| 摘要 |
PURPOSE:To protect the title element from the lowering of its quantum efficiency which depends upon the crystal quality of a substrate and from the deterioration of its lifetime, which also depends upon the crystal quality as well, by a method wherein a multiplex hetero junction layer having a crystal lattice mismatching inductive strain is inserted in between the compound semiconductor substrate and an active layer. CONSTITUTION:A multiplex hetero junction layer 2a, which is used as a buffer and has a crystal lattice mismatching inductive strain, is provided between a compound semiconductor crystal substrate 1 and a buffer lower contact layer 2, which is a component of an active layer 8. The thickness (h) of the lattice mismatching layer of the layer 2a must be made smaller than the critical value, at which the generation of a crystal lattice mismatching inductive transition is caused. By contriving to satisfy this condition to the thickness (h), the dislocation existing in the crystal of the substrate 1 can be shielded from propagating to the epitaxial film grown thereon. Accordingly, in case the layer 8 consisting of the layer 2, a lower clad layer 3, an upper clad layer 5 and an active layer 4 is formed on the layer 2a with such a constitution, the crystal quality in the layer 8 can be rapidly improved. |
