Bell Telephone Laboratories

Daniel Leon Rode

Norman E Schumaker

A process for improving the smoothness of semiconductor layers grown by epitaxy is described. Smooth epitaxial layers, free of crystal terraces, are attained by misorienting the growth surface of the substrate from a major crystallographic plane by a small critical angle approximately equal to the tread-to-riser angle of terraces which would be formed if the epitaxial layer were deposited on a growth surface nominally parallel to the major plane. The critical angle is a function of both the growth temperature and the crystal composition. Specific examples for the growth of LPE Al.sub.x Ga.sub.1-x As at various growth temperatures and values of x on GaAs substrates misoriented from the (100) and (111)B major planes are given. Also described are examples of silicon layers grown by CVD on (111) substrates to measure the critical angle in the (112) direction.

Growing smooth epitaxial layers on misoriented substrates

Described is a liquid phase epitaxy technique using conventional slider apparatus in which, after heating the source solution to saturation, the solution temperature is rapidly reduced so that supersaturation takes place but heterogeneous nucleation does not. The solution is allowed to reach convective equilibrium and only then is brought into contact with the substrate. Once in contact, the temperature is maintained constant so that convection currents in the solution are substantially reduced. This technique has several advantages: reduced edge growth, increased usable wafer area, and reduced wipe-off problems.

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Murray Hill, NJ, United States of America

Daniel Leon Rode