Abstract

Localized exciton energy relaxation in three undoped lattice mismatched Al_0.35Ga_0.65As/GaAs_1–yP_y strained quantum wells (QWs) has been investigated by using picosecond time-resolved photoluminescence (PL) spectroscopy. The well widths (L_Z) for two QWs with y = 0.05 are 121 Å (QW-A) and 79 Å (QW-B). Another QW (QW-C) is L_Z = 121 Å with y = 0.08. QW-C is more strained. For these structures, the lowest energy excitons are degenerate exciton, heavy exciton, and light exciton in QW-A, B, and C, respectively. We have evaluated the time varying average exciton energies <E(t)> for the QWs from the time-resolved PL spectra. The <E(t)> decreased exponentially with time. Using the exciton masses and exciton deformation potentials (DP) determined by linearly interpolating the values for GaAs and GaP, we have obtained excellent agreement in QW-A and B between <E(t)> data and the theoretical curves. The relaxation rate is confirmed to be proportional to the square of the product of exciton mass and DP and to be inversely proportional to L_Z. For QW-C, the energy relaxation rate is between the light and the heavy exciton relaxation rate. This indicates that the exciton in QW-C relaxes because of not only acoustic DP interaction but also because of other scattering mechanisms.

© 1992 Optical Society of America