THE ENERGY OF AN ARRAY OF DISLOCATIONS .2. CONSIDERATION OF A CAPPED EPITAXIAL LAYER

An analysis is presented of the energy of a periodic array of pairs of dislocations in an infinite body. It is then applied to the assessment of the energy changes induced by the introduction of a dipole-like array, on the upper and lower surfaces of a capped epitaxial layer. The analysis is sufficiently simple that 'compound arrays' can also be assessed. General formulae are presented and it is shown, in a particular case, that arrays generated by symmetrical slip from nuclei on one interface relax the mismatch with a smaller energy penalty than a simple array. Other compound arrays will exist which display the same property. It is concluded that mechanisms other than the introduction of threading dislocations are likely to be of relevance to the degradation of some semiconductor heterostructures.