THE INFLUENCE OF POLARITY ON TWINNING IN ZINCBLENDE STRUCTURE CRYSTALS - NEW INSIGHTS FROM A STUDY OF MAGNETIC LIQUID ENCAPSULATED, CZOCHRALSKI-GROWN INP SINGLE-CRYSTALS

The polarity of {1 1 1} edge facets, anchored to the three-phase bound ary (TPB), which give rise to growth-twin nucleation in the shoulder r egion of a [0 0 1], S-doped, magnetic liquid encapsulated Czochralski (MLEC) grown, InP boule, has been studied by chemical etching and sync hrotron X-ray anomalous scattering. Analysis of the results indicates that both the formation of edge facets and the nucleation of twins occ ur preferentially on {(1) over bar (1) over bar (1) over bar}(P) faces . Of the four possible sets of edge facets, belonging to the {(1) over bar (1) over bar (1) over bar}(P) form, which are oriented so as to b e thermodynamically favored to be anchored to the TPB, two of them can give rise to the conversion of a {1 1 5} external shoulder facet to a {(1) over bar (1) over bar (1) over bar}(P) one upon twinning, while the other two can give rise to the conversion of a {1 1 4} external sh oulder facet to a {1 1 0} one. In both cases, twinning is only observe d when the {(1) over bar (1) over bar (1) over bar}(P) edge facets are anchored to the TPB, in a region where the shoulder angle is close to 74.21 or 70.53 degrees, facilitating the production of the {1 1 5} an d {1 1 4} external shoulder facets, respectively, prior to twinning. T hese observations are discussed in light of calculated surface energie s of the various internal and external facets. (C) 1998 Elsevier Scien ce B.V. All rights reserved.