MULTIPLE-PHONON RELAXATION IN GAAS-ALGAAS QUANTUM-WELL DOTS

We report resonant Raman scattering (RRS) and ''hot'' exciton luminescence (HEL) from dry etched GaAs-AlGaAs quantum dots in which quantum confinement effects have been found with decreasing dot sizes. Up to fourth-order multiphonon processes have also been observed for the first, time via photoluminescence and photoluminescence excitation in quantum dots. These results are direct evidence of the bottleneck effect. Hot carriers are maintained due to the slowed-down electron-phonon scattering in one- and zero-dimensional semiconductors. The competition between resonant relaxation via LO phonons and sidewall nonradiative recombination results in stronger multiphonon processes with increasing quantum confinement. Furthermore, lateral patterning of quantum wells strongly localizes excitons in three-dimensional quantum confinement regime. The observation of RRS and HEL up to high temperature demonstrates the high stability of localized excitons.