Exciton dynamics in ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs quantum-well heterostructures: Competition between capture and thermal emission

In a carefully selected set of strained ${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs quantum-well structures, we have studied experimentally and theoretically the competition between carrier collection from the GaAs barrier into the quantum wells and the inverse process, the thermal activated emission out of the wells into the barrier. Analyzing the temperature dependence of time-integrated photoluminescence measurements, we found excitons or electron-hole pairs to be emitted out of the well. A different sample geometry is used to demonstrate the importance of the barrier properties in the equilibrium of capture and thermal emission. Time-resolved experiments allow the determination of the typical time constants, namely the radiative and the nonradiative recombination lifetime as well as the emission time. A hydrodynamic model, including the diffusion in the barrier and the carrier capture and emission via LO phonons, was developed for a quantitative description of our experiments. With use of the experimental time constants, an excellent agreement between the time-integrated experiments and theory was found, giving evidence of the applicability of our model.