Silicon photonics continues to progress tremendously, both in near-infrared datacom/telecoms and in mid-IR optical sensing, despite the fact a monolithically integrated group IV semiconductor laser is still missing. GeSn alloys are one of the most promising candidate materials to realize such devices, as robust lasing under optical pumping was demonstrated by several groups up to mild cryogenic temperatures. Ideally, the integrated lasers should be tunable by design over a wide spectral range, offering a versatility that is required for optical sensing devices. We present here an innovative approach, taking advantage of local strain management in the semiconductor laser’s active zone. Arrays of differently strained Fabry-Pérot GeSn microlasers were fabricated side-by-side on the very same chip after blanket epitaxy on a Ge-buffered silicon-on-insulator substrate. Thanks to the local strain design, laser emission over a very large wavelength range under optical pumping, with laser lines peaking from 3.1 up to 4.6 μm at 25 K and with thresholds lower than 10 kW·cm–2. Laser operation persists up to 273 K, that is, very close to room temperature. This strategy, implemented on group IV semiconductors, opens up a new route to control the emission properties of microlasers integrated on a chip over significant photon energy windows representing a significant step forward in the integration and miniaturization of light sources emitting at a process-defined wavelength.

We have quantified the impact of various process parameters on the growth of thin, pseudomorphic SiyGe1-x-ySnx layers on 2.5 µm Ge buffers (themselves on Si(001) substrates). For GeSn layers, we found that 100 Torr was appropriate for the growth of high crystalline quality layers. The impact of the HCl mass-flow on the growth kinetics of thin Ge1-xSnx layers was also evaluated. Adding HCl retained Ge in the gaseous phase, resulting at 325°C in a growth rate decrease and a Sn content increase. Moreover, the growth of Ge1-xSnx was shown to be selective against SiO2 and SiN-covered Si substrates, even without HCl. Finally, various Si2H6 flows were added to the gas mixture to grow pseudomorphic SiGeSn layers. The quality of these layers was assessed by X-ray diffraction (XRD), wavelength dispersive X-ray fluorescence (WDXRF) and atomic force microscopy (AFM).