barrier. B y analyzing transient photoluminescence spectra, carrier capture and t hermal emission were studied. Within the first picoseconds after the e xcitation, the carriers are distributed between the quantum wells by a fast capture process. Subsequently, thermal emission reduces the popu lation in shallow quantum wells inducing a transfer between the quantu m wells via barrier states.