| 摘要 |
PURPOSE:To diminish the development of strain, defects at the junction in a system having unmatched lattice by a method wherein the changing gradient in composition in an overshoot structure (corresponding to the changing gradient of lattice constant) is made more gentle. CONSTITUTION:After the epitaxial formation of lattice constant transition layers C, D (2) on the surface (a) of a substrate A (1) in lattice constant alpha, an epitaxial layer B (3) in a specific lattice constant beta is mounted on the surface (a). The lattice constant is gradually changed from the surface (a) to (c) so that the lattice constant(r) at the point (c) may exceed beta in the layer C. The excess level shall be 1/5-1/10 of the unmatched level of the lattice constant. After passing the point (c), the transition layer D (2) is provided to make the lattice constant approach to the lattice constant beta of the target layer B. The changing gradient shall be more gentle than that of the layer C so as to ease the strain. That is, about 1/3 of the gradient in the layer C will suffice for the changing gradient. In such a constitution, the changing rate of the lattice constant can be optimized, especially after exhibiting the overshoot structure, to be gradually changed thereby enabling a once imposed strain to be substantial ly eased. |
