Structural features of Sigma=19, [110] GaAs tilt grain boundaries

Sigma = 19, [110] tilt grain boundaries have been observed to facet paralle l to particular planes; the facets lie along ((3) over bar3 (1) over bar)(A )/(3 (3) over bar3 (1) over bar)(B), ((5)over bar>58>)(A)/7 (7) over bar4>) (B) and ((2) over bar2 (7) over bar)(A)/(4<(4)over bar5>)(B). The structura l unit of the Sigma = 19 ((3) over bar3 (1) over bar>)(A)/(3 (3) over bar(1 ) over bar)(B) [110] boundaries consists of 5- and 7-member rings, which ar e similar to the core structure of a/2[110] edge dislocations. The polariti es in each grain on either side of the boundaries has been confirmed by CBE D methods; a lower number of anti-site type cross-boundary bonds occur alon g the boundaries compared to when the polarity of one grain is reversed. Th e presence of 7-member rings and anti-site cross-boundary bonds results in a more open atomic structure at the boundary, shortening the distance betwe en the first and the second {331} atomic planes from the boundary plane by 40%. (C) 2001 Kluwer Academic Publishers.