To increase the light extraction efficiency of an infrared light-emitting element.SOLUTION: An infrared light-emitting element 1 comprises: a GaAs substrate 2; and a semiconductor laminated part 3 formed on one face 21 of the GaAs substrate. A first conductivity type semiconductor layer 31 of the semiconductor laminated part is formed from a material including In and Sb. The semiconductor laminated part has a first mesa part 301 and a second mesa part 302. A boundary of the first mesa part and the second mesa part is located on a GaAs substrate side with respect to a luminescent layer. In a cross section perpendicular to the one face 21, an angle α formed by a reference line segment S1 and a one-face line L21 satisfies 32.2°α≤90°, and an angle β formed by a reference side-face line L1 and the one-face line L21 satisfies 32.2°β≤90°. The reference line segment S1 is a line segment that connects between a center point A of the luminescent layer and a common point B of the one-face line L21 in the one face 21, and it does not cross a second side-face line L302 forming a side face of the second mesa part. The reference side-face line L1 is a straight line including the second side-face line L302, and it does not cross a first side-face line L301. A rear face 22 of the GaAs substrate 2 is a light-extraction face.SELECTED DRAWING: Figure 7
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