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Home   /   Thesis   /   Selective area growth of GeSn for infrared photonic devices

Selective area growth of GeSn for infrared photonic devices

Condensed matter physics, chemistry & nanosciences Radiation-matter interactions Solid state physics, surfaces and interfaces


Context. The capability to integrate active and passive optoelectronic devices on a Si wafer is an essential paradigm in the quest for the development of low-cost and energy-efficient data communication, imaging, and quantum sensing technologies. To this end, a monolithic all-group IV semiconductor platform is at reach using direct band gap GeSn semiconductors. Over the last decade, tremendous progress was made in the epitaxial growth of GeSn, where a direct band gap material (i.e. high efficiency for the optical emission) is obtained at Sn contents of >9 at.%. Prototypes of GeSn photodetectors, lasers, and LEDs have been fabricated from the short-wave infrared (SWIR: 1.5-3 µm) to mid-wave infrared (MWIR: 3-8 µm) wavelengths. The main bottleneck with the GeSn technology is, however, the large number of structural defects that severely reduces the efficiency of the photonic devices made using GeSn. This prevents a wide scale adoption of GeSn photonics in favor of conventional, yet expensive III-V and II-VI semiconductor technologies.
Project. The growth of GeSn is commonly performed on Si using Ge as an interlayer in a chemical vapor deposition (CVD) reactor, hence with an industrial-compatible fabrication process. However, the lattice-mismatch between GeSn and the Ge/Si substrate leads to compressive strain in GeSn and plastic strain relaxation results in structural defects. Defects are a source of nonradiative recombination and largely contribute to the dark current of GeSn photonic devices, in turn strongly reducing efficiency. This thesis will overcome these challenges and develop the selective area growth (SAG) of defect-free GeSn p-i-n diodes from nanometer-size openings that are patterned into an oxide mask layer on Si. The SAG has proven to be a highly valuable approach for the integration of defect-free III-V semiconductors on Si, with similar results that are now being explored in Ge. The GeSn growth will be selectively confined in very small regions of the patterned oxide/Si wafer. In SAG reducing the lateral dimensions of the patterned oxide windows will strongly decrease the defect density in the epitaxially-grown GeSn layer through dislocation filtering. The unmatched crystalline quality of SAG GeSn will boost the efficiency of infrared optoelectronic devices and thus establish a robust, scalable monolithic infrared photonics platform using group IV semiconductor materials. Photodetector devices made of SAG GeSn p-i-n diodes will be fabricated as a template system to demonstrate the effectiveness of SAG compared to the existing GeSn technology based on unpatterned GeSn samples.


Institut de Recherche Interdisciplinaire de Grenoble
Université Grenoble Alpes
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