PICOSECOND MEASUREMENTS OF EXCITON TRAPPING IN SEMICONDUCTOR CLUSTERS

The formation of deep traps in 30 Å CdS semiconductor clusters has been time resolved using picosecond single-photon counting. The trapping rates, measured by the risetime of recombinate or emission, vary inversely with trap depth ranging from ≈ 30 ps above 500 nm to < 10 ps near the band edge. These rates depend very weakly on temperature, decreasing only two-fold from 100 to 4.8 K. The observed rates are most easily explained by rapid trapping into near band edge traps, followed by slower trap-to-trap diffusion until a deep trap is encountered. © 1990.