Abstract

Controlled dendritic growth of germanium from the melt yields long thin strips whose principal surfaces are optically flat {111} crystallographic planes except for the occasional presence of small steps. The crystals grow rapidly in the $〈211〉$ direction, have twin planes parallel to the flat surfaces, and can withstand an elastic strain exceeding ${10}^{\ensuremath{-}3}$. The distribution coefficients of impurities are close to unity compared to quasi-equilibrium values.A mechanism for dendritic growth is proposed, in which the presence of at least one properly oriented twin plane is fundamental and necessary. This mechanism explains most of the observed growth features in germanium dendrites, and is expected to apply generally to materials with the zincblende structure.The presence of the twin plane makes growth in opposite directions in the twin plane dissimilar, not only in the zincblende lattice but generally. The effect of this asymmetrization on the growth of $\ensuremath{\alpha}$-SiC is considered. A crystal growth mechanism based on this asymmetrization is proposed, which should be of general validity.