LARGE EXCITONIC CONFINEMENT IN ASYMMETRIC QUANTUM T-WIRE

An asymmetric quantum T wire (QTWR) may be formed whenever two quantum wells (QW) of differing widths intersect. We measured the photolumine scence and photoluminescence excitation from such QTWRs using microsco pe optics with high spatial resolution. The introduction of an asymmet ry 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 QT WR is 40 meV, which is greater than previously published reports on sy mmetric QTWRs. Consequently, the confinement energy exceeds kT at room temperature, which appeals to device applications. Furthermore, the c onfinement energy is greater than the LO phonon energy, a feature whic h may improve the capture rate of the QTWR and decrease the escape rat e at higher temperatures. Finally, using the results from calculations , we estimate the binding energy of the exciton to be about 20 meV, wh ich is substantially larger than the binding energy in QWs. This resul t agrees with theoretical predictions of an increase in exciton bindin g energy in 1D confinement. (C) 1997 Academic Press Limited.