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Influence of Si-Doping on the Characteristics of
InGaN–GaN Multiple Quantum-Well Blue Light
Emitting Diodes
L. W. Wu, S. J. Chang, T. C. Wen, Y. K. Su, Senior Member, IEEE, J. F. Chen, Member, IEEE, W. C. Lai, C. H. Kuo,
C. H. Chen, and J. K. Sheu
IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 38, NO. 5, MAY 2002
Sum DJ
Outline
• Introduction
• Experiment
• Results and discussion
• Conclusion
• References
Introduction
• Low temperature will significantly
degrade the crystal quality of the GaN
barrier layers. Such a problem can be
overcome by introducing Si doping in
the GaN layers.
Experiment
p-GaN
Mg doped Al0.1Ga0.9N@1060ºC
n-GaN@ 1060ºC
GaN nucleation layer (30nm) @ 560ºC
Sapphire
MQW InGaN/GaN：3nm/10nm five periodes
@770ºC (Barrier doping Si 3×1017cm-3)
Results and discussion
Fig. 1. Typical room-temperature photoluminescence spectra of the MQW blue LED
structure with an unintentionally doped or Si-doped barrier. The photoluminescence peak
wavelength of the Si-doped barrier LED does not reveal significant blue shift due to
Coulomb screening of the internal electric field.
Results and discussion
Fig. 2. X-ray diffraction spectra of unintentionally doped or Si-doped barrier MQW
LED.
Results and discussion
Fig. 3. Typical I–V characteristics of forward bias for unintentionally doped
and Si-doped barrier LED. The forward voltage for the unintentionally doped
and Si-doped barrier LED is 4.52 and 3.5 V at 20-mA injection current.
Results and discussion
Fig. 4. Dynamic resistance depends on the applied voltage for the
unintentionally doped and Si-doped barrier LED at forward operation.
Results and discussion
Fig. 5. Dominated wavelength of electroluminescence spectra depends on the
injection current for the unintentionaly doped and Si-doped barrier LED.
Results and discussion
Fig. 6. Dlectroluminescence spectra of the unintentionally doped barrier and Si-doped barrier
LED at forward dc currents of 20 mA. The luminous intensity at forward dc currents of 20 mA
for the unintentionally doped barrier LED is 25.1 mcd. For the LED with the Si-doped barrier, the
luminous intensity is 36.1 mcd.
Conclusion
• Compared with unintentionally doped
samples, double crystal X-ray diffraction
(DCXRD) indicates that Si-doping in the
barrier layers can improve the crystal and
interfacial qualities of the InGaN–GaN MQW
LEDs.
Structural analysis of Si-doped AlGaN/GaN
multi-quantum wells
Tetsuya Nakamura, Shingo Mochizuki, Shinji Terao, Tomoaki Sano,
Motoaki Iwaya, Satoshi Kamiyama, Hiroshi Amanob,c, Isamu Akasaki
Journal of Crystal Growth 237–239 1129–1132(2002)
Outline
• Introduction
• Experiment
• Results and discussion
• Conclusion
• References
Introduction
• It was reported that Si doping improves
the optical properties of AlGaN/GaN
MQW and GaInN/GaN MQW.
Experiment
MQW Al0.07Ga0.93N/GaN：3nm/7nm five periodes
@770ºC (Barrier doping Si 3×1018 to 3×1018cm-3)
p-GaN
Mg doped A0.1Ga0.9N@1060ºC
GaN(1µm)@ 1100ºC
LT buffer layer
Sapphire
Results and discussion
undoped
4.2×1019cm-3
6 ×1018cm-3
9×1019cm-3
Fig. 1. AFM surface images for Al0.07Ga0.93N/GaN 5QW. Si concentration in barrier layer
was (a) undoped, (b) 6×1018 cm-3,(c) 4.2×1019 cm-3, and (d) 9×1019 cm-3.
Results and discussion
Fig. 2. Across-sectiona l TEM image for Al0.07Ga0.93N/GaN 5QW. Si
concentration in barrier layer was 9×1019 cm-3.
Results and discussion
5
2
4
6
3
1
Fig. 3. Relationship between the size of the V-shaped defects and Si
concentration.
Results and discussion
Al0.07Ga0.93N
barrier
Fig. 4. AFM surface images for Al0.07Ga0.93N
layer (a) and GaN layer (b) with Si
concentration of 4×1019 cm-3
Results and discussion
Fig. 5. PL maximum intensity and surface covering ratio of Vshaped defects as
a function of Si concentration.
Conclusion
• PL intensity gradually increases with Si
doping. But when the Si concentration
exceeds 4.2 × 1019 cm-3, PL intensity was
rapidly decreased with the formation of V
shaped defect.
Efficiency droop behaviors of InGaN/GaN multiplequantum-well light-emitting diodes with varying
quantum well thickness
Y.-L. Li, Y.-R. Huang, and Y.-H. Lai
APPLIED PHYSICS LETTERS 91, 181113 2007
Outline
• Introduction
• Experiment
• Results and discussion
• Conclusion
• References
Introduction
• Well-known fundamental problem needs
to be overcome, namely, the efficiency
“droop,” which is the reduction in
efficiency as the current is increased.
Experiment
Chips 350 ×350µm2
FIG. 1. Color online Schematic structure InGaN/GaN multiple-quantumwell
LEDs with varied well thicknesses.
Results and discussion
FIG. 2. Color online Temperaturevaried from 10 to 300 K photoluminescence
measurements for roomtemperature IQE assessment of InGaN/GaN MQW LEDs with
varied well thicknesses.
Results and discussion
FIG. 3. Color online Roomtemperature EL spectra of MQW LEDs with varied well thicknesses under
various injection currents. The peaks of the emission spectra shift toward shorter wavelengths blueshift
as the current is increased from 10 to 250 mA, as indicated by the two vertical lines.
Results and discussion
FIG. 4. Color online Normalized external quantum efficiency measurements of the MQW LEDs
with varied well thicknesses. Measurements are pulsed with 5% duty cycle. For samples with
different well thicknesses, the efficiency drop from the highest value at low current density to 200
A/cm2 is 2.7%, 17.9%, 36.7%, and 40.4%, respectively. This figure clearly illustrates a reduced
efficiency-droop effect for thicker quantum wells.
Conclusion
• We have demonstrated that the droop effect
can be drastically reduced to less than 5% at a
current density as high as 200 A/cm2.
整理
• 在barrier摻si 能介由Coulomb screening
減緩QCSE使得電子電洞波函數較為
重疊，但摻雜過多會影響磊晶品質。
• 減少well的厚度能使得電子電洞波函
數較為重疊，但過窄的well會突顯局
限能力不足的現象。
• barrier摻si會使得V-shaped defects有面
積變小、深度變深的效應。
References
•
•
•
L. W. Wu, S. J. Chang, T. C. Wen, Y. K. Su, Senior Member, IEEE, J. F.
Chen, Member, IEEE, W. C. Lai, C. H. Kuo,C. H. Chen, and J. K.
Sheu“Influence
of
Si-Doping
on
the
Characteristics
of
InGaN–GaN
Multiple
Quantum-Well
Blue
Light
Emitting Diodes” IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL.
38, NO. 5, MAY 2002 .
Tetsuya Nakamura, Shingo Mochizuki, Shinji Terao, Tomoaki Sano,
Motoaki Iwaya, Satoshi Kamiyama, Hiroshi Amanob,c, Isamu
Akasaki“Structural
analysis
of
Si-doped
AlGaN/GaN
multi-quantum wells ” Journal of Crystal Growth 237–239 1129–
1132(2002) .
Y.-L. Li, Y.-R. Huang, and Y.-H. Lai“Efficiency droop behaviors of
InGaN/GaN multiple-quantum-well light-emitting diodes with varying
quantum well thickness ” APPLIED PHYSICS LETTERS 91, 181113 2007 .
• Thanks for your attention !