Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.

accepted as the underlying mechanism for blinking, there is still uncertaintyabout how the electrons leave the QD and where they go and reside beforereturning. The results of Ref. 64 and the power law of Eq. (1) support a modelwherein the electrons leave by quantum mechanical tunneling (possibly Augerassisted) through the potential barrier at the surface, that the potential barrierfluctuates in height or width to affect the tunneling rate by five orders ofmagnitude, and that the external trap states to which the electrons transferhave an energy distribution and are relatively far from the surface of the QDcore. A critical feature of this model that is generally accepted is that the localenvironment around the QD fluctuates and is itself affected by the photoionization.Further work is required to understand the details of PL blinking withgreater certainty.Unusual PL blinking has been reported in strain-induced S-K GaAsQDs created from GaAs/A1GaAs QWs with InP stressor islands [71]. For asample with 140-nm-diameter InP stressor islands sitting on top of an outer100-A˚ barrier of A 10.3 Ga 0.7 As and a 30-A˚ GaAs QW beneath the barrier, thesurvey PL spectrum of the strain-induced QDs (SIQDs) following excitationat 488 nm (shown in Fig. 14) exhibits a number of well-defined peaks. Thesmall peak at 1.92 eV arises from the A1 0.3 Ga 0.7 As barriers. The peak at 1.75Figure 14 Photoluminescence spectra at 6.9 K of Stranski–Krastinow straininducedGaAs QDs. The left panel shows the PL spectra from a large number of straininducedQDs and includes peaks arising from the AlGaAs substrate, the GaAs QW,and the GaAs barrier; the right panel compares the broad PL spectrum from a largenumber of QDs with that from a single strain-induced GaAs QD. (From Ref. 71.)Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.