Germanium-tin laser for silicon photonics is CMOS compatible

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

Germanium-tin laser for silicon photonics is CMOS compatible
Germanium-tin laser for silicon photonics is CMOS compatible
A scanning-electron-microscope (SEM) photograph shows the GeSn microdisk laser perched on a Ge pedestal. (Image: 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 occuring towards the disk edge is said to lead to better performance.

Source: IEDM 2015


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.

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