Microheater hotspot engineering for spatially resolved and repeatable multi-level switching in foundry-processed phase change silicon photonics
Hongyi Sun, Chuanyu Lian, Francis Vásquez, S. Kari, Yi‐Siou Huang, Alessandro Restelli, Steven A. Vitale, Ichiro Takeuchi, Juejun Hu, Nathan Youngblood, Georges Pavlidis, Carlos Rı́os
Abstract
Nonvolatile photonic integrated circuits employing phase change materials have relied either on optical switching with precise multi-level control but poor scalability or electrical switching with seamless integration and scalability but mostly limited to a binary response. The main limitation of the latter is relying on stochastic nucleation, since its random nature hinders the repeatability of multi-level states. Here, we show engineered 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. We experimentally demonstrate this concept using a variety of foundry-processed doped-silicon microheaters on a silicon-on-insulator platform featuring Sb2Se3 or Ge2Sb2Se4Te and achieve 27 cycles with 7 repeatable levels each. We further characterize the microheaters’ response using Transient Thermoreflectance Imaging. Our microstructure engineering concept demonstrates the evasive repeatable multi-levels employing a single microheater device, which is necessary for robust and energy-efficient reprogrammable phase change photonics in analog processing and computing. Stochastic nucleation prevents the repeatable multi-level response of phase change materials in integrated photonics. Here the authors circumvent this issue with a method using deterministic amorphization via spatially controlled microheater hotspots.