Recent progress in efficient electroluminescence from silicon-based light emitting devices made by ion beam processing

This report reviews our recent progress on efficient electroluminescence (EL) from silicon pn junctions and rare earth doped metal-oxide-semiconductor light emitting devices (MOSLEDs) in the infrared to ultraviolet range [1-3]. Silicon pn diodes prepared by boron implantation have shown efficient band edge EL with a high efficiency above 0.15% at room temperature. A detailed study has shown that the anomalous increase of the EL intensity with increasing temperature comes from the release of free carriers by thermal ionization of bound excitons. They are trapped around locally enhanced p-type doping spikes formed by boron clustering at dislocations or fabricated by selective diffusion of boron through a patterned SiO2 mask layer.
Efficient EL from Er, Tb, Gd doped MOSLEDs at 1535, 541 and 316 nm with an high quantum efficiency of 14, 16.5, and 5 %, respectively, has been demonstrated in our MOSLEDs, which is comparable to that of III-V semiconductor devices. The EL properties of efficiency, decay time, and excitation cross-section were studied concerning cross relaxation at concentrations from 0.25 to 9% and clustering of rare earth dopants at annealing temperatures from 800 to 1100°C. Improving of the device stability is achieved by using double-stacked gate oxide layers, charge compensation and elimination of defects in SiO2 layers.
[1] J. M. Sun, W. Skorupa, T. Dekorsy , and M. Helm, J. Appl. Phys. 97, 123513 (2005)
[2] J. M. Sun, W. Skorupa, T. Dekorsy, and M. Helm, Appl. Phys. Lett. 85, 3387 (2004).
[3] J. M. Sun, T. Dekorsy, W. Skorupa, B. Schmidt, A. Mücklich, and M. Helm, Phys. Rev. B 70, 155316 (2004).