Kinetics of the Luminescence of Isoelectronic Rare-Earth Ions In III-V Semiconductors
- PDF / 367,204 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 37 Downloads / 166 Views
KINETICS OF THE LUMINESCENCE OF ISOELECTRONIC RARE-EARTH IONS IN HI-V SEMICONDUCTORS H .J. Lozykowski , Department of Electrical and Computer Engineering, and Condensed Matter & Surface Sciences Program Ohio University Athens, Ohio 45701 ABSTRACT In this work we have developed a model for the kinetics of the energy transfer from the host lattice to the localized core excited states of rare earth isoelectronic structured traps (REI-trap). We have derive a set of differential equations for semi-insulating semiconductor governing the kinetics of rare earth luminescence. The numerically simulated rise and decay times of luminescence show a good quantitative agreement with the experimental data obtained for InP:Yb, over a wide range of generation rates. INTRODUCTION The investigation of the luminescence properties of rare earth doped III-V is of great interest both from scientific and application points of view. The scientific interest is related to the uniqueness of optical and electrical properties of rare earth impurities in semiconductor hosts. Among the rare earth doped III-V semiconductors InP:Yb has been the most extensively studied [1-6]. In this paper we discuss only the structured isoelectronic traps (REI-trap) in III-V semiconductors introduced by RE" 3 ions replacing the element from column III. Furthermore, we develop a model of the luminescence kinetic that describes the energy transfer from the host to the REI-trap core states, and the recombination and quenching processes. Study of the rise and decay times at different excitation intensities, temperatures, can provide important information about the energy transfer and recombination (radiative, and non-radiative) processes. THEORETICAL FORMULATION An isoelectronic center can form bound states because of a short range central-cell potential. According to Thomas [7], the primary factors affecting the binding potential are the electronegativity and the size differences between the impurity and the host ion which it replaces. It is found experimentally that only very large atoms or very small atoms produce isoelectronic traps because they create large lattice distortion induced by the substitution. The above conclusion is supported by the fact that the atomic covalent radii (ionic RE" 3) for all rare earths are bigger than atomic radii of Ga and In that they are replacing. Pauling's electronegativity of rare earth elements is in the range of 1.1-1.25, and is smaller than Ga (1.81) and In (1.78) for which it substitutes. If the rare earth ions replace the element from column III in III-V compounds (that are isovalent concerning outer electrons of RE" ions) , they create isoelectronic traps. The rare earth isovalent traps that we can call isoelectronic "structured" impurities [8] possess unfilled 4fP core shells. The luminescence structure arises from intra-configurational f-f transitions in the core of the isoelectronic "structured" impurities. The striking feature of excitons bound to the isoelectronic traps is a long luminescence decay time, ranging from a
Data Loading...
