INTRINSIC VERSUS EXTRINSIC EFFECTS IN EXCITATION DYNAMICS IN GaAs/GaAlAs SUPERLATTICES

We report studies of photoexcited carrier dynamics in GaAlAs/GaAs superlattices as a function of excitation power using optical technique. At low power, we observe a quadratic behavior of luminescence intensity, due to competition between electron-hole radiative recombination and trapping by defects. At higher power, a departure from this behavior is interpreted by a fast spatial expansion of the plasma. However, over the whole range, the measured decay time is mainly related to the trapping process