Optically pumped germanium-tin micro-disks encapsulated by silicon nitride and transferred onto aluminum pillars generate a 2.5-micron laser beam with an ultra-low threshold. Laser beams with no III-V materials are no longer a dream… See results published in Nature Photonics.
- III-V materials, and especially gallium arsenide and indium phosphide, have been unchallenged in the world of laser emissions since the early 1960s. However, things shifted in 2015, when a laser effect was obtained from geranium-tin (GeSn). IV-IV semiconductors, which are more abundant and much cheaper than III-V semiconductors, may constitute an excellent alternative.
- This promising GeSn technology is being explored by CEA-Leti, together with French and German teams*. Their device, which was recently featured in Nature Photonics, confirms the 2015 demonstration. Through continuous or pulsed optical pumping, it emits a 2.5-micron laser beam with an ultra-low trigger threshold of 1.1 kW cm-2.
Our ultimate goal is to produce IV-IV lasers that operate in the mid-infrared range, explains Jean-Michel Hartman, CEA-Leti researcher.
Objective: Ambient Emission
- Producing the device starts by depositing germanium (Ge), and then GeSn, on a silicon substrate. The latter is an indirect band gap semiconductor, unsuited for emitting light due to its relatively low tin concentration (5%). But its encapsulation in live silicon drastically changes its band gap structure. Laser emission becomes a possibility. To dissipate heat locally, encapsulated GeSn is transferred onto aluminum pillars. The complete device resembles an oval table with support feet.
- It currently emits continuously pumped 70 K temperatures, rising to 100 K with pulsed pumping. Scientists would like it to function at room temperature (300 K). They are continuing their research as part of the ANR Elegante project, which will come to an end late 2021.
* STMicroelectronics, C2N-CNRS, Forschungs Zentrum Juelich