Development of GeSn epitaxial films with strong direct bandgap luminescence in the mid-wave infrared region using a commercial chemical vapor deposition reactor

Germanium tin (GeSn) is a material of interest for electronic and photonic device applications, but its development and commercialization have been limited by material quality issues and lack of availability from epitaxy suppliers. In this paper, we report initial studies in optimizing GeSn films deposited on a Ge buffer layer grown on 200-mm diameter silicon (Si) substrates with an ASM Epsilon 2000 chemical vapor deposition reactor designed for commercial production. Using a single-step growth process, a Sn content up to 22% near the surface of a GeSn film was achieved due to the increase in Sn incorporation via strain relaxation. A two-step growth process resulted in a bilayer structure with a nearly 100% relaxation on the first layer, followed by a higher quality GeSn layer with 18% Sn as evident by a high photoluminescence intensity emitting in the mid-wave infrared region at 3.2 μm at 20 K.