Alloy engineered germanium monochalcogenide with tunable bandgap for broadband optoelectrical applications

Germanium monochalcogenides (GeSe and GeS) are promising materials for various optoelectronic applications because of their solar range bandgaps, high carrier mobilities, high stabilities, earth abundance, and anisotropic optical properties. Precise control of germanium monochalcogenide bandgaps is critical to applications in continuously tunable optoelectronics. In this paper, we combine first-principles calculations and experiments to predict and confirm that alloy engineering is a significant strategy for tailoring germanium monochalcogenide (GeS1-xSex) optoelectronic properties. When the Se content x increases from 0.0 to 1.0, the bandgap decreases from 1.23 to 0.89 eV. In addition, there is a direct-indirect bandgap transition when x is approximately 0.3. Tunable GeS1-xSex bandgaps can open up exciting opportunities for the development of various electronic and optoelectronic devices.