SUPPRESSION OF GROUND-STATE OPTICAL RECOMBINATION IN THE QUANTUM HALLREGIME

The time evolution of optical recombination in the two-dimensional ele ctron gas in GaAs/(Ga,Al)As heterostructures shows an anomalous increa se at the Landau-level filling factor nu = 1. Here we find that the ra diative recombination rate is slowed by an order of magnitude and is c ommensurate with the quantum Hall effect. The inhibited electron-hole recombination is caused by localization and changes in the screening r esponse of the electron gas, which leads to reduced electron-hole over lap and broadening of the density of states. These mechanisms are also manifest in a large increase in hole relaxation time at nu = 1.