Patent ID: 7436870

Claim:
A semiconductor laser device comprising: an n-type cladding layer, an active layer, and a p-type cladding layer, each of the active, n-type cladding, and p-type cladding layers being a III-V compound semiconductor, and supported by a substrate of n-type GaAs; a p-type band discontinuity reduction layer of a III-V compound semiconductor, on the p-type cladding layer; and a cap layer of p-type GaAs on the p-type band discontinuity reduction layer, wherein the p-type cladding layer, the p-type band discontinuity reduction layer, and the p-type cap layer are sequentially arranged in the order listed and are each doped with a p-type dopant which is lower in diffusivity than Zn, and the p-type band discontinuity reduction layer has a concentration of the p-type dopant lower in diffusivity than Zn of at least 2.5×10 18 cm −3 .