Single Crystalline GeSn on Silicon by Solid Phase Crystallization

Abstract

We investigate the crystallization of amorphous GeSn layers on silicon substrates. Amorphous GeSn layers are deposited on silicon substrates kept at approximately room temperature by molecular beam epitaxy. Thermal annealing transforms these layers into single crystalline GeSn. Structural investigation shows excellent structural quality for layers with 4.5% Sn. Furthermore the surface and interface are smooth, especially when considering the relaxation of the layers. The surface root mean square roughness is smaller than 1 nm. Finally, we show an increased optical absorption for the GeSn layers with respect to Ge, which is promising for integration of optical devices on silicon substrates.