GeSn lasers for monolithic integration on Si



Abstract:

Lasing under optical pumping is shown in suspended GeSn microdisks fabricated on a Ge virtual substrate with a lasing threshold below 1 mW at 20K.

Intensive research has been carried out in the last years on novel materials for the integration of advanced optoelectronic and photonic systems on silicon motivated by the prospect of cost-effectiveness resulting from compatibility with complementary metal-oxide-semiconductor (CMOS) circuits. To allow compatibility with silicon IC manufacturing facilities, group IV elements and their alloys have attracted special attention as active materials. GeSn is one of the most promising group IV alloys for laser applications due to the transition to a direct bandgap under tensile strain and/or sufficiently high Sn alloy content. Moreover, the smaller bandgap energy of GeSn alloys enables laser operation at the higher end of the near-IR range / lower end of the mid-IR wavelength range, enabling new sensing and bio-photonics applications.

Two types or resonators are mainly considered for monolithic integration on a Si platform: waveguide structures and microdisk resonators (MDRs). Lasing was recently demonstrated using waveguide structures. These may also serve as waveguide photodetectors in which the long cavity (absorption length) allows the efficient collection of photons. Laser cavities based on whispering gallery mode (WGM), such as MDRs, have been intensely investigated because of their simple device structure, high quality factor and relative ease of integration.

Here we present the fabrication on MDRs based on GeSn/Ge/Si heterostructures grown by chemical vapor deposition (CVD) and investigate their suitability as lasers cavities. Optically pumped lasing is demonstrated.