Web Growth of Semiconductors

Abstract

A novel process for growth of diamond‐lattice semiconductors is described, and a model is proposed for the growth mechanism. For germanium the process yields extended thin flat sheets, typically 1 cm wide and 0.1 mm thick, of good crystalline quality and relatively flat {111} surfaces. The sheet, or web, freezes from a liquid film drawn up by surface tension between two coplanar dendrites which originate from a single seed and are grown from the melt simultaneously with the sheet. Resistivity throughout the sheet is quite uniform. Etching of germanium webs shows them to be essentially dislocation‐free and does not reveal any microsegregation of impurities. Silicon and indium antimonide have also been grown in this manner. The proposed model postulates that although the dendrites at either side of the web grow beneath the melt surface in usual dendritic fashion, the faces of the web itself normally have no extension below the melt surface. The exterior contact angle between the solid and liquid surfaces is less than 180° but greater than the equilibrium contact angle which would be observed if the flat faces extended beneath the melt surface. In spite of this the grown faces are plane and vertical, thickening of the web being restricted by difficulty of nucleation. In this respect the predictions of this model are significantly different than for Čzochralski or floating‐zone growth. Extensive experimental observations, including deliberately produced irregularities, verify the predictions of the model.