A comparative study of donor formation in dysprosium, holmium, and erbium implanted silicon

Formation of donor centers in Czochralski grown silicon doped with dysprosi um, holmium. and erbium is discussed. Donor states of three kinds are intro duced in the implanted layers after annealing at T = 700 degrees C. Shallow donor states with ionization energies between 20 and 40 meV are attributed to oxygen -related thermal donors. Other donor centers in the energy range of E-c - (60...70) meV and E-c - (100... 120) meV appear to be dependent o n dopants. After a 900 degrees C anneal strong changes in the donor formati on are observed only in silicon doped with erbium. Instead of donors at E-c - (118 +/- 5) meV, new donor centres at E-c - (145 +/- 5) meV are formed. Reportedly, the latter ones are involved in the excitation process of the E r3+ ions with a characteristic luminescence line at approximate to 1.54 mu m. (C) 1999 Elsevier Science B.V. All rights reserved.