High Thermal Stability of Tensile Strained Direct Gap GeSn Crystallized on Amorphous Layers

Abstract

In this paper, we systematically research the thermal evolution of substitutional Sn composition, tensile strain, and the direct band gap of highly (111) textured, direct gap Ge1-xSnx (0.075<x<0.085) thin films crystallized on amorphous SiO2 layers. We show highly effective strain induced band engineering in Ge1-xSnx(111) films towards enhanced direct-gap semiconductor properties, which can be used as high performance optoelectronic materials for monolithic 3D electronic-photonic integration. A dilatational deformation potential of a=-12.8±0.8 eV is derived. We also demonstrate that the tensile strained GeSn crystallized on amorphous layers offers high thermal stability and fabrication/operation robustness for integrated photonics. The effects of geometrically-confined growth on the thermal stability of Ge1-xSnx were also explored by using laser annealing to induce the nucleation of different GeSn patterns. With the suppression of grain boundaries in patterned GeSn, 10-13 at.% Sn is retained at 600 °C.