Positron annihilation characteristics in GaxIn1-xAsySb1-y lattice matched to different substrates

Positron states in the quaternary cubic system GaxIn1-xAsySb1-y lattice matched to different substrates have been studied. The electron wavefunctions are calculated using the pseudopotential method within the virtual crystal approximation which includes the effects of compositional variations, whereas the positron wavefunction was solved with the ionic potential taken in the point-core approximation. Our calculations have shown that the effect of changing the substrate is generally significant as regards the positron states and related quantities. Moreover, it is found that the enhancement of the lattice mismatch leads to a decrease of the positron annihilation rate indicating the increase of the positron bulk lifetime which is confirmed by using the Siethoff relation (Phys. Stat. Sol. (b) 205 (1998) R3). (C) 2003 Elsevier B.V. All rights reserved.