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We have investigated the epitaxial growth of Ge1-xSnx layers with a high Sn content over 10 % and their optical properties. We examined the growth of Ge1-xSnx epitaxial layers with Sn contents over 10 % on Ge and InP substrates. We have achieved the epitaxial growth of a Ge1-xSnx layer with a 27%-Sn content which is much higher than a thermoequilibrium solid solubility of Sn in Ge. We have also revealed the Sn content dependence of the direct energy bandgap for Ge1-xSnx layers with wide Sn contents ranging from 5 % to 27%