Strained Germanium Microbridge LED Array Using Elliptical Windows Etching

As a candidate for a group IV luminescent material, germanium (Ge) has broad development prospects in silicon-based light sources. Introducing tensile strain into Ge to change its band structure and improve its electroluminescence efficiency is a key research focus for silicon-based light sources. A strained Ge microbridge LED array using elliptical windows etching is presented in this paper. A significant amount of uniaxial tensile stress can be applied at the center of the bridge by using microbridge structures. The stress concentration at the corners of the microbridge can be eliminated by utilizing elliptical window etching. Simulation results show that a uniaxial tensile stress of 2.48 GPa was achieved in the central region of the Ge microbridge, resulting in a 2.4% uniaxial tensile strain, which narrowed the E_gΓ of Ge in the microbridge center to 0.629 eV. This resulted in an optimal electroluminescence conversion efficiency of 1.79% and a peak emission wavelength of 1838 nm. This work offers a pathway toward higher efficiency electroluminescence in group IV materials, as well as opens possibilities for silicon-based light sources compatible with CMOS process.