Patent ID: 6977952

Claim:
A semiconductor device having a semiconductor multi-layer structure which includes at least one active layer including at least one luminescent layer of In x Al y Ga 1−x−y N (0<x<1, 0≦y≦0.2), and at least a part of said at least one luminescent layer acting as a quantum well, wherein said semiconductor device satisfies at least one of: a first condition that a threshold mode gain of said quantum well is more than 12 cm −1, and a second condition that said semiconductor device has an internal loss “α i ” (cm −1 ) which satisfies α i >12xn −α m (cm −1 ), where “α m ” is a mirror loss, and “n” is a number of said quantum well; and a third condition that said semiconductor device has a slope efficiency “S” (W/A) which satisfies: S<3×{α m /(12×n)}×[{(1−R 1 )√(R 2 )}/{(1−√(R 1 R 2 ))×(√(R 1 )+√(R 2 ))}], where “R 1 ” is a first reflectance of a first cavity facet, from which a light is emitted, “R 2 ” is a second reflectance of a second cavity facet opposite to said first cavity facet, “α m ” is a mirror loss, and “n” is a number of said quantum well, and wherein a differential gain “dg/dn” of said at least one active layer satisfies dg/dn≧1.0×10 −20 (m 2 )1 and standard deviations of microscopic and macroscopic fluctuations in a band gap energy of said at least luminescent layer are not more than 40 meV; and wherein said microscopic fluctuation is measured based on temperature dependence of a photoluminescence lifetime and wherein said microscopic fluctuation is controlled by heat treatment of said semiconductor device at a temperature between 850° C. and 1200° C.