Energy backtransfer and infrared photoresponse in erbium-doped silicon p-ndiodes

Temperature-dependent measurements of the photoluminescence (PL) intensity, PL lifetime, and infrared photocurrent, were performed on an erbium-implan ted silicon p-n junction in order to investigate the energy transfer proces ses between the silicon electronic system and the Er 4f energy levels. The device features excellent light trapping properties due to a textured front surface and a highly reflective rear surface. The PL intensity and PL life time measurements show weak temperature quenching of the erbium intra-4f tr ansition at 1.535 mu m for temperatures up to 150 K, attributed to Auger en ergy transfer to free carriers. For higher temperatures, much stronger quen ching is observed, which is attributed to an energy backtransfer process, i n which Er deexcites by generation of a bound exciton at an Er-related trap . Dissociation of this exciton leads to the generation of electron-hole pai rs that can be collected as a photocurrent. In addition, nonradiative recom bination takes place at the trap. It is shown for the first time that all t emperature-dependent data for PL intensity, PL lifetime, and photocurrent c an be described using a single model. By fitting all temperature-dependent data simultaneously, we are able to extract the numerical values of the par ameters that determine the (temperature-dependent) energy transfer rates in erbium-doped silicon. While the external quantum efficiency of the photocu rrent generation process is small (1.8x10(-6)) due to the small erbium abso rption cross section and the low erbium concentration, the conversion of Er excitations into free e-h pairs occurs with an efficiency of 70% at room t emperature. (C) 2000 American Institute of Physics. [S0021-8979(00)09620-1] .