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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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Schematic diagram of the QD epitaxial structure.
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Fig1: Schematic diagram of the QD epitaxial structure.

Mentions: The InGaN self-assembled QD sample investigated in this work was epitaxially grown on a (0001)-oriented sapphire by MOCVD system [22]. A schematic diagram of the QD epitaxial structure is shown in Figure 1. The active region consisted of two pairs of InGaN/GaN QDs. The GaN cap layers on QDs were deposited using a two-step method: firstly, a 2-nm-thick low-temperature grown GaN matrix layer was deposited at the same growth temperature (670°C) of QDs to protect them during subsequent temperature ramping process, then the temperature was ramped to 850°C, and finally, a 8-nm-thick GaN barrier layer was grown. The indium content of the QDs is about 27%. Other detailed growth procedures are available in ref. [22]. Cross-section Z-contrast scanning transmission electron microscopy (STEM) shows that the diameters of the QDs range from 20 to 60 nm, while the average height of QDs is about 2.5 nm.Figure 1


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)

Schematic diagram of the QD epitaxial structure.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig1: Schematic diagram of the QD epitaxial structure.
Mentions: The InGaN self-assembled QD sample investigated in this work was epitaxially grown on a (0001)-oriented sapphire by MOCVD system [22]. A schematic diagram of the QD epitaxial structure is shown in Figure 1. The active region consisted of two pairs of InGaN/GaN QDs. The GaN cap layers on QDs were deposited using a two-step method: firstly, a 2-nm-thick low-temperature grown GaN matrix layer was deposited at the same growth temperature (670°C) of QDs to protect them during subsequent temperature ramping process, then the temperature was ramped to 850°C, and finally, a 8-nm-thick GaN barrier layer was grown. The indium content of the QDs is about 27%. Other detailed growth procedures are available in ref. [22]. Cross-section Z-contrast scanning transmission electron microscopy (STEM) shows that the diameters of the QDs range from 20 to 60 nm, while the average height of QDs is about 2.5 nm.Figure 1

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