Solid phase epitaxy of GeSn alloys on silicon and integration in MOSFET devices

We investigate the crystallization of amorphous Ge alloy layers on silicon substrates for optical and electronic applications. Amorphous GeSn layers are obtained by limiting the adatom surface mobility during deposition. Subsequent annealing transforms the amorphous layer into single-crystalline GeSn by solid phase epitaxy. Structural investigation shows excellent structural quality for layers with up to 6.1 % Sn. The surface and interface are smooth thanks to the low thermal budget. The GeSn layers show a significant increase in optical absorption with respect to Ge. We demonstrate tensile-strained GeSn p-type pMOSFET devices on Si(111) substrates using solid phase epitaxy of amorphous GeSn layer, with 4.5 % Sn and +0.33 % tensile strain. Structural investigation showed the presence of twin defects in the GeSn layers after crystallization. In this work we present a method to effectively suppress the formation of twin defects. Furthermore we demonstrate the crystallization of multiple amorphous layers in a 1 step anneal