Incorporation and optical activation of erbium in silicon using molecular beam epitaxy

Abstract

Erbium is incorporated in crystalline silicon during molecular beam epitaxy on Si(100) at 600 degrees C, either in vacuum (6x10(-11) mbar) or in an O-2 ambient (4x10(-10) mbar). Strong Er segregation takes place during growth in vacuum, and only 23% of the total deposited Er is incorporated in the epitaxial layer. Films grown in an O-2 ambient show no Er segregation, and an Er concentration of 1.5x10(19) Er/cm(3) is incorporated in the crystal. The O content is 4x10(19) O/cm(3). Photoluminescence spectra taken at 10 K show the characteristic intra-4f luminescence of Er3+ at 1.54 mu m for both samples, grown with and without O-2. Differences found in the spectral shape indicate a difference in the local environment (presumably O coordination) of Er for the two cases. The O codoped film shows a 7 times higher Er luminescence peak intensity than the film grown without O. This is due to the higher incorporated Er concentration as well as an increased luminescence efficiency (lifetime without O: 0.33 ms, with O: 1.81 ms). The Er excitation efficiency is lower in the O codoped film than in the O-undoped film, which is attributed to the lower minority carrier lifetime in the O-doped material. Thermal annealing of the O codoped film at 1000 degrees C increases the excitation efficiency and hence the Er luminescence intensity. (C) 1996 American Institute of Physics.