Optical waveguide type photodiode and a process of producing the same

Abstract

An optical waveguide type photodiode has a plurality of semiconductor layers formed one upon another on a semiconductor substrate and including an optical absorption layer sandwiched between a pair of optical confinement layers for guiding incident light in parallel with the semiconductor layers, wherein a light absorption quantity per unit length of an optical waveguide area constituted by the optical absorption layer is substantially constant throughout the entire area thereof. Specifically, the optical confinement factor .GAMMA.(x) of the optical waveguide area is set so as to increase with guided distance x of light. Preferably, a device structure is employed in which the thickness d(x) of the optical absorption layer increases with the guided distance x of light. Also, the optical absorption layer is formed by selective area growth with the use of a pair of selective area growth masks, and these masks have a mask pattern such that the mask width thereof gradually decreases/increases in the light guiding direction, whereby a photodiode with the above device structure can be fabricated with ease.