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Strong localization effect and carrier relaxation dynamics in self-assembled InGaN quantum dots emitting in the green.

Weng GE, Zhao WR, Chen SQ, Akiyama H, Li ZC, Liu JP, Zhang BP - Nanoscale Res Lett (2015)

Bottom Line: Strong localization effect in self-assembled InGaN quantum dots (QDs) grown by metalorganic chemical vapor deposition has been evidenced by temperature-dependent photoluminescence (PL) at different excitation power.The integrated emission intensity increases gradually in the range from 30 to 160 K and then decreases with a further increase in temperature at high excitation intensity, while this phenomenon disappeared at low excitation intensity.Using this model, the evolution of excitation-power-dependent emission intensity, shift of peak energy, and linewidth variation with elevating temperature is well explained.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Semiconductor Photonics Research Center, Xiamen University, 422 South Siming Road, Xiamen, 361005 P. R. China.

ABSTRACT
Strong localization effect in self-assembled InGaN quantum dots (QDs) grown by metalorganic chemical vapor deposition has been evidenced by temperature-dependent photoluminescence (PL) at different excitation power. The integrated emission intensity increases gradually in the range from 30 to 160 K and then decreases with a further increase in temperature at high excitation intensity, while this phenomenon disappeared at low excitation intensity. Under high excitation, about 40% emission enhancement at 160 K compared to that at low temperature, as well as a higher internal quantum efficiency (IQE) of 41.1%, was observed. A strong localization model is proposed to describe the possible processes of carrier transport, relaxation, and recombination. Using this model, the evolution of excitation-power-dependent emission intensity, shift of peak energy, and linewidth variation with elevating temperature is well explained. Finally, two-component decays of time-resolved PL (TRPL) with various excitation intensities are observed and analyzed with the biexponential model, which enables us to further understand the carrier relaxation dynamics in the InGaN QDs.

No MeSH data available.


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Temperature dependence of emission peak energies (a) and spectra linewidths (FWHM) (b) measured under different excitation power. The dashed lines are the fitting results using Varshni’s model.
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Fig2: Temperature dependence of emission peak energies (a) and spectra linewidths (FWHM) (b) measured under different excitation power. The dashed lines are the fitting results using Varshni’s model.

Mentions: The temperature dependences of PL experiments were performed on the QD sample over a temperature range of 5 to 300 K under different excitation power: 0.045 and 18.5 mW, respectively. By fitting the PL spectra with a Gauss peak, the emission peak energies, spectral linewidths [full width at half maximum (FWHM)], and emission intensities are determined. As shown in Figure 2a, both the peak energies (Ep) show an “S shape” (decrease-increase-decrease) variation with increasing temperature. Although this emission behavior is somewhat similar to those reported in InGaN QWs, the temperature of the turning point from blueshift to redshift (T = 260 K) is found much more higher, which is believed to be relevant to the more deeper localization potential in QDs. It is found that the S-shape variation behavior depends on excitation intensity. Under high excitation intensity (P = 18.5 mW), Ep is initially smaller (T = 5 K) and then quickly becomes larger at elevated temperature (T > 30 K), meaning a narrower variation range of the peak position in comparison with that under weak excitation (P = 0.045 mW). Another dissimilarity is that the blueshift starts at a lower temperature of 60 K for the high excitation. As discussed later, these behaviors are ascribed to the distinct carrier redistribution in localized state assemblies with increasing temperature.Figure 2


Strong localization effect and carrier relaxation dynamics in self-assembled InGaN quantum dots emitting in the green.

Weng GE, Zhao WR, Chen SQ, Akiyama H, Li ZC, Liu JP, Zhang BP - Nanoscale Res Lett (2015)

Temperature dependence of emission peak energies (a) and spectra linewidths (FWHM) (b) measured under different excitation power. The dashed lines are the fitting results using Varshni’s model.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4384949&req=5

Fig2: Temperature dependence of emission peak energies (a) and spectra linewidths (FWHM) (b) measured under different excitation power. The dashed lines are the fitting results using Varshni’s model.
Mentions: The temperature dependences of PL experiments were performed on the QD sample over a temperature range of 5 to 300 K under different excitation power: 0.045 and 18.5 mW, respectively. By fitting the PL spectra with a Gauss peak, the emission peak energies, spectral linewidths [full width at half maximum (FWHM)], and emission intensities are determined. As shown in Figure 2a, both the peak energies (Ep) show an “S shape” (decrease-increase-decrease) variation with increasing temperature. Although this emission behavior is somewhat similar to those reported in InGaN QWs, the temperature of the turning point from blueshift to redshift (T = 260 K) is found much more higher, which is believed to be relevant to the more deeper localization potential in QDs. It is found that the S-shape variation behavior depends on excitation intensity. Under high excitation intensity (P = 18.5 mW), Ep is initially smaller (T = 5 K) and then quickly becomes larger at elevated temperature (T > 30 K), meaning a narrower variation range of the peak position in comparison with that under weak excitation (P = 0.045 mW). Another dissimilarity is that the blueshift starts at a lower temperature of 60 K for the high excitation. As discussed later, these behaviors are ascribed to the distinct carrier redistribution in localized state assemblies with increasing temperature.Figure 2

Bottom Line: Strong localization effect in self-assembled InGaN quantum dots (QDs) grown by metalorganic chemical vapor deposition has been evidenced by temperature-dependent photoluminescence (PL) at different excitation power.The integrated emission intensity increases gradually in the range from 30 to 160 K and then decreases with a further increase in temperature at high excitation intensity, while this phenomenon disappeared at low excitation intensity.Using this model, the evolution of excitation-power-dependent emission intensity, shift of peak energy, and linewidth variation with elevating temperature is well explained.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Semiconductor Photonics Research Center, Xiamen University, 422 South Siming Road, Xiamen, 361005 P. R. China.

ABSTRACT
Strong localization effect in self-assembled InGaN quantum dots (QDs) grown by metalorganic chemical vapor deposition has been evidenced by temperature-dependent photoluminescence (PL) at different excitation power. The integrated emission intensity increases gradually in the range from 30 to 160 K and then decreases with a further increase in temperature at high excitation intensity, while this phenomenon disappeared at low excitation intensity. Under high excitation, about 40% emission enhancement at 160 K compared to that at low temperature, as well as a higher internal quantum efficiency (IQE) of 41.1%, was observed. A strong localization model is proposed to describe the possible processes of carrier transport, relaxation, and recombination. Using this model, the evolution of excitation-power-dependent emission intensity, shift of peak energy, and linewidth variation with elevating temperature is well explained. Finally, two-component decays of time-resolved PL (TRPL) with various excitation intensities are observed and analyzed with the biexponential model, which enables us to further understand the carrier relaxation dynamics in the InGaN QDs.

No MeSH data available.


Related in: MedlinePlus