Erbium-doped silicon epilayers grown by liquid-phase epitaxy

Liquid-phase epitaxy from an Si-In-Er solution at an average temperature of 950 degrees C has been used to grow 2- 4 mu m thick epilayers of erbium-doped silicon onto CZ and FZ silicon substrates in an oxygen-free hydrogen atmosphere. Most of the samples grown on CZ substrates presented detectable, but feeble photoluminescence at 2. K in the spectral range of emission of the Er3+ manifold at 0.8 eV. However, some of the samples presented intense photoluminescence characterized by two bands at 0.807 (at 10 K) and 0.873 eV, of which the first falls almost at the same energy of the Er3+ line, but whose intensity presents a quite remarkable persistence up to 250 Ii. From the energy position of the two bands, from their temperature dependence and from the levels found by deep level transient spectroscopy measurements, associated to TEM examinations, it was possible to attribute these bands, labelled D1 and D2, to dislocation luminescence. It will be shown in this paper that the presence of erbium enhances the D1 luminescence, possibly due to the fact that in these samples erbium is gettered at dislocations in an Er-O local configuration, as it results from EXAFS measurements. Apparently, also, a competition occurs with the Er-induced radiative recombination at dislocations, which is a fast process, and the indirect excitation of the Er manifold, which is the predominant process in dislocation-free materials. (C) 1999 Elsevier Science B.V. All rights reserved.