Computer modeling of the electric field dependent absorption spectrum of multiple quantum well material

The authors present a simple computer model for the electric field dependence of the absorption of semiconductor multiple-quantum-well (MQW) structure that will be used to optimize the performance of MQW modulators. This model has been compared to absorption spectra derived from photocurrent measurements on a GaAs/(GaAl)As MQW p-i-n diode and it has been found that the well-established Stark shifts of the exciton and subband continua energies are significantly overestimated. This might be linked to uncertainty in knowing the electric fields over the wells; and if a drop of 1.4 V somewhere in the device is assumed, a much better match can be achieved between the theoretical and experimental shifts. Given this improved match in the shifts the reduction in the oscillator strengths and the broadening are modeled very well. It is concluded that the model is likely to prove a useful tool for optimizing electroabsorption modulator design