Crystal wafer prodn. with large surface area - by liq. phase epitaxy using passivated substrate crystal with exposed nucleation centre

摘要

Prodn. of crystal wafers of large surface area by liq. phase epitaxy on a substrate crystal in which the growth rate is different in different crystal planes, involves providing a passivating layer preventing epitaxial deposition on the immersed surface of the crystal of orientation such that the lateral growth rate on this surface is greater than that in other directions, before immersion, except for a single area left open as nucleation centre. Pref. one tip of a machined and oriented seed crystal is used as nucleation centre and this is aligned with an inert carrier and a holder so that only the surface of the nucleation centreis exposed to the satd. liq. phase. The process is used in the prodn. of semiconductor wafers, e.g. for diodes, transistors and thyristors, of high crystal perfection, e.g. from Si, Ge or gp. III-V cpds., e.g. GaAs. Parting and machining operations and material losses are minimised.