The Effect of Buffer Types on the In_0.82Ga_0.18As Epitaxial Layer Grown on an InP (100) Substrate

In_0.82Ga_0.18As epitaxial layers were grown on InP (100) substrates at 530 °C by a low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique. The effects of different buffer structures, such as a single buffer layer, compositionally graded buffer layers, and superlattice buffer layers, on the crystalline quality and property were investigated. Double-crystal X-ray diffraction (DC-XRD) measurement, Raman scattering spectrum, and Hall measurements were used to evaluate the crystalline quality and electrical property. Scanning electron microscope (SEM), atomic force microscope (AFM), and transmission electron microscope (TEM) were used to characterize the surface morphology and microstructure, respectively. Compared with the In_0.82Ga_0.18As epitaxial layer directly grown on an InP substrate, the quality of the sample is not obviously improved by using a single In_0.82Ga_0.18As buffer layer. By introducing the graded In_xGa_1−xAs buffer layers, it was found that the dislocation density in the epitaxial layer significantly decreased and the surface quality improved remarkably. In addition, the number of dislocations in the epitaxial layer greatly decreased under the combined action of multi-potential wells and potential barriers by the introduction of a In_0.82Ga_0.18As/In_0.82Al_0.18As superlattice buffer. However, the surface subsequently roughened, which may be explained by surface undulation.