Kinetics of luminescence of isoelectronic rare-earth ions in III-V semiconductors

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Abstract
In this work we have developed a kinetics model of energy transfer from the host lattice to the localized core excited states of rare-earth isoelectronic structured traps (REI traps). The presence of low-lying empty core orbitals in rare-earth impurities introduces new excitation and recombination phenomena. To adequately describe the energy transfer to a REI trap, the buildup and decay kinetics of rare-earth luminescence, we consider six separate states of the REI impurity (unoccupied, electron occupied, electron occupied excited, exciton occupied, excited electron occupied, and excited exciton occupied). The energy-transfer processes occur through an Auger mechanism where the recombination energy of the bound electron with a free hole is transferred nonradiatively to the core states, or energy can be transferred from the bound exciton on a REI trap to the core states. If the initial and final states are not resonant (in both mechanisms), the energy mismatch must be accommodated by emission or absorption of phonons. Furthermore we discuss details of several quenching processes, which are incorporated into the kinetics equations. We derive two sets of differential equations for semi-insulating and n-type semiconductors governing the kinetics of rare-earth luminescence. Equations have been solved by a numerical method to derive the time dependence of the rise and decay kinetics as a function of excitation intensity. The numerically simulated luminescence rise and decay times show a good overall quantitative agreement with experimental data obtained for InP:Yb, over a wide range of generation rates.