It was proposed here that the dislocations which formed upon attaining a critical thickness in lattice-mismatched wide-gap II-VI/GaAs heterostructures could act as laser-light scatterers. An almost normally incident HeNe laser probe was used, during epitaxial growth, to generate both a specularly reflected laser-light signal and a non-specularly reflected or scattered light signal at epilayer thicknesses that were above the critical value. It was found that the scattered light originated within the bulk of the II-VI epilayer, rather than at the free surface; as deduced from observations of a -phase shift between simultaneous specular and non-specular reflections. A strong correlation was also observed between the dislocation density (as determined by post-growth transmission electron microscopy of ZnSe/GaAs heterostructures) and the scattered light intensity that was recorded  in situ  during the growth of such heterostructures. The refractive index perturbations which were necessary for such scattering had been considered theoretically to be the result of strong micro-electric fields which surrounded the dislocations during plastic deformation. The field distribution around a dislocation was considered with specific regard to 3 different potentials. These were the deformation potential, the charged dislocation potential and the piezoelectric potential. The magnitudes of these fields were considered with regard to ZnSe, and the electro-optical effect was used to explain how a refractive index perturbation (10-5 to 10-4) that was sufficiently large to scatter light could result from such fields.

C.M.Rouleau, C.J.Santana, K.S.Jones, R.M.Park: Journal of Applied Physics, 1995, 78[2], 1203-9