Design and analysis of electro-absorption modulators with uniaxially stressed Ge/SiGe multiple quantum wells.

We propose and analyze theoretically electro-absorption modulators with uniaxially tensile strained Ge/Si0.19Ge0.81 multiple quantum wells (MQWs). The effects of uniaxial strain on band structures including Γ-valley and L-valley are discussed. The simulation results indicate that the absorption contrast of TE mode is improved by 3.1 dB while the TM mode absorption is reduced by two-thirds under 1.6% uniaxial tensile strain. Zero-biased electro-absorption modulators covering 1380-1550 nm wavelength can be achieved by introducing 0.18%-1.6% uniaxial tensile strain. Taking into account the TE-polarized mode excited usually in integrated waveguides, the proposed scheme provides a promising approach to design highly efficient Ge/SiGe MQWs electro-absorption modulators for on-chip optical transmission and cross-connect applications.