Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Development ohmic electrical contact for application in a waveguide optical isolator

In the isolator configuration studied and demonstrated within the ISOLASER project, the ferromagnetic metal film not only is the source of the non-reciprocal effect, but also serves as the electrical contact for the underlying semiconductor optical amplifier. Consequently, an ohmic electrical contact needs to be developed with this metal. Traditionally, the In0.53Ga0.47As compound is used for the highly doped semiconductor layer at the metal-semiconductor interface. For the isolator contact this material is not suitable as it is highly absorbing at the operation wavelength of 1300nm, hence the modal loss that needs to be compensated would enhance seriously.

The quality of four alternative contact structures have been experimentally extracted and compared with the standard In0.53Ga0.47As layer. These alternatives were both structures with a bulk In0.81Ga0.19As0.41P0.59 layer and hybrid structures with a 100nm In0.81Ga0.19As0.41P0.59 layer topped with a thin (15nm and 5nm) In0.53Ga0.47As layer. Contact test structures (Cross Bridge Kelvin Resistors) have been fabricated and characterized.

Furthermore, the influence of rapid thermal annealing on the contact quality has been studied. It could be concluded that the addition of a 15nm InGaAs layer on top of a 100nm InGaAsP layer results in a contact quality that is close to that of the standard InGaAs structure and this realizes an ohmic electrical contact without significantly enhancing the modal absorption. This contact scheme has been used in all isolator demonstrators realized within the project.

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