Experimental and theoretical investigations on the defect and optical properties of S- and Al-doped GaSe crystals

Abstract

A combination of experimental and computational methods was performed to investigate the defect and optical properties of S-doped and Al-doped GaSe crystals. Our experimental and calculated results indicate that the doped S and Al atoms can form S_Se and Al_Ga⁺ substitutional defects in the layered GaSe structure. The non-isovalent Al_Ga⁺ defect can strengthen the chemical bonding within the intralayer and induce complex defects within the interlayer in the layered GaSe structure. Al-doping maximally improves the hardness of GaSe, which makes it a promising nonlinear frequency conversion material in the infrared and THz ranges. The isovalent S_Se defect determines the GaSe_1−xS_x mixed structure. Calculated results indicate that the refractive index of GaSe_1−xS_x decreases with the x value, while the band gap increases. The unique properties of GaSe_1−xS_x may make it a potential candidate for double heterojunction photoelectric materials.