Abstract: The specification describes a liquid phase epitaxial (LPE) crystal growth process wherein semi-insulating epitaxial layers of gallium arsenide (GaAs) are formed on selected substrates by dipping the substrates into a saturated solution of GaAs in gallium. Prior to exposing the substrates to the above solution, the substrates are shielded by a nonreactive container of a material possessing a high thermal conductivity which, when immersed in the solution, serves to establish a thermal equilibrium between the substrate and the solution. This insures good nucleation in and crystal growth of the high quality semiconductor layers grown, and these layers may be grown to minimum thicknesses on the order of 0.2 micrometers or less with excellent control.