THE WEAK-BEAM CONTRAST OF OVERLAPPING STACKING-FAULTS

Thin (< 80 nm) layers of ZnSe grown on (001)-oriented GaAs contain a v ariety of both partially and fully pyramidal configurations of triangu lar {111} stacking faults whose apices are at, or close to, the interf ace. It was found that one format of these fault groupings exhibited e xtrinsic-type strong-beam characteristics but two distinct classes of contrast when examined under specific weak-beam conditions. The contra st behaviour is described and discussed in relation to the contrast ex pected for different model structures of the overlapping groupings sug gested by their high-resolution edge-on examination.