High-quality-factor room-temperature light-emitting diodes based on Ge self-assembled quantum dots are successfully fabricated by employing a lateral p-i-n diode structure and a modified L3-type photonic crystal nanocavity. Sharp resonant peaks with Q-factor larger than 800, corresponding to the cavity modes, are clearly observed in the electroluminescence spectrum under 50 A injected current, which exceeds the performances of previously reported devices [X. Xu et al.: Opt. Express 20 (2012) 14714]. The output power collected by a single-mode fiber is measured to be about 6 pW under 3 mA current, indicating a forward step towards silicon-based light sources for practical applications.

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