SEMICONDUCTOR LASER

PURPOSE:To make a threshold current low, to realize a high-efficiency oscillation and to enhance reproducibility and reliability by forming a double heterojunction structure in which an active layer has been sandwiched between clad layers composed of a material whose band gap is wider than that of the active layer. CONSTITUTION:A double heterojunction structure in which an active layer 12 has been sandwiched between a first n-type AlGaAs clad layer 11 and a second p-type AlGaAs clad layer 13 which are composed of a material whose band gap is wider than that of the layer 12 is formed. The layer 13 has a protrusion-shaped region 15; and the region 15 is composed of a protrusion-part region 16 whose shape is close to a rectangle and of a slope-shaped bottom region 17 succeeding to it. In the region 16, its width is narrower than a carrier diffusion length and the region 17 becomes slope-shaped at least over the width of the carrier diffusion length on both sides from the center of the region 16. A multilayer structure in which a light-absorbing layer 18 has been buried on both sides excluding the region 16 is formed. Thereby, a threshold current becomes low, an oscillation can be performed with high efficiency, a functional transverse-mode oscillation is maintained, a noise is low, and this laser can be manufactured with high reproducibility and at a high yield.