The liquid phase epitaxy of AlxGa1-xAs for monolithic planar structures

The most promising electroluminescent materials used for visible light emitting diodes (LEDs) are GaAsP, GaAlAs, GaP, and GaAs with phosphors. Presently, GaAsP, which is prepared by vapor phase epitaxy, is the only material which has found widespread commercial use. In this work an effort was made to explore the feasibility of fabricating planar monolithic GaAlAs LED arrays prepared by the liquid phase epitaxial (LPE) process. In order to accomplish this objective the LPE process was developed so that epitaxial layers of uniform thickness and essentially constant composition with smooth photoprocessable surfaces could be reproducibly grown at a reasonable cost. Through the use of special fixturing and proper adjustment of thermal gradients during the LPE growth, epitaxial layers of suitable quality were produced which were used to fabricate planar monolithic structures. A description will be given the preparation and processing of these structures. The electrical properties of the GaAlAs epitaxial layers and the electrical and optical characteristics of the planar monolithic structures fabricated will be discussed. The LPE process which has evolved in the growth of GaAlAs layers also has applicability for the LPE growth of GaP or amphoteric doped GaAs both of which have produced high efficiency LEDs so far by the LPE process only.