Structural and optical measurements of residual strain and relaxation of lattice mismatched InGaAs/GaAs heterostructures

In this paper the effect of strain relaxation on the structural and optical properties of lattice mismatched InGaAs/GaAs heterostructures has been studied by means of X-ray diffractometry and photoreflectance spectroscopy. X-ray diffractometry reveals anisotropic strain relaxation, related to asymmetry in the formation of misfit dislocations, causing distortion of the epilayer unit cell and lowering its symmetry to orthorhombic. By using room temperature photoreflectance spectroscopy, we observed residual strain induced a splitting of valence band energies. The results were analyzed by means of deformation potential theory that enables us to estimate the extent of strain relaxation and the values of residual strain in the layers.