Exploring the Potential of Microwave Annealing for Enhancing Si‐based GeSn Lasers

ABSTRACT We present an investigation on the effect of low‐thermal‐budget microwave annealing (MWA) on the structural and light‐emitting properties of compressively strained GeSn films deposited on a Ge‐buffered (001) Si substrate. After post‐growth annealing at MWA powers below 1050 W, the Sn content and strain in the GeSn films remained nearly unchanged, whereas the material quality improved, thereby enhancing light‐emitting efficiency. Annealing GeSn films at an MWA power of 1650 W induced strain relaxation and then reduced light‐emitting efficiency caused by the generation of misfit dislocations. Annealing GeSn films at MWA powers above 2100 W resulted in significant bidirectional thermal diffusion of Sn atoms, leading to the formation of substantial Sn clusters within the GeSn film, the emergence of β‐Sn droplets on the film surface, and Sn diffusion into the Ge buffer layer; this resulted in reduced Sn content in the GeSn film and light‐emitting efficiency. Results obtained on optically pumped GeSn lasers, fabricated using the as‐grown and annealed GeSn samples, indicated the significantly improved lasing threshold and maximum lasing temperature via MWA of GeSn films. These results indicate that MWA is a promising low‐thermal‐budget approach for improving the material quality and light‐emitting efficiency, thereby enhancing the performance of GeSn‐based lasers intended for use in silicon photonics.