Compositional Dependence of the Quantum Confined Stark Effect in Quaternary Quantum Wells

Abstract

Quantum well modulators require strict control over the wavelength of the exciton transition in order to minimize insertion loss and maximize voltage sensitivity at the desired wavelength of operation. Within the quaternary material system In x Ga1− x As y P1− y , there are two parameters which can be varied in order to tune the bandgap: the thickness of the quantum well layer and its composition. Tuning the bandgap by means of well size alone is of limited usefulness since the rate at which the exciton energy shifts with field drastically decreases as well width decreases 1. In this paper, we demonstrate for the first time that the compositional flexibility of quaternary quantum wells can be used to obtain field-induced shifts larger than those obtainable in InGaAs quantum wells, yielding enhanced electroabsorption and electrorefraction. We show that quaternary devices can fill a serious need for quantum well optical modulators in the wavelength range 1.3 µm to 1.55 µm for optical communications.