| 摘要 |
We have found a way to, e.g., substantially increase the number of layers in a pseudomorphic strained layer semiconductor mirror (e.g., 32) over the number obtainable in an analogous conventional mirror, making it possible to obtain pseudomorphic strained layer mirrors of increased reflectance. Such a pseudomorphic mirror consists of alternating layers of a first and a second semiconductor material (e.g., 321, 322) (e.g., Gex Si1-x/Si), of thickness t1 and t2, and refractive index n1 and n2, respectively, with the number of layer pairs chosen such that the mirror thickness is less than or equal to the "critical thickness" Lc. For thicknesses > Lc the mirror will contain dislocations. An article (30) according to the invention comprises a mirror (e.g., 32) whose layer thicknesses are chosen such that n1 t1 NOTEQUAL n2 t2, with n1 t1 + n2 t2 = p lambda /2, (p being an odd integer, typically 1). In other words, the optical thickness of the layers is not the conventional p lambda /4. The thicknesses are also chosen such that the average lattice mismatch between substrate and mirror is reduced, compared to the analogous conventional ( lambda /4) mirror. Mirrors according to the invention can be advantageously used in optoelectronic devices such as surface emitting lasers and p-i-n photodetectors. <IMAGE> |
