Spinodal decomposition in InGaAsP epitaxial layers

In GaAsP epitaxial layers emitting in the 1.25-1.37 μm wavelength region have been evaluated using transmission electron microscopy, X-ray diffraction and photoluminescence. Electron diffraction patterns show elongation of the 400 spots in the <> direction and diffuse intensity on the low angle as well as on the high angle side. This observation is consistent with the extra scattering observed close to the 400 Bragg peaks by X-ray diffraction. Furthermore, microstructures exhibit quasi periodic fine scale structure having a wavelength of ≈ 150 Å, rectilinear boundaries and a weakly developed basket-weave pattern. These observations are compatible with the occurrence of spinodal decomposition in the layers. In addition, photoluminescence studies indicate that the presence of the fine scale composition modulations does not adversely affect the luminescence properties of these materials.