All‐Around HfO₂ Stressor for Tensile Strain in GeSn‐on‐Insulator Nanobeam Lasers

Abstract Tensile strained GeSn alloys are considered a key enabler for the realization of complementary metal‐oxide‐semiconductor laser sources. However, the tensile strained GeSn lasers reported to date require complex fabrication processes for applying tensile strain in GeSn, preventing tensile GeSn lasers from becoming the mainstream technology for integrated photonics. Here, a unique strain engineering method is presented that can introduce a uniform tensile strain in GeSn lasers by harnessing a widely developed atomic layer deposition (ALD) process. 1D photonic crystal nanobeam lasers under homogenous tensile strain induced by an ALD HfO₂ all‐around stressor layer show a single‐mode lasing peak with a ≈31 nm redshift and ≈2 times intensity increase. The lasing threshold of tensile strained GeSn lasers is ≈12% improved compared to the unstrained GeSn lasers. It is believed that the approach offers a new path toward the realization of practical group‐IV laser sources for photonic‐integrated circuits.