Large excitonic confinement in asymmetric quantum T wires

Abstract

An asymmetric quantum T wire (QTWR) may be formed whenever two quantum wells (QW) of differing widths intersect. We measured the photoluminescence and photoluminescence excitation from such QTWRs using microscope optics with high spatial resolution. The introduction of an asymmetry in the design of the QWs allows us to compensate for the different effective masses of the heavy holes in the (100) and (110) directions. We find that the confinement energy for excitons in the asymmetric QTWR is 40 meV, which is greater than previously published reports on symmetric QTWRs. Consequently, the confinement energy exceeds kT at room temperature, which appeals to device applications. Furthermore, the confinement energy is greater than the LO phonon energy, a feature which may improve the capture rate of the QTWR and decrease the escape rate at higher temperatures. Finally, using the results from calculations, we estimate the binding energy of the exciton to be about 20 meV, which is substantially larger than the binding energy in QWs. This result agrees with theoretical predictions of an increase in exciton binding energy in 1D confinement.