Mechanism of excitation of erbium electroluminescence in amorphous silicon

We have studied electroluminescence (EL) in the amorphous silicon-based erb ium-doped structures in the temperature range 77-300 K. The EL intensity at the wavelength of 1.54 mu m corresponding to a radiative transition in the internal 4f-shell of the Er3+ ion is low at 77 K but sharply increases sta rting from 220 K and exhibits a maximum near the room temperature. Measurem ents of the resistance of the electroluminescent structure as a function of temperature performed in parallel with the measurements of the EL intensit y demonstrated a correlation in behavior of these two quantities: a pronoun ced decrease of the resistance occurs at the same temperature where the EL intensity starts to rise. Our results can be explained by the excitation of erbium ions via an Auger process which involves the capture of conduction electrons by neutral dangling bonds (D-0) defects located close to erbium i ons and thermally activated tunnel emission of electrons from deep donors t o the conduction band that keeps the stationary current through the structu re. A theoretical model proposed explains consistently all of our experimen tal data. (C) 1999 Elsevier Science B.V, All rights reserved.