Strained Germanium LED with SiN Stressor and Microbridge based on Edge Stress Concentration

Tensile strain is a widely discussed mean which induces a direct bandgap in Ge for the realization of semiconductor optoelectronic devices compatible with Si microelectronics. In order to achieve greater stress, a Ge LED based on a microbridge structure is proposed in this paper. According to the edge stress concentration, two isosceles triangles with opposite apexes are etched on the Ge layer, creating ideal tensile strain at the apexes and facilitating the transition of Ge from an indirect bandgap semiconductor to a direct bandgap semiconductor. Furthermore, by introducing a SiN stressor between the Si substrate and the Ge layer, the tensile strain in the Ge layer is increased to 4.5%, thereby improving the optoelectronic properties of the Ge LED. Simulation results show that the optimized Ge LED exhibits the peak wavelength of 2190 nm and the maximum electrical-to-optical conversion efficiency of 2.15%.