Strong extended SWIR cavity resonances in a single GeSn nanowire

Abstract

Nanowires are promising platforms for realizing ultra-compact light sources for photonic integrated circuits. In contrast to impressive progress on light confinement and stimulated emission in III-V and II-VI semiconductor nanowires, there has been no experimental demonstration showing the potential to achieve strong cavity effects in a bottom-up grown single group-IV nanowire, which is a prerequisite for realizing silicon-compatible infrared nanolasers. Herein, we address this limitation and present the first experimental observation of cavity-enhanced strong photoluminescence from a single Ge/GeSn core/shell nanowire. A sufficiently large Sn content (~ 10 at%) in the GeSn shell leads to a direct bandgap gain medium, allowing a strong reduction in a material loss upon optical pumping. Efficient optical confinement in a single nanowire enables many round trips of emitted photons between two facets of a nanowire, achieving a narrow width of 3.3 nm. Our demonstration opens new possibilities for ultrasmall on-chip light sources towards realizing photonic-integrated circuits in the underexplored range of extended SWIR.

Research progress of out-of-plane GeSn nanowires

“…For GeSn materials, the following methods have been reported to solve the problem of increased compressive stress by increasing Sn doping: (i) RTA process; (ii) Wrapping insulating stressor layer on the GeSn surface; (iii) Successive deposition of a tensile-stressed Ge buffer layer and a tensilestressed GeSn layer [150]. For out-of-plane GeSn NWs, core/ shell NW geometries were used to provide an additional degree of freedom in accommodating the effects of strain in the growth of lattice-mismatched heterostructures [56,145,151,152], where the strain relaxation of the shell increases with the increase in the thickness of the free surface of the sidewalls and the elastic compliance of the NW cores allows an increase in the strain relaxation of the shell to adapt to the lattice mismatch of the system and avoid buckling [131]. In addition, the bandgap is tuned by modulating the Sn content in the GeSn material, which in turn modulates the emission properties of the GeSn components [153].…”

“…Currently, the application of out-of-plane GeSn NWs is still in the phase of basic research and technology development. However, the literature indicates that out-of-plane GeSn NWs have many potential applications, especially as infrared photodetectors [55,62,91,159,162,[166][167][168], high-efficiency Li-ion battery anodes [122], nanowire SWIR lasers [152,169,170], nanowire transistors (figure 8) [55,60,61,[171][172][173][174][175].…”

“…In addition to potential applications in optical infrared detectors and lithium-ion batteries, Kim et al found that GeSn NWs also have potential applications in infrared lasers [152,170]. They performed the first experimental observation of a strong cavity resonance in a single Ge/GeSn core/shell NW fabricated by the bottom-up method.…”

Direct bandgap quantum wells in hexagonal Silicon Germanium

“…However, with their standard cubic-diamond crystal structure, silicon, germanium, and SiGe-alloys are all indirect band gap semiconductors, impeding the use of silicon-based materials for lasers and optical amplifiers for integrated photonics 1 . Several strategies have been investigated for integrating light emitting materials on silicon, including III-V 2,3 , GeSn [4][5][6][7][8][9] , strained Ge 7,10 , and SiGe quantum wells and dots [11][12][13][14][15][16][17] , but remain challenging due to various reasons. When transformed into the hexagonal crystal structure, the hex-Si 1−x Ge x alloys 18 are direct bandgap semiconductors with the fundamental bandgap at the Γ-point.…”