STRAIN EFFECTS ON THE ENERGY-BANDS OF ZNSE FILMS GROWN ON GAAS SUBSTRATES BY SPECTROSCOPIC ELLIPSOMETRY

Room-temperature spectroscopic ellipsometry measurements were carried out on ZnSe thin films grown on (001)GaAs substrates by molecular-beam epitaxy for the study of the lattice mismatch-induced strain at the i nterface. The magnitude of the absorption coefficient at the E0+DELTA0 critical point is very sensitive to the strain in the film. The varia tion in the magnitude of the absorption coefficient is used to estimat e the critical thickness for the onset of dislocation generation. Almo st complete relaxation of the films was obtained for thicknesses highe r than 500 nm. Also, the strain-induced coupling between the valence s ubbands was found to cause additional shifting of the light-hole subba nd.