Optical Gain Analysis of Graded InGaN/GaN Quantum-Well Lasers

Optical properties of graded InGaN/GaN quantum well (QW) lasers are analyzed as improved gain media for laser diodes emitting near 500 nm. These results are compared with those of conventional InGaN/GaN QW structures. The heavy-hole effective mass around the topmost valence band is found to nearly not be affected by the inclusion of the graded layer. The graded InGaN/GaN QW structure shows a much larger matrix element than the conventional InGaN/GaN QW structure. The radiative current density dependences of the optical gain are similar to each other. However, the graded QW structure is expected to have lower threshold current density than the conventional QW structure because the former has a lower threshold carrier density than the latter.