A method for producing a light source comprising a first contact area, a second contact area and an active area juxtaposed parallel to a first direction (x) of a basal plan, said active area being located between the first and second contact areas (1, 2) in a second direction (y) of the basal plan, said method comprising the following steps: - Providing a first substrate comprising a stack in the third direction (z) normal to the basal plane of a first layer based on a first silicon or silicon-germanium material on a second layer based on a second material different from the first material, the second material being a dielectric material, said first layer being in contact with the second layer, - Forming, at the first layer, the first contact area, - Forming, at the first layer, the second contact area, - Forming, at the first layer, the active area, said method being characterised in that the active area comprises a base layer, said base layer being formed with the following successive steps: - Removing the first material in the active area over the entire thickness of the first layer so as to expose, on the one hand, a portion of a lower face based on the second material, and on the other hand, at least one face based on the first material normal to the basal plane, called the lateral face of germination (421, 422), having an edge in contact with said lower exposed face, - Forming a germination layer (71, 72) from a third material, the third material being germanium, with first epitaxial growth, called first lateral growth, of said third material from the at least one lateral face of germination (421, 422), said first growth being mainly directed in the second direction (y) and at least partially guided by the exposed portion of the lower face, the germination layer covering only partially the exposed portion of the lower face so that the germination layer (71, 72) has at least one face based on the third material normal to the basal plane, called the base lateral face, - Forming the base layer from a fourth material of a germanium-tin or indium phosphide InP alloy, differing from the third material, with a second epitaxial growth, called the second lateral growth, of the fourth material from the at least one base lateral face, said growth being mainly directed in the second direction (y) and at least partially guided by the exposed portion of the lower face, so that the exposed portion of the lower face is fully covered. - Providing a first substrate comprising a stack in the third direction (z) normal to the basal plane of a first layer based on a first silicon or silicon-germanium material on a second layer based on a second material different from the first material, the second material being a dielectric material, said first layer being in contact with the second layer, - Forming, at the first layer, the first contact area, - Forming, at the first layer, the second contact area, - Forming, at the first layer, the active area, said method being characterised in that the active area comprises a base layer, said base layer being formed with the following successive steps: - Removing the first material in the active area over the entire thickness of the first layer so as to expose, on the one hand, a portion of a lower face based on the second material, and on the other hand, at least one face based on the first material normal to the basal plane, called the lateral face of germination (421, 422), having an edge in contact with said lower exposed face, - Forming a germination layer (71, 72) from a third material, the third material being germanium, with first epitaxial growth, called first lateral growth, of said third material from the at least one lateral face of germination (421, 422), said first growth being mainly directed in the second direction (y) and at least partially guided by the exposed portion of the lower face, the germination layer covering only partially the exposed portion of the lower face so that the germination layer (71, 72) has at least one face based on the third material normal to the basal plane, called the base lateral face, - Forming the base layer from a fourth material of a germanium-tin or indium phosphide InP alloy, differing from the third material, with a second epitaxial growth, called the second lateral growth, of the fourth material from the at least one base lateral face, said growth being mainly directed in the second direction (y) and at least partially guided by the exposed portion of the lower face, so that the exposed portion of the lower face is fully covered.