| 摘要 |
PURPOSE:To obtain the titled device of high performance operating at low threshold value by making the construction in such a manner that the refractive index or the thickness of a plurality of isolation layers isolating a plurality of active layers from one another is successively increased from that of the center isolation layer toward that of the outside. CONSTITUTION:The active region is composed of a multilayer quantum well, and Al concentration (x) of a Ga1-xAlxAs region correcsponding to the top of the well is minimum at the center; as it goes to the periphery, the concentration increases stepwise. In such a manner, carries are confined in each well; since layer beam has a longer wavelength than the carrier, it is confined according to the distribution of refractive index as viewed on an average without being cntrolled by the distribution of the fine refractive index. The depth of each well is the same, however, the top of the well is lower toward the center, and higher toward the periphery. Therefore, the average refractive index is highest at the center, and presents the continuous changes lower toward the periphery. Thereby, the effect of confinement of carriers and laser beams can be exhibited to the maximum without haivng regions of large Al concentrations. |
