Exciton formation rate in quantum wells from a direct comparison between free‐carrier and exciton contributions to time resolved luminescence

We present the results of a detailed time resolved luminescence study carried on a very high quality InGaAs quantum well sample. We clearly separate the contributions to the total intensity at the energy of the exciton and at the band by performing experiments with the proper spectral resolution and sensitivity, allowing to keep the observation of these two separate contributions over a broad range of times and densities. This enables us to access to the exciton formation rate over a broad range of pair densities. We also evidence the dominant contribution of excitons to the luminescence signal even when their population is small, and the absence of thermal equilibrium between excitons and free carriers at low enough densities. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)