Infrared electroabsorption modulation at normal incidence in asymmetrically stepped AlSb/InAs/GaSb/AlSb quantum wells

A normal‐incidence modulation mechanism is proposed which uses the Stark effect to induce Γ‐L transitions in asymmetrically stepped AlSb/InAs/GaSb/AlSb quantum wells (QWs). A significant feature of this structure is the unusual band alignments which localize two deep wells for the Γ and L bands in adjacent layers, i.e., the Γ‐valley minimum is in the InAs while the L‐valley minimum is in the GaSb. In contrast to a square QW, where the Stark shifts for both Γ and L subbands are in the same direction, the two step wells for Γ and L valleys in the proposed structure are oppositely biased in the presence of an electric field. Therefore, the first Γ and L subbands move toward each other, making the Γ‐L crossover occur more efficiently. Near this point, most of the Γ electrons transfer to the L valleys, where they are allowed to make intersubband transitions under normally incident radiation. As a result, the device switches from being transparent to normal‐incidence light to strongly absorbing it. The calculat...

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