Energy backtransfer and infrared photoresponse in erbium-doped silicon p-n diodes

Temperature-dependent measurements of the photoluminescence (PL) intensity, PL lifetime, and infrared photocurrent, were performed on an erbium-implanted silicon p–n junction in order to investigate the energy transfer processes 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 lifetime measurements show weak temperature quenching of the erbium intra-4f transition at 1.535 µm for temperatures up to 150 K, attributed to Auger energy transfer to free carriers. For higher temperatures, much stronger quenching is observed, which is attributed to an energy backtransfer process, in 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 pairs that can be collected as a photocurrent. In addition, nonradiative recombination takes place at the trap. It is shown for the first time that all temperature-dependent data for PL intensity, PL lifetime, and photocurrent can be described using a single model. By fitting all temperature-dependent data simultaneously, we are able to extract the numerical values of the parameters that determine the (temperature-dependent) energy transfer rates in erbium-doped silicon. While the external quantum efficiency of the photocurrent generation process is small (1.8×10^–6) due to the small erbium absorption 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 temperature.