Low energy consumption and high speed germanium-based optoelectronic devices

Summary form only given. Silicon photonics has generated a strong interest in recent years, mainly for optical telecommunications and optical interconnects in microelectronic circuits. The main rationales of silicon photonics are the reduction of photonic system costs and the increase of the number of functionalities on the same integrated chip by combining photonics and electronics. In the group IV materials, germanium (Ge) has been identified as a promising material to cost-effectively enhance the performance of Si electronic and photonic integrated circuits (IC) [1,2]. In optics, despite being an indirect-gap semiconductor, Ge may play a key role enabling future chip scale optical interconnects to meet aggressive requirements in terms of power consumption, data density, speed, reliability and monolithic integration with silicon [2]. Strong light detection [3], modulation [4], and emission [5] capabilities around C and L telecommunication wavelength bands were shown using Ge direct-gap transitions of bulk Ge on Si. A new promising approach is to employ Ge/SiGe quantum wells (QWs). Indeed, such heterostructures were shown to further enhance light modulation based on quantum confined Stark effect (QCSE) using the direct-gap transition of Ge multiple quantum wells (MQW) embedded in a vertical p-i-n diode [6,7]. Light modulation, detection, and emission can be obtained with both Ge platforms.In this paper, we focus on the modulation performances and DC and high speed modulation performances of the Ge/SiGe MQW waveguide were investigated (figure 1a and 1b). The epitaxial growth of such Ge/SiGe stack was performed using LEPECVD. The Ge/SiGe MQW modulator exhibit a wide spectral range with an ER greater than 10 dB with only 12% overlap factor between the optical mode and the MQW. High speed modulation performance from Ge/SiGe MQWs was demonstrated up to 23 GHz in waveguide configuration at wavelengths around 1.4 μm. The working wavelength can be tuned according - o the QW configuration and modulation has been also demonstrated at 1.3μm. Recent results on waveguide integration will be presented and good performance of optical link will be reported.