Capping Layer Effects on Sb2S3-based Reconfigurable Photonic Devices

Ting Yu Teo*, Nanxi Li*, Landobasa Y. M. Tobing, Amy S. K. Tong, Doris K. T. Ng, Zhihao Ren, Chengkuo Lee, Lennon Y. T. Lee, Robert Simpson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Capping layers are essential for protecting phase change materials (PCMs) used in non-volatile photonics technologies. This work demonstrates how (ZnS)0.8-(SiO2)0.2 caps radically influence the performance of Sb2S3 and Ag-doped Sb2S3 integrated photonic devices. We found that at least 30 nm of capping material is necessary to protect the material from Sulfur loss. However, adding this cap affects the crystallization temperatures of the two PCMs in different ways. The crystallization temperature of Sb2S3 and Ag-doped Sb2S3 increased and decreased respectively, which is attributed to interfacial energy differences. Capped and uncapped Ag-doped Sb2S microring resonator (MRR) devices were fabricated and measured to understand how the cap affects the device performance. Surprisingly, the resonant frequency of the MRR exhibited a larger red-shift upon crystallization for the capped PCMs. This effect was due to the cap increasing the modal overlap with the PCM layer. Caps can, therefore, be used to provide a greater optical phase shift per unit length, thus reducing the overall footprint of these programmable devices. Overall, we conclude that caps on PCMs are not just useful for stabilizing the PCM layer, but can also be used to tune the PCM crystallization temperature and reduce device footprint. Moreover, the capping layer can be exploited to enhance light-matter interactions with the PCM element.
Original languageEnglish
Pages (from-to)3203–3214
JournalACS Photonics
Volume10
Issue number9
Early online date1 Sept 2023
DOIs
Publication statusPublished - 20 Sept 2023

Keywords

  • dielectric capping materials
  • wide bandgap chalcogenide phase change materials
  • tunable
  • integrated photonics
  • optical switches
  • microring resonators

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