Dynamics of above-barrier state excitons in multi-stacked quantum dots

Abstract

We report the relaxation dynamics from above-barrier exciton states to the lowest one in multi-stacked quantum dots (QDs). The photoluminescence decay time increases because of the excitation of higher exciton states, which is attributed to the wider miniband width of above-barrier excitons and the localization of the envelope functions in the barrier layers. The existence of the above barrier minibands makes carrier transport along the growth direction possible and eliminates a difficulty with close QD stacking. These results demonstrate an effective approach to achieve high efficiency QD devices. V

Enhancement of Optical Anisotropy by Interconnection Effect along Growth Direction in Multistacked Quantum Dots

“…[7][8][9][10] We have demonstrated the optical characteristics of the stacked InAs QDs grown on an InP (311)B substrate using a strain-compensation technique to fabricate high-density QD ensembles without dislocations [11][12][13] as the control method for the exciton characteristics. [14][15][16][17][18] As we have reported, a decrease in the growth-direction QD separation induces the change in the quantum confinement effects. While the HHs forming excitons are strongly localized in QDs, the electron envelope functions tunnel to the spacer layers (i.e., barrier layers) because of the difference in the less effective mass.…”

“…On the other hand, with decreasing d, P increases up to 41% in the d = 10 nm sample. Since the excitation energy of 1.38 eV is less than the band gap energy of the In 0.47 Ga 0.10 Al 0.43 As-spacer layer,18 the enhancement of the polarization is attributed to the changes in the optical characteristics of the QDs induced by the interconnection effect on the electron states. The polarization degree along the [011] direction is plotted as a function of the inverse of d in Fig.…”

Generation of nonlinear polarization to emit terahertz waves in above gap states in GaSb/AlGaSb multiple quantum wells

“…When a strain field is applied to semiconductor materials, stable energy states are created. 20,21) Previously, we suggested that the creation of stable nonlinear polarization is an essential factor for the THz wave emission. 22) Moreover, by showing the availability of these states as the source of the nonlinear polarization, the choice range of materials becomes wider.…”