Abstract
GeSn alloys are promising materials for CMOS-compatible mid-infrared lasers manufacturing. Indeed, Sn alloying and tensile strain can transform them into direct bandgap semiconductors. This growing laser technology however suffers from a number of limitations, such as poor optical confinement, lack of strain, thermal, and defects management, all of which are poorly discussed in the literature. Herein, a specific GeSn-on-insulator (GeSnOI) stack using stressor layers as dielectric optical claddings is demonstrated to be suitable for a monolithically integration of planar Group-IV semiconductor lasers on a versatile photonic platform for the near- and mid-infrared spectral range. Microdisk-shape resonators on mesa structures were fabricated from GeSnOI, after bonding a Ge0.9Sn0.1 alloy layer grown on a Ge strain-relaxed-buffer, itself on a Si(001) substrate. The GeSnOI microdisk mesas exhibited significantly improved optical gain as compared to that of conventional suspended microdisk resonators formed from the as-grown layer. We further show enhanced vertical out-coupling of the disk whispering gallery mode in-plane radiation, with up to 30% vertical out-coupling efficiency. As a result, the GeSnOI approach can be a valuable asset in the development of silicon-based mid-infrared photonics that combine integrated sources in a photonic platform with complex lightwave engineering.
Highlights
Low-cost and CMOS-compatible Si-based photonic technologies, like Silicon-On-Insulator (SOI), has enabled significant advances for on-chip optical processing in the near-infrared (IR) wavelength range, especially for highspeed detection and modulation of optical signals[1]
We show that GeSnOI stacks obtained through the bonding of GeSn active layers tackle all the above-mentioned issues: lattice mismatch interface defects management, compressive/tensile strain management, and optical confinement
We start with a presentation of the two kinds of structures. Both were based on a 500-nm-thick GeSn layer with 10.5% of Sn grown on a 2.5-μm-thick Ge strain-relaxed buffer (Ge SRB), itself on a 200 mm Si (001) wafer (Fig. 1a)
Summary
Low-cost and CMOS-compatible Si-based photonic technologies, like Silicon-On-Insulator (SOI), has enabled significant advances for on-chip optical processing in the near-infrared (IR) wavelength range, especially for highspeed detection and modulation of optical signals[1]. One of its major drawbacks, though, is the lack of monolithically integrated group-IV lasers. To compensate for the lack of such laser sources, strong efforts were devoted these past few years to the integration of III–V compounds with high lasing performances to boost silicon photonic technologies[2]. It was true for telecom applications in the near-infrared wavelength range. III–V lasers are the most standard and reliable light
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