STRAIN DIAGNOSIS OF (001)INGAAS AND (111)INGAAS LAYERS BY OPTICAL TECHNIQUES

A quantitative assessment of the lattice-mismatch in (001) and (111)B InGaAs/GaAs layers, of several compositions and variable thicknesses, is performed by optical techniques, and compared with determinations o f residual strain obtained by double-crystal X-ray diffraction. Nomars ki microscopy, photoluminescence, and Raman spectroscopies are used to analyze the surface morphology, material quality, and strain relaxati on. The relaxation evolution is discussed for those orientations. The critical layer thickness is estimated, being larger for (111)B. A non- uniform lattice accomodation is revealed by the spatial resolution of microprobe optical studies, where regions of different strain degree a re observed in (111)layers. Together with the plastic deformation indu ced by misfit dislocations for both (001) and (111)B orientations, an elastic relaxation is also deduced from variations of the strain degre e with depth, which is related to surface roughness.