ON THE GENERATION OF A CROSS GRID OF EXTENDED SCREW-TYPE MISFIT DISLOCATIONS ON THE ZNSXSE1-X GAAS INTERFACE/

New sources for heterogeneous nucleation of both [110] and [1 ($) over bar 10] extended screw-type misfit dislocations to relax the lattice shear stress on the ZnSxSe1-x/GaAs interface have been observed for th e first time. These are identified as Shockley partial dislocations or iginating at the area close to the ZnSxSe1-x/GaAs interface. The Shock ley partials are formed for the accommodation of the stacking errors p roduced upon island coalescence. In-situ electron beam-induced heating studies were carried out to observe the dislocation generation mechan ism in the films. Our results show that the stress existing in the ZnS xSe1-x films gives rise to bowing of the threading segments of the Sho ckley partials. The bowing results from the fact that the dislocations are pinned at the film/substrate interface and at the film surface. T his process involves an increase in the length of the threading segmen ts under the stress sigma similar to 1 x 10(9) dyne cm(-2). With furth er accommodation of the lattice strain, the line tension of the bowing threading segments is relived by the movement of the pinning points a t the film surface with gliding of the threading segments toward the f ilm/substrate interface. This process is accompanied by the movement o f one or both of the pinned points at the film surface. Finally, a seg ment of extended screw-type dislocation is generated when the segments of the Shockley partials reach the ZnSxSe1-x/GaAs interface. A [110] extended screw-type interfacial dislocation is generated by gliding of the threading segments of the Shockley partials on [1 ($) over bar 11 ]-type planes with Burgers vectors b = a/6[1 ($) over bar 21]-type and a/6[2 ($) over bar 1 ($) over bar 1]-type toward the interface. On th e other hand, a [1 ($) over bar 10] extended screw-type interfacial di slocation is generated by gliding of the threading segments of the Sho ckley partials on (111)-type planes with Burgers vectors b = a/6[1 ($) over bar 21]-type and a/6[2 ($) over bar 1 ($) over bar 1]-type towar d the interface. Finally, the shear stress between the film and substr ate is relaxed by the generation of a grid of extended interfacial dis locations with screw components along the [110] and [1 ($) over bar 10 ] directions.