Index-guided laser array with select current paths defined by migration-enhanced dopant incorporation and dopant diffusion

An index guided semiconductor laser comprising:

• a semiconductor substrate with at least one ridge etched on a first surface thereof;
• a first cladding layer of a first select conductivity type, said cladding layer having a dopant species therein and disposed in overlying contiguous relation with respect to the first surface of said semiconductor substrate;
• said first cladding layer extending spatially above said ridge;
• an active layer disposed in overlying contiguous relation with respect to said first cladding layer;
• a second cladding layer disposed in overlying contiguous relation with respect to said active layer;
• at least one current blocking layer disposed in said first cladding layer spatially below the top of said ridge, said blocking layer having a conductivity type opposite to the conductivity type of said first cladding layer except in the region of said ridge where the dopant species of said first cladding layer is sufficiently migrated therein to change the effective conductivity type to that of said first cladding layer thereby defining a current path through the first cladding layer via the ridge;
• and
• electrodes disposed on the outside surfaces of said substrate and said second cladding layer.

An index guided semiconductor laser comprising:

• a semiconductor substrate with at least one ridge etched on a first surface thereof;
• a first cladding layer of a first select conductivity type disposed in overlying contiguous relation with respect to the first surface of said semiconductor substrate, said first cladding layer being grown to a sufficient thickness over said ridge so as to reach an apex;
• an active layer disposed in overlying contiguous relation with respect to said first cladding layer;
• a second cladding layer of a second select conductivity type disposed in overlying contiguous relation with respect to said active layer, said second cladding layer having a dopant species therein such that the conductivity type of said second cladding layer is opposite to the conductivity type of said first cladding layer;
• at least one current blocking layer disposed in said second cladding layer and generally coextensive therewith, said blocking layer having a conductivity type opposite to the conductivity type of said second cladding layer except in the region overlying said ridge where the dopant species of said second cladding layer is sufficiently migrated therein to change the effective conductivity type to that of said second cladding layer thereby defining a current path through the second cladding layer to said ridge;
• at least one other current blocking layer disposed in said first cladding layer spatially below the apex of said first cladding layer over said ridge, said other blocking layer having a conductivity type opposite to the conductivity type of said first cladding layer so as to define a current path through the first cladding layer apex via the ridge;
• and
• electrodes disposed on the outside surfaces of said substrate and said second cladding layer.

In a process for fabricating index-guided lasers by patterning a semiconductor substrate of a first select conductivity to have a plurality of substantially parallel spaced apart ridges with sidewalls disposed on a first flat surface thereof, whereby facing sidewalls together with the flat surface form a flat-bottom groove lying between adjacent ridges;

• growing a first cladding layer of the first conductivity type as the substrate over the first surface of the substrate;
• growing an active layer in overlying relation with respect to said first cladding layer;
• and
• growing a second cladding layer of opposite conductivity type to said first cladding layer in overlying relation with respect to said active layer, the improvement comprises:
• growing at least one current blocking layer in overlying relation to a portion of at least one of said cladding layers, in a region sufficiently close to the ridges so as to effect a dopant migration from the adjacent cladding layer portion into the current blocking layer, said current blocking layers being doped to have a conductivity type opposite to the conductivity type of its adjacent cladding layer portion, said dopant migration in the vicinity of said ridges being sufficient to effectively change the conductivity type of said current blocking layer to the conductivity type of the adjacent cladding layer.