Recombination and thermal emission of excitons in shallow CdTe/${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mg}}_{\mathit{x}}$Te quantum wells

The recombination dynamics of excitons in shallow CdTe/${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mg}}_{\mathit{x}}$Te multiple single quantum wells has been investigated. In the low-temperature regime (T≤50 K), radiative recombination dominates the decay of the excitonic luminescence. The low-temperature lifetime as well as the increase of the lifetime with temperature are strongly well-width dependent, due to the correlation between the exciton binding energy and the radiative lifetime. At high temperatures, a decrease of the lifetime and of the photoluminescence intensity is observed that depends on the well width and the Mg content in the barrier. By analyzing transient photoluminescence spectra, carrier capture and thermal emission were studied. Within the first picoseconds after the excitation, the carriers are distributed between the quantum wells by a fast capture process. Subsequently, thermal emission reduces the population in shallow quantum wells inducing a transfer between the quantum wells via barrier states. © 1996 The American Physical Society.