Optical Gain in Er-Doped Large-Bandgap Semiconductors GaN and ZnO
Abstract
Infrared emission from Er3+ ions embedded in GaN and in non-conventional Si-based nanomedia has been investigated in order to develop fundamental understanding of physical processes governing its efficiency. In particular, excitation mechanisms have been examined. For the GaN:Er, where direct and host-mediated excitations are possible, detailed information on the multiplicity and the excitation mechanism of optical centers has been obtained by combining information from emission and excitation spectroscopy. For Er-doped heterogeneous medium of Si-nanocrystals dispersed in SiO2, details of sensitization process were examined. We have shown, that the enhancement of excitation cross-section concerns only a very small percentage of Er dopants and has internal limits imposed by finite time duration of energy transfer processes. We conclude that optical gain is unlikely to be achieved in this system. For Si/Si:Er multinanolayer structures, in which preferential formation of a single type of high-symmetry Er center is realized, we have shown that creation of excitons is not strictly necessary for Er excitation. Further, we have identified a new excitation channel with photon energies close to Si bandgap. Since efficiency of this resonant process exceeds that of the band-to-band pumping, it opens new prospects for optical activation of Si:Er. We have also investigated the 2.7 gm emission from Er. For Si, we have theoretically modeled a possible excitation path and tested it experimentally. For GaN, we have looked for evidence of the 4I11/2 _ 4I13/2 transition both in emission at = 2.7 gm, and in the rise time of the 1.5 gm band. Since no conclusive results were obtained, we scrutinized in detail radiative and non-radiative recombinations for Er3+ ions in a truly insulating host.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2004
- Accession Number
- ADA524890
Entities
People
- Tom Gregorkiewicz
Organizations
- University of Amsterdam