Abstract: The present invention provides monolithic-structure type photodiodes in which the first photodiode is sensitive to an optical signal having one wavelength and the second photodiode is sensitive to another optical signal having a different wavelength, and in which the first and second photodiodes are superimposed together with an optical filter layer interposed between them which separates a multiplex optical signal into the first and second wavelength signals. Owing to their monolithic structure, the photodiodes of the present invention are extremely useful for receiving multiplex optical signals having a plurality of different wavelengths.

Abstract: A plurality of single-crystal epitaxial layers of semiconductors are simultaneously grown on a plurality of suitable substrates from the liquid phase by a method which includes the step of consecutively, and at times simultaneously, supplying small portions of liquid solution from a solution reservoir onto all the surfaces of the substrates in a plurality of wells which are provided on a surface of a rotatable circular lower plate so that epitaxial growth can be simultaneously carried out in all wells. The solution reservoir is positioned on a radius of the lower plate on which a circular upper plate is also provided in a non-rotatable state relative to the solution reservoir. Small portions of liquid solution are supplied by rotating the lower plate relative to the upper plate and the solution reservoir, and constrained in shape and volume which are adjusted by the upper plate and the wells. The composition and doping level of epitaxial layers are controlled through vapor-liquid communication.

Abstract: Single-crystal epitaxial layers of compound semiconductors or mixed semiconductors are grown on suitable substrates from the liquid phase, which consists of a molten metallic solvent dissolving a source material of the semiconductors, and within which the temperature gradient is produced so that in a high temperature region of the liquid solution a solid source material is dissolving into the liquid solution with at least a portion of the solid source material always at an undissolved state and in a low temperature region of the liquid solution an epitaxial layer is depositing onto the substrate, the temperatures in the liquid solution being kept constant during the epitaxial growth. Each substrate is positioned in one of a number of slots which are provided in the upper surface of a slider and it is successively transferred with the slider to contact with the liquid solution.