Germanium-tin laser for silicon photonics is CMOS compatible

Nov. 17, 2015
The GeSn microdisk laser emits at 2.5 μm; paper to be presented at IEDM 2015.

At the IEEE International Electron Devices Meeting (IEDM) 2015 (7 to 9 December, 2015; Washington, DC) a team from several European research organizations and universities, led by the Forschungszentrum Jülich institute (Rostock, Germany), will report on a silicon-based direct-bandgap germanium-tin (GeSn) microdisk laser that emits at a lasing wavelength of 2.5 μm at a power output of 221 kW/cm2.1

The device was built using standard CMOS-compatible processing and was monolithically integrated on a silicon platform. Its 560-nm-thick GeSn epitaxial layers were grown on Ge buffers/Si substrates. Its lasing performance arises from 1) straining the epitaxial layers so they become direct bandgap materials; and 2) its microdisk cavity architecture. The work is an important step toward integrated silicon photonics, as creating CMOS-compatible light sources has proven to be difficult for integrated photonics.

In the fabrication process, after epitaxy, the microdisk mesa is defined using a dry-etch process, then is undercut using a tetrafluoromethane (CF4) plasma. The disks are then passivated with an aluminum oxide (Al2O3) layer. Strain relaxation occurring towards the disk edge is said to lead to better performance.

Source: IEDM 2015

REFERENCE:

1. Stephan Wirths et al., Paper 2.6, "Direct Bandgap GeSn Microdisk Lasers at 2.5 µm for Monolithic Integration on Si-Platform," Forschungszentrum Jülich/ Paul Scherrer Institute/ETH/University of Leeds/University of Grenoble/CEA LETI Minatec.

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!