| 摘要 |
A first buffer layer (GaAs), a second buffer layer (AlGaAs), and a diffusion suppressing layer consisting of GaAs or AlGaAs are stacked on a GaAs substrate. The structure has a first cladding layer thereon. When AlGaAs is used for the diffusion suppressing layer, the Al ratio of AlGaAs is made smaller than in the second buffer layer. In such a structure, when a window region is formed, the diffusion rate of the impurity (Zn) can be lowered in the diffusion suppressing layer, and the diffusion of the impurity can be stopped at the second buffer layer.
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