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2015/04/16
S.S.H
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Outline
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Introduction
Experiments
Results and Discussion
Conclusion
References
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Introduction
• However, the issue of efficiency droop has an impediment to the
developing of high power devices. Recently, it has been reported that
the electron leakage and low efficiency of hole injection are the
primary reasons to cause the issue.
• In conventional LEDs, strong electrostatic field generated by the
spontaneous and piezoelectric polarization will lead to severe bandbending, and this deformed conductive band can aggravate the
electrons spill over from the p-type layer.
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Introduction
• In InGaN/GaN quantum wells (QWs) LEDs, holes have a large
effective mass and hence low mobility, which makes it hard to
inject into the MQWs. On the contrary, electrons can escape from
the MQWs easily due to the small effective mass.
• Therefore, a specific design of the quantum barrier next to p-type
layer, which is called last quantum barrier(LQB) is expected to
improve the characteristics of LEDs. Some suggestions, such as a
p-doped GaN LQB and the graded LQB, have been proposed to
promote the efficiency.
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Experiments
chip size 300 × 300 μm2
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Results and Discussion
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Results and Discussion
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Results and Discussion
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Results and Discussion
3.19ev
3.13ev
3.27ev
435nm
328mw
224mw
80mw
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Conclusion
• In summary, LEDs with GSL LQB exhibit an improved
efficiency droop and superior optical properties compared with
the conventional LEDs.
• A series of deep potential wells formed by the superlattice
between the last quantum well and electron blocking layer can
effectively alleviate the strong electrostatic fields, leading to a
enhancement of hole injection and the electron confinement.
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References
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Thank you for your attention
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