Bell Telephone Laboratories

William A Bonner

Legrand G Van Uitert

Single crystals are conveniently produced by directional solidification of a liquid body under a pressurized atmosphere and, preferably, under a liquid encapsulating layer to minimize loss due to volatilization. Such fabrication entails a concern with internal stress in a grown crystal in the interest, e.g., of minimization of breakage of wafers cut from a crystal. According to the invention, minimization of stress is accomplished by means of a post-growth annealing step during which pressure is reduced substantially and, in particular, preferably to a pressure which does not exceed 50 percent of a pressure at which a constituent of the liquid body volatilizes. The method may be applied for producing single crystals of semiconductor materials as may be used as device substrates. In particular, the method is beneficial, e.g., for producing high-quality doped or undoped InP, GaP, and GaAs single crystals.

Minimization of strain in single crystals

Fabrication of single crystals of III-V semiconductor materials such as, e.g., indium phosphide by pulling from a melt may be hampered by twin formation. It has been discovered that twin formation is prevented by adjusting processing parameters such as, e.g., melt temperature, rotation rate, thermal gradients, and pull rate so as to limit rate of diameter enlargement of a boule. Specifically, diameter enlargement preferably does not exceed 0.3577 times the increase in length of a boule being pulled.

Production of single crystal II-V material

Magnetic garnet compositions grown from a novel flux comprising a mixture of Li.sub.2 MoO.sub.4 and R.sub.2 (MoO.sub.4).sub.3 wherein R represents yttrium or a rare earth element having an atomic number from 62 to 71 have appropriate magnetic properties for use in bubble domain devices. Items produced are uniform in composition and may be of submicron thickness.

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Warren, NJ, United States of America

William A Bonner