Role of heavy ion co-implantation and thermal spikes on the development of dislocation loops in nanoengineered silicon light emitting diodes

Microstructural and electroluminescence measurements are carried out on boron implanted dislocation engineered silicon light emitting diodes (LEDs) co-implanted with the rare earth thulium to provide wavelength tuning in the infra-red. Silicon LEDs operating in the range from 1.1-1.35 mu m are fabricated by co-implantation of boron and thulium into n-type Si (100) wafers and subsequently rapid thermally annealed to activate the implants and to engineer the dislocation loop array that is crucial in allowing light emission. Ohmic contacts are applied to the p and n regions to form conventional p-n junction LEDs. Electroluminescence is obtained under normal forward biasing of the devices. The influence of implantation sequence (B or Tm first), ion dose, and the post-implantation annealing on the microstructure and electroluminescence from the devices is studied. A clear role of the heavy-ion Tm co-implant in significantly modifying the boron induced dislocation loop array distribution is demonstrated. We also identify the development of dislocation loops under thermal spikes upon heavy ion (Tm) implantation into Si. The results contribute to a better understanding of the basic processes involved in fabrication and functioning of co-implanted devices, toward achieving higher light emission efficiency. VC 2011 American Institute of Physics. [doi:10.1063/1.3614036]