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Accordingly, the increase of T is expected to give no Figure 4. RWL (a) measured for SQD at hIR = 1.240 eV, further increase of IQD. Consequently, the higher value of hex = 1.471 eV, P0 = 200 nW, PIR = 100 W for a number of single at low T is, the less T -induced increase of IQD is T s. Isingle and Isingle (b) measured for SQD at hex = 1.471 eV, WL QD predicted, which is nicely confirmed by the data shown in P0 = 200 nW, at different T s. single and dual (c) measured Fig. 3, b. These experimental findings are consistent with for SQD at hIR = 1.240 eV, hex = 1.471 eV, P0 = 200 nW, the temperature-induced behaviour of the Isingle revealed QD PIR = 100 W for a number of T s. The inset in (b) shows in ordinary (macro)-PL measurements: Isingle for low dot Isingle measured for SQD at hex = 1.410 eV, P0 = 17 W at QD QD density revealed an increase by 2 times as T was increased different T s.

, 2005, 47, . 2072 E.S. Moskalenko, K.F. Karlsson, V. Donchev, P.O. Holtz, W.V. Schoenfeld, P.M. Petroff 4. Conclusion An additional IR laser considerably quenches the QD PL signal. This is explained in terms of screening of the internal electric field by the extra holes created in the sample as a result of the IR excitation. The quenching effect progressively vanishes with increasing temperature as well as dot density. These observations are due to a considerably improved QDs collection efficiency at which the effect of electric field on the carrier transport in the plane of the WL becomes less important. The observed effects could be widely used in practice to effectively tune the QDs collection efficiency and manipulating the light emission intensity in QD-based optoelectronic devices.

Figure 5. RQD measured for sample spots with different dot density at T = 5K, hIR = 1.240 eV, hex = 1.471 eV, P0 = 200 nW, single PIR = 100 Wplotted for a number of MQDs. The inset shows References single RQD for SQDplotted for a number of SQD measured at different [1] L. Jacak, P. Hawrylak, A. Wojs. Quantum Dots. SpringerT s (taken from Fig. 4, c).

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respect to the case of SQD (Fig. 3, a) can also be explained [6] D. Bimberg, M. Grundmann, N.N. Ledentsov. Quantum Dot satisfactorily within the model proposed. In fact, with Heterostructures. Willey, London (1999). 328 p.

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becomes less important. This explains the essentially higher Appl. Phys. Lett. 70, 13, 27 (1997); J.M. Garcia, T. Mankad, values of RQDs of 0.5 and 0.9 measured at T = 5K for P.O. Holtz, P.J. Wellman, P.M. Petroff. Appl. Phys. Lett. 72, 24, MQDs 1 and MQDs 2, respectively compare to that of 0.3172 (1998); J.M. Garcia, G. Medeiros-Ribeiro, K. Schmidt, for the case of SQD (Fig. 3, a). In addition, the higher the T. Ngo, J.L. Feng, A. Lorke, J. Kotthaus, P.M. Petroff. Appl.

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