Coherent light generators – Particular active media – Semiconductor
Reexamination Certificate
1998-06-12
2001-11-13
Leung, Quyen P. (Department: 2881)
Coherent light generators
Particular active media
Semiconductor
C372S050121
Reexamination Certificate
active
06317444
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to semiconductor optical devices, including lasers and electroabsorption modulators, and detectors.
Electroabsorption modulated laser (EML) devices have recently received a great deal of attention for use in high speed optical systems. Such devices typically include a semiconductor laser and modulator found in a single substrate. These devices usually include a semiconductor multi quantum well (MQW) active region, a contact layer formed thereover to facilitate electrical contact with the active layer, a current blocking layer for directing current to the active region, and a cladding layer to confine light to the active region. Zn is a commonly used p-type dopant for the blocking, contact and cladding layers, and the performance of the laser and modulator depends critically on the level of Zn in the various layers of the device.
It is desired to maintain a certain Zn dopant profile in the device structure for optimum performance. However, the Zn profile in the blocking and cladding layers may get modified during the growth of the contact layer due to the migration of the Zn dopant from the contact layer. One solution to the problem is to reduce the amount of Zn in the cladding, blocking, and contact layers. However, this approach also adversely affects other device properties, such as total device resistance.
It is desirable, therefore, to provide a process and resulting device which mitigate the problem of Zn migration in optical devices.
SUMMARY OF THE INVENTION
The invention in accordance with one aspect is an optical device comprising a semiconductor waveguide region (which may include an active region), a cladding region including a dopant comprising Zn, formed adjacent to the waveguide region, and a semiconductor contact region. The contact region is selected from the materials InGaAs and InGaAsP, and is formed over the waveguide region. The contact region includes a p-type dopant comprising carbon to provide sufficient conductivity to make low resistance contact to the waveguide region.
In accordance with another aspect, the invention is a method of fabricating an optical device including the steps of epitaxially forming a semiconductor waveguide region over the substrate, and forming a cladding region adjacent to the waveguide region, the cladding region including a dopant comprising Zn. A contact region selected from the materials InGaAs and InGaAsP is epitaxially formed over the waveguide region. The contact layer includes a p-type dopant comprising carbon to provide sufficient conductivity to make a low resistance contact to the waveguide region.
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Chakrabarti Utpal Kumar
Hamm Robert Alan
Seiler Joseph Brian
Shtengel Gleb E.
Smith Lawrence Edwin
Agere System Optoelectronics Guardian Corp.
Birnbaum Lester H.
Leung Quyen P.
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