Optical Activity of Yb 3+ in MeV Ion-Implanted InP.
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OPTICAL ACTIVITY OF Yb 3* IN MeV ION-IMPLANTED InP.
S. Uekusa*, A. Majima*, H. Katsumata*, Y. Noyori*, and M. Kumagai** *Meiji University, Kawasaki, Kanagawa, 214 Japan **Kanagawa High-Technology Foundation, Kawasaki, Kanagawa, 214 Japan.
For the evaluation of an implanted layer, photoluminescence (PL) and photoluminescence excitation (PLE) measurements, which are nondestructive and sensitive methods for identifying impurities and 3 defects, were performed. Yb +-related sharp luminescence was observed at a wavelength of 1002nm, due to the transitions which occurred between the spin-orbit levels 2 F 5 / 2 --* 2F 7/2 of Yb 3 ÷ (4f 13 ). Most efficient 3 luminescence of Yb + was achieved at an excitation wavelength of around 880nm. The luminescence intensity of this peak (Yb 3 ÷) decreased with an increase in annealing temperature. Since the peak has not been observed for good samples in crystallinity, it may indicate that new, efficient energy transfer processes to rare-earth ions occur through the defect energy level. Especially, for the sample annealed at 600'C, Yb-related luminescence intensity excited by the photon energy below the band gap is about 3 times larger than that of excited by the photon energy above the band gap.
The optical behavior of rare-earth (RE)-doped III-V compound semiconductors, such as GaAs and InP, has been attractive because of its sharp and temperature-independent emission due to intra-4f-shell transition of RE . These features are very important in optoelectronic device applications, e.g., light-emitting diodes and laser diodes. Among the RE ions in Ill-V compounds, Yb-doped InP has been one of the most extensively studied materials in studies of the luminescence mechanism , because this material has two characteristic properties. For one thing an energy level scheme of the Yb-4f-shell is simple with only one excited state, for another Yb intra-4f-shell luminescence spectrum does not depend on the sample preparation methods: This luminescence spectrum has been observed in samples grown by liquid phase epitaxy (LPE) , metalorganic chemical vapor phase epitaxy (MOCVD) , molecular beam epitaxy (MBE) , as well as ion implanted samples . This suggests that the Yb atoms occupy only one type of lattice site in InP. Zeeman effect measurements have revealed that the Yb 3 ÷ in InP is in a site of Td symmetry, probably substituting indium . Whitney et al.  have observed that Yb forms an acceptor-like electron trap (AE trap) level at 30meV below the bottom of the conduction band. According to their proposed excitation model, the Yb-4f-shell is excited by an Auger-type transfer of energy from the recombining electronhole pair at the AE trap. On the other hand, Kasatkin et al.  and Kibrber et al.  have proposed that the Yb-4f-shell is excited by the energy released through the recombination of donor-acceptor pair, and either by direct capture of an exciton or impact excitation by hot carriers, respectively. Mat. Res. Soc. Symp. Proc. Vol. 3
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