Abstract

Group-IV GeSn alloys have been considered as a promising candidate for efficient light emitters on silicon for silicon photonics [1]. While conventional group-IV semiconductors including Si, Ge, and their alloys are the dominant materials for silcon electronics, they are not suitable for light sources because they are indirect-bandgap materials, Recently, a new group-IV GeSn alloys have emerged for efficient light sources because the bandgap can be turned into direct bandgap with a sufficient amount of Sn content. With the advances in low-temperature growth techniques to break the ~1% solid solubility of Sn in Ge, GeSn layers with Sn contents up to 36% have been demonstrated. Efficient GeSn lasers and LEDs have also been realized [1]. However, the low-temperature growth and the huge lattice mismatch between GeSn and Si or Ge (virtual) substrates usually results in significant defects that degrading the material quality [2]. Thermal annealing has been proposed to improve the material quality of GeSn. However, high-temperature annealing will lead to significant Sn segregation [3], thereby degrading the material quality of GeSn and hinder the device applications.

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