Patent ID: 7859007

Claim:
An ultraviolet light-emitting device adapted to emit ultraviolet light in a wavelength range from 330 nm to less than 365 nm, said device comprising: a nitride semiconductor substrate having a dislocation density of at most 1E7 cm −2 ; an ultraviolet light-emitting layer that is adapted to emit the ultraviolet light in the wavelength range from 330 nm to less than 365 nm, and that is formed as a single layer comprising an InAlGaN quaternary alloy on a side of a first main surface of said nitride semiconductor substrate; 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 that of said Al x1 Ga 1-x1 N layer of the first conductivity type; and a first GaN layer of the first conductivity type and a second GaN layer of the second conductivity type arranged with 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 interposed between said first and second GaN layers; 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; wherein a composition ratio (x1, x2) of Al in said Al x1 Ga 1-x1 N layer of the first conductivity type and in said Al x2 Ga 1-x2 N layer of the second conductivity type is smaller than a composition ratio (1-x1, 1-x2) of Ga in said Al x1 Ga 1-x1 N layer of the first conductivity type and in said Al x2 Ga 1-x2 N layer of the second conductivity type; and wherein a total thickness of 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 is at most 0.4 μm.