Abstract

Using picosecond photoluminescence (PL), we have investigated the temperature dependence of the radiative lifetime of the negatively charged exciton (X⁻) in CdTe quantum wells (QWs). The X⁻ lifetime is found to increase from 70 ps at 2K up to about 200 ps at 30 K (see Fig 2) The increase is linear for temperatures bigger than 5K and reveals that X⁻ cannot be treated as a purely localised species. A linear increase is indeed predicted theoretically for delocalised X⁻ [1] In addition, the observed temperature behaviour demonstrates that unlike the donor bound exciton to which X⁻ has been previously compared, X⁻ radiative recombination can take place with a specific strongly k dependent selection rule The behaviour of X⁻ lifetime at the lower temperatures indicates the presence of a certain degree of localisation.

© 2000 IEEE