Resonant nonradiative energy transfer to erbium ions in amorphous hydrogenated silicon

The simultaneous study of absorption, luminescence, and ODMR spectra of erb ium doped a-Si:H and a SiCx:H alloy reveals that Er3+ ions are pumped by a resonant but nonradiative energy transfer from electron-hole pairs excited in the host. Direct optical pumping into absorption lines of Er3+ is not ob served. The emission of the Er3+ ions is strong and decreases only moderate ly from 77 K to room temperature. We propose an energy transfer by a Forste r mechanism, based on resonant dipole coupling, which quenches efficiently the luminescence of the host in the case of large erbium concentration. Res onance of electron-hole pairs to the excited state of the rare earth ion is achieved as electrons thermalize in tail states. (C) 1999 American Institu te of Physics. [S0021-8979(99)01714-4].