Analysis and optimization of InGaAsP electro-absorption modulators

A numerical model of bulk electro-absorption modulators has been developed based on a quasi-two-dimensional drift-diffusion approach which includes both the presence of heterostructures and the Fermi statistics for the carriers. We show that the nonlinear behavior of this type of devices is essentially related to hole pile-up and space-charge effects. The simulation results compare favourably with some laboratory measurements on a fabricated device with abrupt hetero-junctions. Two other types of structures have been simulated, one obtained with the inclusion of a thin quaternary layer and the other with a, graded hetero-junction, which eliminate the hole pile-up at the InGaAsP-InP hetero-interface. The paper demonstrates that it is possible to approach the optimum behavior using both the alternatives considered here. Finally, nonlinear effects in short modulators have been investigated