Phase transition and metallization of semiconductor GeSe at high pressure

Over the past few decades, semiconductor materials of the group IV-VI monochalcogenides have attracted considerable interest from researchers due to their rich structural characteristics and excellent physical properties. Among them, GeS, GeSe, SnS, and SnSe crystallize in an orthorhombic structure (Pbnm) at ambient conditions. It has been reported that GeS, SnS, and SnSe transform into a higher symmetry orthorhombic structure (Cmcm) at high pressure, while the phase transformation route of GeSe at high pressure remains controversial. As an IV-VI monochalcogenide, GeSe possesses excellent application prospects and has been extensively studied in the fields of optoelectronic and thermoelectric. Here we systematically investigate the structural behavior, optical and electrical properties of GeSe at high pressure. GeSe undergoes a phase transition from the Pbnm to Cmcm phase at 33.5 GPa, like isostructural GeS, SnS, and SnSe. The optical bandgap of GeSe decreases gradually as pressure increases and undergoes a semiconducting to metallic transition above 12 GPa. This study exhibits a high-pressure strategy for modulating structural behavior, optical and electrical properties of the group IV-VI monochalcogenides to expand its prospects in optoelectronic and thermoelectric properties.