Epitaxial wafer and device

摘要

An epitaxial wafer and a device having improved characteristics are obtained. The epitaxial wafer includes a substrate (3), a buffer layer (9) formed on the substrate (3), a light-receiving layer (11) formed on the buffer layer (9), and a window layer (13) The light-receiving layer (11) is constituted of an epitaxial film having its lattice constant larger than that of a material of which the substrate (3) is made. The window layer (13) is formed on the light-receiving layer (11) and constituted of one or a plurality of layers arranged to contact the light-receiving layer (11). A constituent layer of the window layer (13) that is in contact with the light-receiving layer (11) has its lattice constant smaller than the larger one of respective lattice constants of the light-receiving layer (11) and the buffer layer (9). The window layer (13) has a thickness of at least 0.2 µm and at most 2.0 µm.