PATTERNED SUBSTRATE EPITAXY SURFACE SHAPES

This article describes a comprehensive technique to determine the shapes of GaAs epitaxial layers grown by organometallic chemical vapor deposition (OMCVD) on patterned substrates. A simple technique called the Borgstrom construction, which can predict epitaxial shapes, is reviewed. However, the assumptions in this model limit its applications and the Wulff construction is needed. The Wulff construction can predict edge shapes for constrained and unconstrained (such as at the edge of a mask) epitaxial growth. This technique is valid for any geometric situation assuming the growth rate versus orientation (growth rate polar diagram) is known. A semi-empirical growth rate polar diagram is given for GaAs at 750-degrees-C and atmospheric pressure OMCVD. The predictions made by the Wulff construction compare favorably with experimental results.