Modulation of the absorption coefficient at 1.3?μm in Ge/SiGe multiple quantum well heterostructures on silicon

We report modulation of the absorption coefficient at 1.3?μm in Ge/SiGe multiple quantum well heterostructures on silicon via the quantum-confined Stark effect. Strain engineering was exploited to increase the direct optical bandgap in the Ge quantum wells. We grew 9?nm-thick Ge quantum wells on a relaxed Si_0.22Ge_0.78 buffer and a contrast in the absorption coefficient of a factor of greater than 3.2 was achieved in the spectral range 1290–1315?nm.