Speaker
Description
Ge1-xSnx alloys are promising CMOS-compatible materials for developing effective light absorbers and emitters integrated into Si opto- and nanoelectronics. Critical to this application is the transition from an indirect- to a direct-gap semiconductor, which is experimentally observed when the Sn content is in the 6–10 % range. The wide variation in Sn values is due to the sensitivity of the material to internal deformations and the doping level. We propose two approaches to mitigate local strain: 1) incorporating carbon © atoms, which have a significantly smaller covalent radius than Sn; 2) crystallizing amorphous GeSn films using rapid thermal processing to prevent Sn segregation. To implement these ideas, GeSn films formed by thermal or magnetron deposition were co-doped with carbon. Annealing was conducted using femtosecond (fs) or scanning continuous-wave (cw) lasers. The films were characterized using Raman spectroscopy, XRD, mass spectrometry, AFM. Mass spectrometry revealed a strong correlation between the distribution of Sn and C atoms in both unannealed and annealed films. Raman analysis of the annealed GeSn films demonstrated that fs laser annealing was the most effective method, achieving a high substitutional Sn content. Importantly, the properties of films annealed using a scanning cw laser approached those of the fs laser-annealed films. Given that scanning cw laser annealing is significantly more cost-effective and simpler than fs laser processing, and more efficient than traditional thermal annealing, its application presents a highly promising and scalable path for the fabrication of high-quality, direct-gap GeSn and GeSn:C films.
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