ELECTROLUMINESCENCE OF ERBIUM-DOPED SILICON

Recombination processes in rare-earth metals in semiconductors are a s pecial case due to the localized nature off electrons. Our work explor es in detail the radiative and nonradiative mechanisms of energy trans fer for erbium in silicon by investigating the temperature dependence of the intensity and the decay time of the photoluminescence of Er-rel ated centers in Si. We show that nonradiative energy back transfer fro m the excited Er 4f shell causes luminescence quenching below 200 K. W e study electroluminescence decay by applying different bias condition s during the decay. In a two-beam experiment the photoluminescence dec ay is monitored for different back,around-excitation laser powers. Cha nges in the decay time are strong evidence of the impurity Auger effec t as an efficient luminescence-quenching mechanism for Er in Si. A fas t initial luminescence decay component at high pumping powers is relat ed to quenching by excess carriers. The power dependence, the decay-ti me components, and the two-beam experiment are simulated by a set of r ate equations which involve the formation of excitons, a decrease of t he pumping efficiency by exciton Auger recombination, and a decrease o f radiative efficiency by the impurity Auger effect with free electron s. As a nonradiative deexcitation path competing with spontaneous emis sion, the impurity Auger effect decreases the excited-state lifetime o f Er in Si, and dominates the thermal quenching of luminescence in the temperature range from 4 to 100 K. We find that the decrease of emiss ion intensity above 100 K is caused by an unidentified second back-tra nsfer process.