| 摘要 |
An active layer having a predetermined effective band gap, a predetermined effective refractive index, and a predetermined thickness is sandwiched between a first clad layer and a second clad layer. Each of the clad layers has an effective band gap wider than that of the active layer, an effective refractive index lower than that of the active layer, and a predetermined thickness. On the first clad layer, there is disposed a first stack structure doped to a first conductivity type, which alternately includes a layer of a high refractive index and a layer of a low refractive index, and has a discontinuity of a band of the first conductivity type made quite smaller than that of a band of a second conduction type. On the second clad layer, there is disposed a second stack structure doped to the second conductivity type, which alternately includes a layer of a high refractive index and a layer of a low refractive index, and has a discontinuity of a band of the second conductivity type made quite smaller than that of the band of the first conductivity type. Each of the first and second stack structures serves as an optical filter and also forms a low-resistance conduction path.
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