Strain-enhanced luminescence from biaxially strained Ge light-emitting diodes on GeOI substrates

Due to the lack of efficient light sources compatible with complementary metal oxide semiconductor technology, the development of silicon-based photonic integrated circuits has been restricted. Germanium (Ge), with its small bandgap difference between the direct and indirect valleys, becomes a promising candidate for light emission when tensile strain is applied to modify its band structure. However, achieving high and uniform strain in electrically active devices remains a challenge. In this work, we present a biaxially tensile strained Ge light-emitting diode with a vertical p-i-n junction, fabricated on a germanium-on-insulator substrate. The energy difference between the Γ valley and the L valley is further reduced by introducing a biaxial tensile strain of ∼0.77% through the microbridge structure. A 1.7-fold enhancement is observed in the direct bandgap photoluminescence intensity at room temperature. Furthermore, the peak intensity of direct bandgap electroluminescence increases threefold at 400 K compared to room temperature. These results demonstrate the potential of biaxially strained Ge for efficient, Si-compatible light sources, advancing the integration of group-IV materials in silicon photonics.