Well width dependence of the carrier life time in InGaAs/InP quantum wells

Investigations of the well width dependence of the radiative excitonic life time of InGaAs/InP quantum wells are reported, for well widths between 1 nm and 50 nm. The luminescence of the 1-1 transition of the quantum wells is detected via time resolved frequency up-conversion with the exciting Nd-YAG laser. In our experiments the time constants reveal an interesting phenomena with respect to the potential well thickness. For decreasing well widths we observe decreasing time constants of the excitonic recombination as has been observed for several other quantum well systems. But for well thicknesses below approximately 5 nm we find an increase of the life time with further decrease of the well widths. We explain the increase for small well widths by the reduced transition probability due to the delocalization of the envelope wavefunction of the electron in very small quantum wells.