The paper is a brief retrospective review of our contribution to the Si:Er problem in the last decade. It contains a description of the experimental facilities, results of the light emitting media (Si:Er and Si1-xGex:Er) research and device applications. The progress in the development of Si:Er-based light-emitting devices with a higher power yield and quantum efficiency is associated with the improvement of the optically active media (increase of optically active Er 3+ concentration, formation of optically active Er-containing complexes with higher excitation cross-section and minimization of Er 3+ nonradiative relaxation processes) and optimization of the light emitting devices design. In this contribution we focus on both approaches: i) we report a new optically active Er-containing complex radiating at 1.54 µm, a novel mechanism of sub-band-gap photo-excitation of erbium in silicon; ii) show possibilities to enhance the power yield of electroluminescent light emitting devices (LEDs) including LEDs radiating at room temperature at reverse and forward bias of the p-n junction, demonstrate a novel long-term optical memory effect on the basis of Si:Er light emitting structure with the active Si:Er layer placed within the depletion region, discuss the perspectives and progress in the development of laser-type structures on Si:Er basis; iii) develop an original sublimation variant of the MBE technique (SMBE) and demonstrate its capabilities for realizing light-emitting devices effectively radiating up to room temperature. STRUCTURE GROWTH AND CHARACTERIZATION