Si-based Germanium-Tin (GeSn) Emitters for Short-Wave Infrared Optoelectronics

Conventional integrated electronics have reached a physical limit, and their efficiency has been influenced by the generated heat in the high-density electronic packages. Integrated photonic circuits based on the highly developed Si complementary-metal-oxide-semiconductor (CMOS) infrastructure was proposed as a viable solution; however, Si-based emitters are the most challenging component for the monolithic integrated photonic circuits. The indirect bandgap of silicon and germanium is a bottleneck for the further development of photonic and optoelectronic integrated circuits. The Ge1-xSnx alloy, a group IV material system compatible with Si CMOS technology, was suggested as a desirable material that theoretically exhibits a direct bandgap when Sn composition increases. Last decade, efforts were made to develop high quality Ge1-xSnx films on Si substrate using commercial reactors. Moreover, the effect of Sn composition on the bandgap energy of Ge1-xSnx alloys was theoretically investigated. In this work, the development of Si-based Ge1-xSnx emitters was pursued with study the temperature-dependent bandgap emission of Ge1-xSnx structures for the short-wave infrared (SWIR) wavelength range (between 1.5 to 3 µm). The photoluminescence (PL) emissions from the bandgap of Ge1-xSnx films were investigated and a direct bandgap Ge1-xSnx was demonstrated for the first time based on the careful analysis of the PL spectra line-width and also the strain-dependent bandgap concept. In addition, the Ge1-xSnx advanced structure including SiGeSn/GeSn/SiGeSn single quantum well (QW) and Ge/Ge0.92Sn0.08/Ge double heterostructures (DHS) were studied. The GeSn QW PL emission was scrutinized from 10 to 300 K and the carrier confinement was analyzed through band offset calculations in the QW structure. Moreover, the electrical and optical characteristics of n-i-p Ge/Ge0.92Sn0.08/Ge light emitting diodes (LEDs) with surface emitting and edge emitting configurations were examined at different temperatures. Additionally, the lasing performance from the DHS Ge/Ge0.89Sn0.11/Ge waveguide was experimentally investigated based on the concept of direct bandgap Ge1-xSnx films and the confinement of carriers and optical field within the Ge/Ge0.89Sn0.11/Ge structure. Finally, an optimized QW design has been proposed that features a direct bandgap Ge0.9Sn0.1 QW with Type-I band alignment favorable for the high carrier confinement and low threshold Ge1-xSnx QW devices