Lumocen effect, luminescence from molecular centers in solids

Electroluminescence in semiconductors is usually produced by recombination of electron-hole pairs either directly or via recombination centers. Another possible mechanism is the excitation of a center from its ground state to an excited state via direct electron impact which subsequently undergoes radiative decay. We report here on a new materials system in which the latter mechanism is dominantly operative and which shows some promise of utilization in electroluminescent devices. The system consists of rare-earth or transition metal ions which are incorporated as fluoride molecules in a II-VI compound semiconductor. Externally injected carriers are heated by an electric field to energies sufficient to put the ion in an excited state upon collision, much like a gas discharge. The creation of electron-hole pairs is not necessary or even desirable.