Using high resolution photoluminescence(PL)-spectroscopy and cathodoluminescence(CL)-microscopy, the shift, splitting and polarization of the luminescence of free and dislocation bound excitons is studied, investigating the plastic relaxation of MBE grown II-VI Semiconductors ZnSe(001) and CdTe(001) on GaAs(001) and CdTe(111) on Si(111) substrate. A structural model was established, which describes the nucleation, independent spread and crystallographic alignment of α- und β-dislocations in (001) grown heterostructures, which is in accordance with all experimental observations. It has been shown, that the so called Y luminescence (2.61eV for ZnSe, 14.7eV for CdTe) has its origin in the recombination of excitons, which are bound on polar 60°-α-dislocations, in the investigated materials. In contrast to the latter, non-radiative carrier recombination has been detected on 60°-β-dislocations using plastic deformation by nanoindentation technique. For the luminescence of the dislocation bound exciton a remarkable high linear polarization parallel to the dislocation line direction has been observed. Both, the polarization and the binding energy of the exciton are in excellent agreement with the theoretical prediction of carriers bound in onedimensional electronic potentials. It has been reported for the first time that for ZnSe as well as CdTe a finestructure of the Y-luminescence can be used for displaying the spatial distribution of the width of the stacking-fault of dissociated 60°-α-dislocations. After all, the linear polarization of the Y-luminescence has been correlated with the orthogonal polarization of the luminescence arising from recombination of impurity bound and free excitons. Through this, an anisotropic relaxation of the residual layer strain has been revealed down to a scale of few hundred nanometers. This has been explained by an strong asymmetric distribution of α- and β-dislocations with orthogonal line directions. In contrast to the (001) grown layers, the (111) growth surface of CdTe on Si(111) substrate preferentially relaxes through the formation of extensive domains of microtwins. The genesis of the domains is located at steps of the surface of the substrate. A control of this mechanism through a slight miscut of the substrate material is discussed on experimental results of transmissionelectron-microscopy (TEM).