Room Temperature Lasing in GeSn Microdisks Enabled by Strain Engineering

Abstract

The success of GeSn alloys as active material for infrared lasers could pave the way toward a monolithic technology that can be manufactured within mainstream silicon photonics. Nonetheless, for operation on chip, lasing should occur at room temperature or beyond. Unfortunately, despite the intense research in recent years, many hurdles have yet to be overcome. An approach exploiting strain engineering to induce large tensile strain in micro‐disk made of GeSn alloy with Sn content of 14 at% is presented here. This method enables robust multimode laser emission at room temperature. Furthermore, tensile strain enables proper valence band engineering; as a result, over a large range of operating temperatures, lower lasing thresholds are observed compared to high Sn content GeSn lasers operating at similar wavelength.

Strain Engineered Electrically Pumped SiGeSn Microring Lasers on Si

“…As discussed, currently, the maximum lasing temperature is limited by the highest current that can be injected without damage. This maximum laser temperature is much below the 270 K lasing obtained by optical pumping of a 9 μm Ge 0.86 Sn 0.14 microdisk laser grown using the same epitaxial procedure and RPCVD reactor . Consequently, future work should focus on improving metal contacting, as well as the doping profiles to reduce unnecessary joule heating resulting from carrier transport.…”

“…This maximum laser temperature is much below the 270 K lasing obtained by optical pumping of a 9 μm Ge 0.86 Sn 0.14 microdisk laser grown using the same epitaxial procedure and RPCVD reactor. 15 Consequently, future work should focus on improving metal contacting, as well as the doping profiles to reduce unnecessary joule heating resulting from carrier transport. The current−voltage characteristics of the lasers with 5.5 μm outer radius reveal a ∼120 Ω series resistance that can be significantly improved via in situ doping.…”

“…From the design point of view, larger outer radii should allow reduction of the optical losses, but to fully leverage this the inner radius should also be increased accordingly. Furthermore, strain engineering 33 by silicon nitride stressors to induce tensile strain in the active GeSn region, that already enabled room temperature lasing under optical pumping, 15 provides a further path toward progress in the electrically pumped lasing temperature.…”

“…Here too, much progress has been made since the first demonstration of an optically pumped GeSn-on-Si laser . The (optically pumped) lasing temperature has been increased to room temperature (305 K). − Quantum-well lasers as well as continuous-wave operation have been demonstrated. Recently, electrical pumping has been reported, but restricted to very long Fabry–Perot cavities and thick epitaxial stacks in which light is vertically confined. , …”

Radiative Carrier Lifetime in Ge$_{1-x}$Sn$_x$ Mid-Infrared Emitters

“…Ge 1−x Sn x alloys constitute an emerging class of group IV semiconductors providing a tunable narrow bandgap, which has been highly attractive to implement scalable, silicon-compatible mid-infrared photonic and optoelectronic devices [1]. This potential becomes increasingly significant with the recent progress in nonequilibrium growth processes enabling high Sn content Ge 1−x Sn x layers and heterostructures leading to the demonstration of a variety of monolithic mid-infrared emitters and detectors [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Notwithstanding the recent developments in device engineering, the impact of structural characteristics on the basic behavior of charge carriers is yet to be fully understood.…”