The present invention relates to a method for obtaining an n-type doped metal chalcogenide quantum dot solid-state element with optical gain for low-threshold, band-edge amplified spontaneous emission (ASE), comprising: —forming a metal chalcogenide quantum dot solid-state element, and —carrying out an n-doping process on its metal chalcogenide quantum dots to at least partially bleach its band-edge absorption, which comprises: —a partial substitution of chalcogen atoms by halogen atoms, in the metal chalcogenide quantum dots, and/or —a partial aliovalent-cation substitution of bivalent metal cations by trivalent cations, in the metal chalcogenide quantum dots; and —providing a substance on the metal chalcogenide quantum dots, to avoid oxygen p-doping. The present invention also relates to the obtained n-type doped metal chalcogenide quantum dot solid-state element, a method for obtaining a light emitter with that n-type doped metal chalcogenide quantum dot solid-state element, and the obtained light emitter.

A laser diode including a double heterostructure comprising a top layer, a buffer layer formed on a substrate, and an intrinsic active layer formed between the top layer and the buffer layer. The top layer and the buffer layer have opposite types of conductivity. The active layer has a bandgap smaller than that of the buffer layer or the top layer. The double heterostructure includes Ge, SiGe, GeSn, and/or SiGeSn materials.

A laser diode including a double heterostructure comprising a top layer, a buffer layer formed on a substrate, and an intrinsic active layer formed between the top layer and the buffer layer. The top layer and the buffer layer have opposite types of conductivity. The active layer has a bandgap smaller than that of the buffer layer or the top layer. The double heterostructure includes Ge, SiGe, GeSn, and/or SiGeSn materials.