Analysis of Biaxially Tensile Strained Ge/SiGe Multiple Quantum Wells for Electro-Absorption Modulators With Low Polarization Sensitivities

We analyze theoretically biaxially tensile strained Ge/Si0.18Ge0.82 multiple quantum wells (MQWs) for electro-absorption modulators with low polarization sensitivities. The difference between TE and TM polarized momentum matrix elements and absorption spectra are discussed. Our calculation indicates that polarization independent electroabsorption can be achieved by introducing 0.78% biaxial tensile strain in the buffer layer. The simulation results show that the maximum polarization independent absorption contrast ratio is 7.6 dB under 0 V/2 V operation at 1485 nm. The absorption contrast ratio is over 6 dB for both TE and TM polarizations with the wavelength ranging from 1467 to 1489 nm. The proposed scheme provides a promising approach to design highly efficient polarization independent Ge/SiGe MQWs electroabsorption modulators for on-chip optical transmission applications.