First and second order twin boundaries in edge defined film growth silicon ribbon

Abstract

The equilibrium defect structure of edge defined film-fed growth ribbons consists of linear twins and twin bundles lying parallel to the growth direction. These twins show similar etching behavior in spite of the fact that their electrical activity i.e. efficiency as recombination centers, can vary greatly. Correlated electron beam induced current microscopy and high voltage transmission electron microscopy show (i) that some of the linear boundaries consist of alternating sections of coherent first order twins and incoherent second order twins of the {111}/{115} type and (ii) that the first order twins are not electrically active, whereas the second order twins act as strong recombination centers. Structural models of the {111}/{115} interface indicate a large fraction of dangling bonds. Macroscopically, the alternating sections of these twin boundaries form single straight boundaries running parallel to the growth direction of the ribbon. In etching experiments the alternating sections of boundaries described above are therefore difficult to differentiate from coherent first order twins.