Effect of an applied electric field on intersubband transitions in strained In xGa 1− xAs/InP coupled double step quantum wells

Abstract

A new approach has been introduced for the fabrication of light-modulation and switching devices with the goal of producing the large Stark effect. A large tunability of the intersubband transition energy under an applied electric field is observed in the strained In x Ga 1− x As/InP coupled double step quantum well consisting of a shallow In 0.63Ga 0.37As quantum well and a deep In 0.75Ga 0.25As quantum well. The electronic subband energies and the corresponding wavefunctions in the In x Ga 1− x As/InP double step quantum wells without and with applied electric fields are calculated by a transfer matrix method taking into account strain effects. The transition energy and Stark shift of the In x Ga 1− x As/InP coupled double quantum well are much more sensitive to the applied electric field than those of the In x Ga 1− x As/InP single step quantum well and the behavior of the double step quantum well is followed by the physical properties of the coupled double quantum well rather than those of the single step quantum well. These results indicate that the large Stark shifts can be achieved for the strained In x Ga 1− x As/InP coupled double step quantum wells and that the double step quantum wells may hold promise for potential applications such as new types of modulators and two-color infrared photodetectors.