DEFECT STRUCTURE AT A CDTE(111) GAAS(001) INTERFACE/

This paper addresses the defect structure, as observed by transmission electron microscopy, at a CdTe(111)/GaAs(001) interface. When viewed along the [1(1) over bar0$]CdTe direction, the overlayer exhibits a hi gh density of microtwins parallel to the CdTe(111) growth direction. M eanwhile, when viewed along [11(2) over bar]CdTe, an array of misfit d islocations, exhibiting edge component of Burgers vector equal to a/4[ <(1)over bar 10>], a = 6.48 Angstrom, are observed at the interface be tween the CdTe and GaAs lattices. These misfit dislocations are of suc h a spacing as to be consistent with only partial relief of the misfit strain. The residual misfit strain is found to relax in a region exte nding about 200 Angstrom from the interface, with the source of the st rain relief being layer dislocations in the CdTe overlayer. The distan ce over which the misfit relaxes is consistent with the results of X-r ay measurements of the misfit relaxation in thin overlayers. Furthermo re, the distance over which the misfit relaxes is the same as that whi ch the high density of microtwins are observed, suggesting that the mi crotwins act as nucleation sites for the observed layer dislocations.