Univ. Grenoble Alpes, Grenoble, France, CEA, LETI, Minatec Campus, Grenoble, France, CEA-INAC, Univ. Grenoble Alpes, Grenoble, France

Two approaches have been compared for the low temperature epitaxy of thick, partially relaxed GeSn layers on top of Ge strain relaxed buffers. The benefit of using step-graded instead of constant composition layers when targeting really high Sn contents (16%, here) was conclusively demonstrated. Digermane (Ge2H6) and tin-tetrachloride (SnCl4) were used as Ge and Sn precursors, respectively. The growth pressure (100 Torr) and the F(Ge2H6)/F(SnCl4) mass-flow ratio being constant, it was through a temperature lowering that the Sn concentration in the graded structure was increased. X-ray diffraction, atomic force microscopy and transmission electron microscopy were used to gain access to the Sn concentration, the strain state, the surface morphology and thicknesses of the heterostructures. Using a step-graded approach allowed us to gradually relax the strain in the GeSn layers. It helped us obtain high crystalline quality and avoid Sn segregation/precipitation for high Sn contents. © 2017 IOP Publishing Ltd.

atomic force microscopy, chemical vapor deposition processes, GeSn alloys, high resolution x-ray diffraction, semiconducting Ge

Atomic force microscopy, Chemical vapor deposition, Germanium, High resolution transmission electron microscopy, Temperature, Transmission electron microscopy, Vapor deposition, X ray diffraction, Chemical vapor deposition process, Constant composition layers, GeSn alloys, Graded structure, High resolution X ray diffraction, High-crystalline quality, Low temperature epitaxies, Strain relaxed buffers, Tin