Pseudo single crystal, direct-band-gap Ge0.89Sn0.11 on amorphous dielectric layers towards monolithic 3D photonic integration

Abstract

We demonstrate pseudo single crystal, direct-band-gap Ge0.89Sn0.11 crystallized on amorphous layers at <450 °C towards 3D Si photonic integration. We developed two approaches to seed the lateral single crystal growth: (1) utilize the Gibbs-Thomson eutectic temperature depression at the tip of an amorphous GeSn nanotaper for selective nucleation; (2) laser-induced nucleation at one end of a GeSn strip. Either way, the crystallized Ge0.89Sn0.11 is dominated by a single grain >18 μm long that forms optoelectronically benign twin boundaries with others grains. These pseudo single crystal, direct-band-gap Ge0.89Sn0.11 patterns are suitable for monolithic 3D integration of active photonic devices on Si.