Suppression of Zn diffusion into absorption layers in electroabsorption (EA) modulators due to the use of Ru-doped semi-insulating InP buried heterostructures

Zn diffusion into the multi quantum well (MQW) absorption layer of semi-insulating InP-buried electroabsorption (EA) modulators is investigated by two methods: One is a novel experimental method in which a planer-structured test sample is used to evaluate the diffusion. The other is a simulation of the extinction characteristics of Zn-diffused MQW absorption layers at various the Zn concentrations. The Zn diffusion experiment shows that Zn diffusion is suppressed by the use of Ru-InP burying layers. Comparing device characteristics to the simulation results shows that Zn diffusion into the absorption layer is effectively suppressed in a Ru-doped InP-buried EA modulator so excellent extinction characteristics can be achieved. These results indicate that Ru-doped InP-buried EA modulators are superior to Fe-doped InP-buried ones.