The liquid-phase-epitaxial (LPE) process has proven to be a very effective technique for the formation of high-quality III-V semiconductor layers. It has found widespread use because devices made by this method produce high-efficiency LED's and low-threshold lasers. A limitation of this method has been the difficulty of making smooth high-quality surfaces. It will be shown that the use of a specially designed LPE growth apparatus makes possible the growth of reproducible uniform economical and, above all, smooth photolithographic processable layers. This process has made possible the formation of planar monolithic AlxGa1-xAs LED's with luminance characteristics as high as 104 ft L at a current density of ∼40 A/cm 2. © 1972 The American Institute of Physics.