Semiconductor laser

Abstract

A semiconductor laser includes a semiconductor substrate of a first conductivity type; a double heterojunction structure comprising a lower cladding layer of the first conductivity type disposed on the semiconductor substrate and having a first energy band gap, a band gap discontinuity reduction layer of the first conductivity type having a thickness from five to forty nanometers disposed on the lower cladding layer and having a second energy band gap, an undoped active layer disposed on the band gap discontinuity reduction layer and having a third energy band gap smaller than the first energy band gap, the second energy band gap being intermediate the first and third energy band gaps, and an upper cladding layer of a second conductivity type, opposite the first conductivity type, disposed on the active layer and having a fourth energy band gap larger than the third energy band gap, the double heterojunction structure having a ridge shape; a current confinement structure disposed on opposite sides of the double heterojunction structure for confining current flow to the double heterojunction structure; and first and second electrodes electrically contacting the semiconductor substrate and the upper cladding layer, respectively.

Dependencies are inferred from the claim text.