RADIATIVE MECHANISMS IN ZNSE/ZNSSE SYMMETRICAL SUPERLATTICES

In this paper we report the results of an optical investigation of excitons in ZnSSe/ZnSe symmetric superlattices of well width ranging between 2 and 15 nm. A weak enhancement of the exciton binding energy is found, and the experimental values obtained from the photoluminescence excitation and absorption spectra are compared with the theoretical results of a variational calculation, in which a zero conduction band off-set is assumed. This assumption is supported by luminescence measurements under high hydrostatic pressure which give a conduction band off-set of about 6 meV. The effect of the strain has been included to properly reproduce the well witdh dependence of the heavy-hole and light-hole energies. Strong evidence of hot excitons generation is obtained from the oscillatory behaviour of the photoluminescence excitation spectra.