Optical Direct and Indirect Excitation of Er 3+ Ions in Silicon
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OPTICAL DIRECT AND INDIRECT EXCITATION OF Er 3 + IONS IN SILICON
A. Majima*,
S. Uekusa*,
K. Ootake*,
K. Abe*,
and M. Kumagai**
*Meiji University, Kawasaki, Kanagawa, 214 Japan. **Kanagawa High-Technology Foundation, Kawasaki, Japan.
Kanagawa,
214
ABSTRACT Optical direct and indirect excitation of erbium (Er) ions in silicon 3 substrates was performed in order to investigate the high efficiency of Er +related 1.541.m emission (4113/2--->4115/2) for direct excitation that is not concerned with the indirect band gap and low quantum efficiency of a Si host. The samples were prepared by ion-implantation or thermal diffusion methods. In each sample, photoluminescence (PL) showed the peaks 3 originating from 4 113/2--4 4 115/2 of Er + ions. In Er thermally diffused samples, optical excitation for energy level 4111/2 of Er 3+ ions was successfully effected by photoluminescence excitation spectroscopy (PLE). The PLE spectra consisted six peaks (963. lnm, 965.Onm, 976.lnm, 978.9nm and 980.9nm) which were caused by direct excitation (4115/2--->4111/2) of Er 3 ÷ ions. The emission directly excited is about 2 times more intense than the indirectly excited emission. The six peaks originating from the splitting of the 4111/2 levels meant that Er 3 + ions were in the sites of noncubic symmetry. The samples prepared by Er ion-implantation did not show the effect.
INTRODUCTION A emission in Si is weak because of the its indirect band gap, and the
applications of Si have been limited to electrical devices and light absorbing devices. With development of optoelectronic integrated circuits (OEICs), it has been necessary to fabricate light emitting devices in/on Si substrate. In recent years an increasing amount of research has been focused on the realization of III-V/Si-structure OEICs. However, for systems of GaAs light-emitting devices on Si , there is a high lattice mismatch of about 4%. On the other hand, electroluminescence and photoluminescence from rareearth ions incorporated into III-V compound semiconductors and silicon have been studied because of the sharp and temperature-independent emission due to intra-4f-shell transition of rare-earth ion [1-8]. Especially the 1.541.m luminescence peak from Er 3 + ions have been attracted increasing attention because the wavelength is corresponding to minimum absorption of silica fibers. For the Si:Er system, Er 3 ÷-related 1.54 jim emission is weak, and it is hard to observe the emission at room temperature until now. However, It was reported that the Er doped amorphous silicon prepared from rf-sputtering technique showed Er 3 +-related emission at room temperature [1]. Recent studies revealed that impurities (B, C, 0, N and F) codoped in Si:Er enhance Er 3 +-related emission [2]. This is due to the fact
Mat. Res. Soc. Symp. Proc. Vol. 301. ©1993 Materials Research Society
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that these impurities increase the number of optically activated Er 3 + ions. In this work, Er 3 + ions were excited by direct and indirect excitation in order to investigate the Er 3 +-related emis
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