Structural and Electronic Response of Multigap N-Doped InSe: A Prototypical Material for Broad Spectral Optical Devices.

The production of controlled doping in two-dimensional semiconductor materials is a challenging issue when introducing these systems into current and future technology. In some compounds, the coexistence of distinct crystallographic phases for a fixed composition introduces an additional degree of complexity for synthesis, chemical stability, and potential applications. In this work, we demonstrate that a multiphase InSe layered semiconductor system, synthesized with three distinct structures─rhombohedral α and β-InSe and trigonal δ-InSe─exhibits chemical stability and well-behaved n-type doping. Scanning tunneling spectroscopy measurements reveal variations in the local electronic density of states among the InSe structures, resulting in a compound system with electronic bandgaps that range from infrared to visible light. These characteristics make the layered InSe system a promising candidate for multigap or broad spectral optical devices, such as detectors and solar cells. The ability to tune the electronic properties of InSe through structural phase manipulation makes it ideal for integration into flexible electronics and the development of heterostructures with other materials.