Microheater hotspot engineering for repeatable multi-level switching in foundry-processed phase change silicon photonics

TL;DR

This paper presents a method to precisely control microheater hotspots in silicon photonics, enabling reliable multi-level phase change switching with high repeatability for advanced optical computing.

Contribution

It introduces re-engineered waveguide microheaters for deterministic multi-level switching of phase change materials, improving scalability and repeatability over prior stochastic approaches.

Findings

Achieved deterministic multi-level switching of Sb2Se3 and Ge2Sb2Se4Te alloys.

Demonstrated precise spatial control of temperature profiles in foundry-processed microheaters.

Validated the approach with transient thermoreflectance imaging.

Abstract

Nonvolatile photonic integrated circuits employing phase change materials have relied either on optical switching mechanisms with precise multi-level control but poor scalability or electrical switching with seamless integration and scalability but mostly limited to a binary response. Recent works have demonstrated electrical multi-level switching; however, they relied on the stochastic nucleation process to achieve partial crystallization with low demonstrated repeatability and cyclability. Here, we re-engineer waveguide-integrated microheaters to achieve precise spatial control of the temperature profile (i.e., hotspot) and, thus, switch deterministic areas of an embedded phase change material cell. We experimentally demonstrate this concept using a variety of foundry-processed doped-silicon microheaters on a silicon-on-insulator platform to trigger multi-step amorphization and reversible switching of Sb$_{2}$Se$_{3}$ and Ge$_{2}$Sb$_{2}$Se$_{4}$Te alloys. We further characterize the response of our microheaters using Transient Thermoreflectance Imaging. Our approach combines the deterministic control resulting from a spatially resolved glassy-crystalline distribution with the scalability of electro-thermal switching devices, thus paving the way to reliable multi-level switching towards robust reprogrammable phase-change photonic devices for analog processing and computing.