"Zero change" platform for monolithic back-end-of-line integration of phase change materials in silicon photonics

TL;DR

This paper presents a novel monolithic integration platform for phase change materials in silicon photonics, enabling low-power, reconfigurable optical devices without modifying existing photonic component libraries.

Contribution

The authors introduce a 'Zero change' back-end-of-line integration platform that allows seamless incorporation of phase change materials into silicon photonics without disrupting existing device fabrication.

Findings

Achieved monolithic integration of Sb2Se3 and Ge2Sb2Se4Te1 PCM with silicon photonics.

Reduced peak power consumption of optical switches by 48%.

Demonstrated >25dB rejection ratio and >7-bit intensity modulation in integrated devices.

Abstract

Monolithic integration of novel materials for unprecedented device functions without modifying the existing photonic component library is the key to advancing heterogeneous silicon photonic integrated circuits. To achieve this, the introduction of a silicon nitride etching stop layer at selective area, coupled with low-loss oxide trench to waveguide surface, enables the incorporation of various functional materials without disrupting the reliability of foundry-verified devices. As an illustration, two distinct chalcogenide phase change materials (PCM) with remarkable nonvolatile modulation capabilities, namely Sb2Se3 and Ge2Sb2Se4Te1, were monolithic back-end-of-line integrated into silicon photonics. The PCM enables compact phase and intensity tuning units with zero-static power consumption. Taking advantage of these building blocks, the phase error of a push-pull Mach-Zehnder interferometer optical switch could be trimmed by a nonvolatile phase shifter with a 48% peak power consumption reduction. Mirco-ring filters with a rejection ratio >25dB could be applied for >5-bit wavelength selective intensity modulation, and waveguide-based >7-bit intensity-modulation photonic attenuators could achieve >39dB broadband attenuation. The advanced "Zero change" back-end-of-line integration platform could not only facilitate the integration of PCMs for integrated reconfigurable photonics but also open up the possibilities for integrating other excellent optoelectronic materials in the future silicon photonic process design kits.