We report on high speed operation of a Ge/SiGe multiple quantum well (MQW) electro-absorption modulator in a waveguide configuration. 23 GHz bandwidth is experimentally demonstrated from a 3 µm wide and 90 µm long Ge/SiGe MQW waveguide. The modulator exhibits a high extinction ratio of more than 10 dB over a wide spectral range. Moreover with a swing voltage of 1 V between 3 and 4 V, an extinction ratio as high as 9 dB can be obtained with a corresponding estimated energy consumption of 108 fJ per bit. This demonstrates the potentiality of Ge/SiGe MQWs as a building block of silicon compatible photonic integrated circuits for short distance energy efficient optical interconnections.

We investigate the room-temperature quantum-confined Stark effect in Ge/SiGe multiple quantum wells (MQWs) grown by low-energy plasma-enhanced chemical vapor deposition. The active region is embedded in a p-i-n diode, and absorption spectra at different reverse bias voltages are obtained from optical transmission, photocurrent, and differential transmission measurements. The measurements provide accurate values of the fraction of light absorbed per well of the Ge/SiGe MQWs. Both Stark shift and reduction of exciton absorption peak are observed. Differential transmission indicates that there is no thermal contribution to these effects.

We report room temperature direct gap electroluminescence (EL) from a Ge/Si0.15Ge0.85 multiple quantum well (MQW) waveguide. The excitonic direct gap transition and the dependence of the EL intensity on the injection currents and temperature are clearly observed. EL from the Ge/SiGe MQWs is shown to have a transverse-electric polarization. These results demonstrate the strong potential of the Ge/Si0.15Ge0.85 MQWs in terms of the realization of a monolithically integrated light source on the Si platform.