Etching silicon nanopillars to emit telecom photons

Single photons in the optical telecommunication wavelength will be important for quantum networks that could improve communication and computing security. Silicon can host sources of single telecom photons, but they must be integrated into state-of-the-art photonic circuits.

While dry-etching techniques, such as the commonly used reactive ion etching, are more standard to fabricate photonic structures, radiation damage during etching can result in unwanted fabrication-related luminescent defects. Hollenbach et al. employed a wet-etching technique called metal-assisted chemical etching (MACEtch), which allowed them to make nanopillars in silicon without introducing any optically active or luminescent defects.

The MACEtch technique also permits precise control of the size, spacing, and areal density of the nanopillars. The authors produced a vertically aligned nanopillar array with a 5 μm nanopillar pitch, compatible with state-of-the-art photonic circuits, and a density of thousands of silicon nanopillars per square millimeter. After MACEtch, the team used ion implantation to create telecom photon emitters in each nanopillar.

The researchers evaluated the optical properties of the telecom photon emitters with laser scanning confocal spectroscopy. This showed the pillars have enhanced photon brightness compared to bulk silicon because the emitted light is vertically guided through the individual nanopillars.

These results suggest the low-cost, top-down nanofabrication technique could scale up single-photon emitters in silicon nanopillars.

“This research can be extended to the fabrication of complicated photonic structures, such as Fresnel lenses and optical resonators, that can be used for applications in quantum photonics,” said author Yonder Berencén.

Next, the authors will attempt to create single-photon emitters at specific locations in individual nanopillars.

Source: “Metal-assisted chemically etched silicon nanopillars hosting telecom photon emitters,” by Michael Hollenbach, Nagesh S. Jagtap, Ciarán Fowley, Juan Baratech, Verónica Guardia-Arce, Ulrich Kentsch, Anna Eichler-Volf, Nikolay V. Abrosimov, Artur Erbe, ChaeHo Shin, Hakseong Kim, Manfred Helm, Woo Lee, Georgy V. Astakhov, and Yonder Berencén, Journal of Applied Physics (2022). The article can be accessed at https://doi.org/10.1063/5.0094715 .

This paper is part of the Radiation Effects in Materials Collection, learn more here .