InGaP etch stop
OwnerOleg V. Smolski, Jeff A. Bullingtoninventors
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Abstract
Our wafer scale processing techniques produce chip-laser-diodes with a diffraction grating that redirects output light out the top and/or bottom surfaces. Noise reflections are carefully controlled, allowing significant reduction of the signal fed to the active region. In GaAs substrate embodiments, prior art gratings have generally been in AlGaAs. By using a InGaP layer epitaxially grown over (preferably directly on the top of) the core, our lasers can have an etch-stop-layer for accurate vertical location of the grating, and provides an aluminum-free grating (avoiding problems of aluminum oxidation), and also enables fabrication of saw-tooth gratings using anisotropic etching of InGaP.
Claims9
An improved method of generating light within a GaAs semiconductor structure having an upper metal contact over an active region and a lower metal contact on at least a portion of a substrate bottom, and transmitting a substantial portion of the generated light out a surface of the semiconductor structure, said method comprising:
- providing a GaAs semiconductor substrate;
- providing a core layer containing active region and passive region longitudinally-displaced from the active region over said substrate, and wherein said active region comprises at least one quantum well;
- providing an InGaP top cladding layer on said core layer, said InGaP layer having a top surface;
- providing a top electrode layer over said top cladding layer;
- providing the top metal contact on said top electrode layer over said active region;
- providing the bottom metal contact on least a portion of said substrate bottom;
- etching to expose at least a portion said top-cladding top-surface over said passive region and providing grating fingers extending down into said top cladding layer over at least a portion of said passive region, wherein using said InGaP provides an etch-stop for said etching;
- and
- applying a voltage between said top and bottom metal contacts, whereby light is generated in said active region and a substantial portion of the generated light is transferred out a top surface of the passive region.
An improved semiconductor laser diode, said laser diode comprising:
- a GaAs semiconductor substrate;
- a core layer comprising an active region and a passive region on said substrate, said passive region being longitudinally-displaced from the active region, and wherein said active region comprises at least one quantum well;
- an upper InGaP cladding layer on said core layer, having a top surface;
- and
- grating fingers extending down into said top cladding layer over at least a portion of said passive region, wherein using said InGaP provides an etch-stop for locating said top surface.
An improved method of fabricating a GaAs semiconductor structure, said method comprising:
- providing a GaAs semiconductor substrate;
- providing a core layer containing active region and a waveguide region longitudinally-displaced from the active region over said substrate;
- providing an InGaP top cladding layer on said core layer;
- providing a top electrode layer over said top cladding layer;
- and
- etching to expose at least a portion said top-cladding top-surface over said waveguide region and providing grating fingers extending down into said top cladding layer over at least a portion of said passive region, wherein using said InGaP provides an etch-stop for said etching.
Dependencies are inferred from the claim text.