Isoelectronic Centers in Quantum Dots and Photoluminescence Decay
It is hypothesized that Te forms an isoelectronic trap in ZnSe. These isoelectronic centers show blue and green band luminescence at low temperature. Quantum confinement effects reveal isoelectronic trap related luminescence at room temperature in contrast to bulk ZnSe1 − yTey. To find the effect of these isoelectronic center on Mn2+ d–d transition luminescence, Mn doped ZnSe0.99Te0.01 QDs are synthesized. Mn doped ZnSe shows dominating orange emission related to Mn2+ d–d transitions. This Mn emission increases at the cost of band edge emission. Addition of Te as small as 1 % in ZnSe strongly quenches photoluminescence of Mn-doped ZnSe QDs showing predominance of Te-isoelectronic centers. Orange emission and near band edge luminescence in Mn doped ZnSe0.99Te0.01 are not correlated as they are in case of Mn-doped ZnSe QDs. Time resolved photoluminescence and photoluminescence excitation study revealed these isoelectronic center changes the recombination path ways. The changes in relaxation path ways are responsible for distinct emission behavior of ZnSe0.99Te0.01QDs.
KeywordsQuantum dots Isoelectronic doping Luminescence Time resolved photoluminescence
KGS and CR are thankful to BRNS and ISRO-UOP for the financial support respectively. Authors are extremely thankful to Prof. N. Periasamy of TIFR for his interest in the work and several suggestions. We are also thankful to Ms. Madhuri of TIFR for help in recording the TRPL spectra. Authors are also thankful to D. S. T. Unit on Nanoscience, CNQS and D. S. T. FIST program for various characterization facilities.
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