Tunneling-assisted autoionization of the localized impurities in nanostructures

An impurity-related tunneling mechanism in nanostructures is proposed. It is the electron tunneling from the photopopulated impurity gap state to a neighboring well in which this state is energetically resonant with the host band (tunneling-assisted autoionization). Degradation of the impurity luminescence yield with kinetics being logarithmic with time is a fingerprint of the mechanism. The experimental evidence is given for CdF2/CaF2:Eu superlattices in which the characteristic Eu2+ 4f(6)5 double right arrow 4f(7) luminescence is quenched by light resonant with the 4f(7)double right arrow 4f(6)5d absorption. [S0163-1829(99)50304-4].