
Disclosed is a new type of transparent GaAs photo electric layer formed on an optical window made of a GaP single crystal substrate via an Al.sub.x Ga.sub.(1-x) As buffer layer, in which a gradual-lattice-constant layer of quadruple Al.sub.x Ga.sub.(1-x) PyAs.sub.(1-y) compound crystal is formed between the GaP single crystal substrate and the Al.sub.x Ga.sub.(1-x) As buffer layer. The y content in the gradual-lattice-constant layer of quadruple Al.sub.x Ga.sub.(1-x) PyAs.sub.(1-y) compound crys...










