Effect of thermally induced charged-carrier transfer on near-infrared intersubband transitions inInxGa1−xAs/AlAs/AlyAs1−ySb/InPcoupled quantum-well structure

Abstract

We have investigated the near-infrared intersubband transition (ISBT) influenced by thermally induced charged-carrier transfer in strongly coupled ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_{y}{\mathrm{As}}_{1\ensuremath{-}y}\mathrm{Sb}$ quantum-well structures lattice matched to InP substrates. We have compared the ISBT's in symmetric and asymmetric coupled quantum-well structures by investigating the temperature-induced change in the carrier distribution in the subband states. Qualitatively different behavior is found in symmetric and asymmetric coupled quantum-well structures. In these structures, the change in the built-in dc space-charge electric field due to charged carrier transfer results in a blueshift of the ground to the first excited state ISBT with increasing temperature. This blueshift along with the associated redshift of the higher excited state ISBT on increasing the temperature is larger in near-symmetric structures indicating a stronger coupling between the adjacent wells compared to the asymmetric structures. The thermal stability of ISBT in coupled structures is more compared to that in single quantum wells. The interface quality significantly affects the ISBT energy in these structures.