Patent ID: 7772586

Claim:
An optical semiconductor device, comprising an n-type cladding layer, an active layer and a p-type cladding layer on an InP substrate, wherein said p-type cladding layer has a superlattice structure comprising plural first layers and plural second layers alternately laminated; each of said first layers employs MgZnCdSe, each of said second layers employs ZnTe; a p-type carrier concentration of the p-type cladding layer having said first layers and said second layers is equal to or larger than 1×10 17 cm −3 , and is equal to or smaller than 1×10 22 cm −3 ; and a layer thickness of each of said first layers is larger than that of each of said second layers, and a band gap width of each of said first layers is larger than that of each of said second layers.