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Y.Y CHEN
Outline
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Introduction
Experiment
Results and discussion
Conclusion
References
Introduction
• In general, the light output for a multiple quantum well
(MQW) light-emitting diode (LED) depends on the
internal quantum efficiency (IQE) and the light extraction
efficiency (LEE) . The former case mainly depends on the
quality of materials and their heterointerfaces within the
active region. In addition, the quality of the layer interfaces
below and above the active region would also affect LED
performance.
Introduction
• To achieve a smooth n-GaN surface morphology, a high
growth temperature and a V/III (group V-to-group III)
molar gas-phase concentration ratio are often adopted.
• In addition, the quantum efficiency of LEDs is also
dependent on the current spreading effect on the LEDs.
• In general, most interests in the topics of current spreading
(CS) for the GaN-based LEDs are focused on the p-type
top contact layers including transparent conductive oxides.
Introduction
• Except for the top CS layer, a bottom CS layer positioned
between the substrate and the active layer of a LED is also
an important issue to further improve the current spreading
performance.
• In this study, an Si-doped InGaN layer was placed between
the n-GaN buffer (i.e., cladding) and the active layers. The
InGaN insertion layer plays the role of a current-spreading
layer and/or a smoothing layer. The related results which
focus on the electrical and optical properties of the
fabricated LEDs will be discussed subsequently.
Experiment
LED I
wafers were thinned down to 90μm
Chip size: 250*575μm2
820℃
carrier concentration
1*1018
Results and discussion
18.1mW
15.3mW
Conclusion
• In conclusion, GaN-based blue LEDs using the InGaN
insertion layer between the n-type GaN cladding layer and
the active layer (InGaN/GaN multiple quantum well) can
effectively improve device performances including the
endurance of ESD and light output power. Based on the
aforesaid chraracterizations,we would like to suggest that
the better current spreading effect is the dominant factor
for contributing to the improvement of device performance.
References
• J. K. Sheu, J. M. Tsai, S. C. Shei, W. C. Lai, T. C.Wen, C. H.Kou, Y.
K.Su, S. J. Chang, and G. C. Chi, “Low-operation voltage of
InGaN/GaN light-emitting diodes with Si-doped
Short-period
superlattice tunneling contact layer,” IEEE Electron Device Lett., vol.
22, no. 10, pp. 460–462, Oct. 2001.
• E.-H. Park, J. Jang, S. Gupta, I. Ferguson, S.-K. Jeon, J.-G. Lim, J.-S.
Lee, C.-H. Kim, and J.-S. Park, “The effect of the last quantum barrier
on the internal quantum efficiencyof InGaN-light emitting diode,”
Appl. Phys. Lett., vol. 93, p. 101112, 2008, and references therein.
Thank you for your attention