Abstract: A method for manufacturing the semiconductor laser device comprising the steps of sequentially forming an active layer, a photo-waveguide layer, a cladding layer, and an ohmic contact layer on an upper surface of an InP substrate; forming a first patterned dielectric layer on the ohmic contact layer; depositing a patterned photoresist on the ohmic contact layer to define a p- electrode stripe layer; forming the p- electrode stripe layer only on a part of the ohmic contact layer; performing an annealing process; etching back the layers until the photo-waveguide layer is exposed, using the first patterned dielectric layer and the p- electrode stripe layer as an etching mask, to form a ridge; depositing a second dielectric layer on the substrate formed thus; selectively removing the second dielectric layer to form a contact hole on the p- electrode stripe layer; coating a bonding pad metal layer on the second dielectric layer and in the contact hole; and coating an n- electrode metal layer on bottom surface of t

Abstract: An avalanche photodiode in which a strained superlattice structure is used as a multiplication layer, comprising: an n.sup.+ type InP substrate; an n.sup.+ type InP epitaxial layer formed on a main surface of the substrate; an N type In.sub.1-x Al.sub.x As layer formed on the epitaxial layer; an n.sup.+ type In.sub.1-x Al.sub.x As layer formed on the N type In.sub.1-x Al.sub.x As layer, the n.sup.+ type In.sub.1-x Al.sub.x As layer having a relatively high impurity concentration more than the N type In.sub.1-x Al.sub.x As layer; the multiplication layer deposited on the n.sup.+ type In.sub.1-x Al.sub.x As layer, the multiplication layer having an In.sub.0.53 Ga.sub.0.47 As/In.sub.1-x Al.sub.x As superlattice structure; first and second p.sup.+ type In.sub.1-x Al.sub.x As layers laminated sequentially on the multiplication layer; an absorbing layer formed on the second p.sup.+ type In.sub.1-x Al.sub.x As layer, the absorbing layer being made of an In.sub.0.53 Ga.sub.0.