Patent ID: 7943943

Claim:
A light-emitting device adapted to emit light in a wavelength range from 330 nm to 365 nm, comprising: a nitride semiconductor substrate having a dislocation density of at most 1E7 cm −2 ; a light-emitting layer that includes an InAlGaN quaternary alloy disposed on a side of a first main surface of said nitride semiconductor substrate, and that is adapted to emit the light in the wavelength range from 330 nm to 365 nm, and that has a band gap corresponding to the wavelength range from 330 nm to 365 nm of the emitted light; an Al x1 Ga 1-x1 N layer (0<x1<1) of a first conductivity type on the side of the first main surface of said nitride semiconductor substrate; an Al x2 Ga 1-x2 N layer (0<x2<1) of a second conductivity type located in a more distant position from said nitride semiconductor substrate than a position of said Al x1 Ga 1-x1 N layer of the first conductivity type relative to said nitride semiconductor substrate; and an In x Al y Ga 1-x-y N (0<x<0.2, 0<y<0.5) buffer layer having a thickness of 50 nm to 200 nm disposed between said light-emitting layer and said Al x1 Ga 1-x1 N layer of the first conductivity type; wherein: said InAlGaN quaternary alloy of said light-emitting layer is located between said Al x1 Ga 1-x1 N layer of the first conductivity type and said Al x2 Ga 1-x2 N layer of the second conductivity type; said light-emitting layer has a multiple quantum well structure including plural well layers and plural barrier layers, wherein said well layers and said barrier layers are arranged alternating with one another on said buffer layer, and at least said well layers are formed of said InAlGaN quaternary alloy; and said well layers have a composition of In x4 Al y4 Ga 1-x4-y4 N (0<x4<0.2, 0<y4<0.5) and said barrier layers have a composition of In x5 Al y5 Ga 1-x5-y5 N (0≦x5<0.2, 0<y5<0.5).