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  • Editor: Christian Seassal
  • Vol. 22, Iss. S3 — May. 5, 2014
  • pp: A633–A641
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Optoelectrical characteristics of green light-emitting diodes containing thick InGaN wells with digitally grown InN/GaN

Chun-Ta Yu, Wei-Chih Lai, Cheng-Hsiung Yen, Hsu-Cheng Hsu, and Shoou-Jinn Chang  »View Author Affiliations


Optics Express, Vol. 22, Issue S3, pp. A633-A641 (2014)
http://dx.doi.org/10.1364/OE.22.00A633


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Abstract

Compared with conventionally grown thin InGaN wells, thick InGaN wells with digitally grown InN/GaN exhibit superior optical properties. The activation energy (48 meV) of thick InGaN wells (generated by digital InN/GaN growth from temperature-dependent integrated photoluminescence intensity) is larger than the activation energy (25 meV) of conventionally grown thin InGaN wells. Moreover, thick InGaN wells with digitally grown InN/GaN exhibit a smaller σ value (the degree of localization effects) of 19 meV than that of conventionally grown thin InGaN wells (23 meV). Compared with green light-emitting diodes (LEDs) with conventional thin InGaN wells, the improvement in 20-A/cm2 output power for LEDs containing thick InGaN wells with digitally grown InN/GaN is approximately 23%.

© 2014 Optical Society of America

1. Introduction

Considerable progress has been achieved in the design and fabrication of GaN-based light-emitting diodes (LEDs), particularly for LEDs using InGaN/GaN multiple quantum wells (MQWs) as active regions [1

1. S. Nakamura, T. Mukai, and M. Senoh, “Candela-class high-brightness InGan/AlGaN double-heterostructure blue-light-emitting diodes,” Appl. Phys. Lett. 64(13), 1687–1689 (1994). [CrossRef]

3

3. S. J. Chang, C. H. Kuo, Y. K. Su, L. W. Wu, J. K. Sheu, T. C. Wen, W. C. Lai, J. F. Chen, and J. M. Tsai, “400-nm InGaN-GaN and InGaN-AlGaN multiquantum well light-emitting diodes,” IEEE J. Sel. Top. Quantum Electron. 8(4), 744–748 (2002). [CrossRef]

]. To enhance luminous efficiency, significant effort has been exerted to improve the material quality [4

4. S. Nakamura, N. Senoh, N. Iwasa, and S. I. Nagahama, “High-brightness InGaN blue, green and yellow light-emitting diodes with quantum well structures,” Jpn. J. Appl. Phys. Part 2 34(7A), L797–L799 (1995).

,5

5. T. Mukai, S. Nagahama, M. Sano, T. Yanamoto, D. Morita, T. Mitani, Y. Narukawa, S. Yamamoto, I. Niki, M. Yamada, S. Sonobe, S. Shioji, K. Deguchi, T. Naitou, H. Tamaki, Y. Murazaki, and M. Kameshima, “Recent progress of nitride-based light emitting devices,” Phys. Status Solidi A 200(1), 52–57 (2003). [CrossRef]

], light-extraction efficiency [6

6. J. K. Kim, T. Gessmann, E. F. Schubert, J. Q. Xi, H. Luo, J. Cho, C. Sone, and Y. Park, “GaInN light-emitting diode with conductive omnidirectional reflector having a low-refractive-index indium-tin oxide layer,” Appl. Phys. Lett. 88(1), 013501 (2006). [CrossRef]

], and metal-semiconductor ohmic contacts [7

7. Y.-L. Li, E. F. Schubert, J. W. Graff, A. Osinsky, and W. F. Schaff, “Low-resistance ohmic contacts to p-type GaN,” Appl. Phys. Lett. 76(19), 2728–2730 (2000). [CrossRef]

] of blue LEDs. InGaN-based blue LEDs can achieve external quantum efficiency of more than 70% [8

8. M. R. Krames, O. B. Shchekin, R. Mueller-Mach, G. Mueller, L. Zhou, G. Harbers, and M. G. Craford, “Status and future of high-power light-emitting diodes for solid-state lighting,” IEEE J. Display Technol. 3(2), 160–175 (2007). [CrossRef]

,9

9. J. M. Phillips, M. E. Coltrin, M. H. Crawford, A. J. Fischer, M. R. Krames, R. Mueller-Mach, G. O. Mueller, Y. Ohno, L. E. S. Rohwer, J. A. Simmons, and J. Y. Tsao, “Research challenges to ultra-efficient inorganic solid-state lighting,” Laser Photonics Rev. 1(4), 307–333 (2007). [CrossRef]

]. However, the quantum efficiency of InGaN-based LEDs is significantly lower in the green to yellow (500-nm to 580-nm) spectral range, which is known as the “green-yellow gap” [8

8. M. R. Krames, O. B. Shchekin, R. Mueller-Mach, G. Mueller, L. Zhou, G. Harbers, and M. G. Craford, “Status and future of high-power light-emitting diodes for solid-state lighting,” IEEE J. Display Technol. 3(2), 160–175 (2007). [CrossRef]

,9

9. J. M. Phillips, M. E. Coltrin, M. H. Crawford, A. J. Fischer, M. R. Krames, R. Mueller-Mach, G. O. Mueller, Y. Ohno, L. E. S. Rohwer, J. A. Simmons, and J. Y. Tsao, “Research challenges to ultra-efficient inorganic solid-state lighting,” Laser Photonics Rev. 1(4), 307–333 (2007). [CrossRef]

]. Therefore, for applications involving white LEDs with direct mixing of blue, green, and red lights, a high number of InGaN-based green LEDs are required to match the high-efficiency InGaN-based blue LEDs. For InGaN wells, green GaN-based LEDs require a high-In mole fraction, which results in an enlargement in the lattice-mismatch-induced strain of InGaN wells. V-shaped defects are easily formed in high-In MQWs and are triggered by threading dislocations in the buffer layer. These defects are formed because of strain relaxation associated with stacking faults or In segregation, and such defects typically terminate on the sample surface with V-shaped defects [10

10. X. H. Wu, C. R. Elsass, A. Abare, M. Mack, S. Keller, P. M. Petroff, S. P. DenBaars, J. S. Speck, and S. J. Rosner, “Structural origin of V-defects and correlation with localized excitonic centers in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 72(6), 692–694 (1998). [CrossRef]

15

15. Y. Chen, T. Takeuchi, H. Amano, I. Akasaki, N. Yamada, Y. Kaneko, and S. Y. Wang, “Pit formation in GaInN quantum wells,” Appl. Phys. Lett. 72(6), 710–712 (1998). [CrossRef]

]. These defects can degrade the efficiency of GaN-based green LEDs. Recently, several studies have considered improving the interface abruptness and optical properties of green LEDs using trimethylindium (TMIn) preflow prior to the growth of InGaN quantum wells [16

16. S. J. Leem, M. H. Kim, J. Shin, Y. Choi, and J. Jeong, “The effects of In flow during growth interruption on the optical properties of InGaN multiple quantum wells grown by low pressure metalorganic chemical vapor deposition,” Jpn. J. Appl. Phys. Part 2 40(4B), L371–L373 (2001).

20

20. S. W. Feng, C. Y. Tsai, H. C. Wang, H. C. Lin, and J. I. Chyi, “Optical properties of InGaN/GaN multiple quantum wells with trimethylindium treatment during growth interruption,” J. Cryst. Growth 325(1), 41–45 (2011). [CrossRef]

]. TMIn preflow results in smooth InGaN well surfaces, decreases V-shaped defects in InGaN/GaN MQWs [18

18. H. C. Lin, R. S. Lin, and J. I. Chyi, “Enhancing the quantum efficiency of InGaN green light-emitting diodes by trimethylindium treatment,” Appl. Phys. Lett. 92(16), 161113 (2008). [CrossRef]

], and improves the emission efficiency of InGaN/GaN MQW green LEDs. Moreover, several studies have also reported enhancements in surface migration of adatoms during the growth of III-nitride alloys using digital techniques [21

21. J. P. Zhang, E. Kuokstis, Q. Fareed, H. Wang, J. W. Yang, G. Simin, M. Asif Khan, R. Gaska, and M. S. Shur, “Pulsed atomic layer epitaxy of quaternary AlInGaN layers,” Appl. Phys. Lett. 79(7), 925–927 (2001). [CrossRef]

,22

22. S. Choi, H. J. Kim, J.-H. Ryou, and R. D. Dupuis, “Digitally alloyed modulated precursor flow epitaxial growth of AlxGa1−xN layers with AlN and AlyGa1−yN monolayers,” J. Cryst. Growth 311(12), 3252–3256 (2009). [CrossRef]

]. In the present study, we demonstrate efficiency-improved green LEDs containing thick InGaN wells with digitally grown InN/GaN. We discuss the optical characteristics of thick InGaN wells with digitally grown InN/GaN in the InGaN/GaN MQW region. In addition, we discuss the effect of digital InN/GaN growth in thick InGaN wells on the characteristics and fabrication process of InGaN/GaN MQW green LEDs.

2. Experiments

3. Results and discussion

The measured and simulated X-ray θ−2θ diffraction (XRD) spectra of LEDs I and II are shown in Fig. 2.
Fig. 2 θ-2θ scan X-ray diffraction spectra of LEDs (a) I and (b) II. The satellite peaks are labeled with numbers. The lower curve is the simulation resulting from fitting the XRD data.
The XRD spectra of both LEDs I and II exhibit distinct satellite peaks, which indicate the abrupt interfaces between the InGaN wells and the GaN barrier layers of green InGaN/GaN MQWs. The XRD results indicate that the period thickness of green InGaN/GaN MQWs containing either InGaN wells with digitally grown InN/GaN or conventional wells is approximately 19 nm. The full-width half maxima (FWHM) of the −1-order satellite peaks of LEDs I and II are 93.5” and 89”, respectively. The broadening of the FWHM of the satellite peaks is attributed to the interface roughness or to fluctuations in the alloy composition [23

23. Y. H. Cho, F. Fedler, R. J. Hauenstein, G. H. Park, J. J. Song, S. Keller, U. K. Mishra, and S. P. Denbaars, “High resolution x-ray analysis of pseudomorphic InGaN/GaN multiple quantum wells: Influence of Si doping concentration,” J. Appl. Phys. 85(5), 3006–3008 (1999). [CrossRef]

]. Compared with LED I, LED II presents a −1-order satellite peak with a smaller FWHM. Therefore, the structural properties and the compositional abruptness of LED II were remarkably improved as a result of digital InN/GaN growth for InGaN wells. The In composition of the InGaN well is obtained by fitting the XRD data, and the In contents in LEDs I and II are 27.5% and 16.7%, respectively. Compared with conventional InGaN wells, digital InN/GaN growth reduces the In content in InGaN by nearly half.
Fig. 3 TEM images of the InGaN/GaN MQWs for LEDs (a) I and (b) II.
Figure 3 shows transmission electron microscopy (TEM) images of the InGaN/GaN MQWs of LEDs I and II. The period thickness values of the InGaN/GaN pair of LEDs I and II are 21.5 nm and 22.8 nm, respectively. However, the thickness of the InGaN wells in LED II (7.2 nm) is found to be more than two times the thickness in LED I (3.3 nm).

Furthermore, the InGaN/GaN MQWs containing thick InGaN wells with digitally grown InN/GaN have clearer interfaces between InGaN wells and GaN barriers than conventionally grown InGaN/GaN MQWs, and this finding is consistent with the XRD results. The morphology of InGaN/GaN MQW samples with and without digitally grown InN/GaN in thick InGaN wells was studied by atomic force microscopy (AFM). The pit density from AFM images (not shown here) of the InGaN/GaN MQWs containing thick InGaN wells with digitally grown InN/GaN (1.8 × 108 cm−2) is less than the pit density of the InGaN/GaN MQWs with conventional InGaN wells (2.9 × 108 cm−2). Furthermore, InGaN/GaN MQWs containing thick InGaN wells with digitally grown InN/GaN have less surface roughness (10.6 nm) than InGaN/GaN MQWs with conventional InGaN wells (16.2 nm). Therefore, compared with conventional InGaN/GaN MQWs, InGaN/GaN MQWs containing thick InGaN wells with digitally grown InN/GaN show superior crystal quality.

A photoluminescence (PL) measurement was performed on both LED samples to study their optical characteristics using a 25-mW HeCd laser as the excitation source. The room temperature (RT) PL spectra of both LEDs are shown in Fig. 4.
Fig. 4 RT PL spectra of LEDs I and II.
The PL emission peak wavelength of both LEDs is approximately 506 nm. The FWHM of the PL spectrum of LED II (20.2 nm) is less than the FWHM for LED I (22.0 nm). Similarly, the PL peak intensity of LED I is less than the PL peak intensity of LED II. The enhanced intensity and reduced PL FWHM of LED II can be attributed to the improved crystal quality of green InGaN/GaN MQWs containing thick InGaN wells with digitally grown InN/GaN. Although LED II presents a 16.7% In content in its InGaN wells, an InGaN well more than 7 nm thick can push the emission wavelength to 511 nm, which approaches the emission wavelength of LED I. The emission wavelength is sensitive to the In content, and the well thickness is also affected. We have simulated both a conventional well and a thick well using APSYS software. The result shows that the wavelengths of LED I and II are about 510 and 520 nm, although this result is not shown here. This simulation result is quite similar to our experiment’s findings.

Temperature-dependent PL measurements were performed on both samples to determine the temperature dependence of the peak energy and integrated intensity for the InGaN/GaN MQWs of LEDs I and II. The temperature dependence of the PL spectrum peak positions for LEDs I and II is shown in Fig. 5.
Fig. 5 PL spectrum peak position and FWHM with respect to temperature for LEDs I and II. The solid lines are fitted to the experimental data points using Eq. (1).
The PL spectrum peak positions for both samples exhibit a blueshift within the temperature range of 75 K to 200 K and also present an S-shaped curve with respect to temperature. This finding does not agree with the semiconductor band gap behavior predicted by the Varshni [24

24. Y. P. Varshni, “Temperature dependence of the energy gap in semiconductors,” Physica 34(1), 149–154 (1967). [CrossRef]

] or the Bose-Einstein [25

25. L. Viña, S. Logothetidis, and M. Cardona, “Temperature dependence of the dielectric function of germanium,” Phys. Rev. B 30(4), 1979–1991 (1984). [CrossRef]

] formula. The temperature-induced blueshifts of LEDs I and II (shown in Fig. 5) are approximately 17 meV and 15 meV, respectively. However, for LEDs I and II, the curves of the PL spectrum peak position with respect to temperature in the high-temperature region can be fitted using the formula reported by Eliseev et al. [26

26. P. G. Eliseev, P. Perlin, J. Lee, and M. Osinski, “Blue temperature-induced shift and band-tail emission in InGaN-based light sources,” Appl. Phys. Lett. 71(5), 569–571 (1997). [CrossRef]

], which is a combination of the Varshni formula and the band-tail model:
E=E(0)αT2β+Tσ2kBT,
(1)
where T is the temperature in Kelvin. The first term describes the energy gap at zero temperature, and α and β are known as Varshni’s fitting parameters. The third term is obtained from the localization effect, in which σ indicates the degree of the localization effect. A large value of σ indicates a strong localization effect. Boltzmann’s constant is kB. From fitting the equation to the experimental data, the values of σ obtained for LEDs I and II are 23 meV and 19 meV, respectively. LED I exhibits a larger σ than does LED II, and this difference implies a wide energy-scale distribution for band potential profile fluctuations. In InGaN/GaN MQW heterostructures, In compositional inhomogeneity has been proposed as the origin of the localization effect [27

27. S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, “Spontaneous emission of localized excitons in InGaN single and multiquantum well structures,” Appl. Phys. Lett. 69(27), 4188–4190 (1996). [CrossRef]

,28

28. Y. Narukawa, Y. Kawakami, M. Funato, S. Fujita, S. Fujita, and S. Nakamura, “Role of self-formed InGaN quantum dots for exaction localization in the purple laser diode emitting at 420 nm,” Appl. Phys. Lett. 70(8), 981–983 (1997). [CrossRef]

]. The inhomogeneity size of nanocrystallites in InGaN/GaN heterosystems causes potential fluctuations capable of spatially localizing excitations. The larger σ value of LED I can be attributed to the high In content of conventionally grown thin InGaN wells, which can lead to more severe composition inhomogeneity and thickness variation than observed in LED II.

Figure 5 also plots the temperature-dependent PL FWHM. At a low temperature, carriers are randomly located within the potential minima. As the temperature increases, carriers are thermally activated and redistributed into the lowest potential minima while the FWHM decreases. When temperature increases, the carriers populate higher-energy states as the FWHM increases. LED I has a larger FWHM than does LED II at low temperatures. The larger value of the FWHM at low temperatures indicates a more inhomogeneous distribution [29

29. F. B. Naranjo, M. A. Sánchez-García, F. Calle, E. Calleja, B. Jenichen, and K. H. Ploog, “Strong localization in InGaN layers with high In content grown by molecular-beam epitaxy,” Appl. Phys. Lett. 80(2), 231–233 (2002). [CrossRef]

].

Thus far, we have observed the superior optical properties of thick InGaN wells with digitally grown InN/GaN compared with conventionally grown thin InGaN wells. We have also fabricated LED chips to ascertain the light output power of LEDs I and II. The 20-A/cm2 forward voltages (Vf) of LEDs I and II are 3.35 V and 3.34 V, respectively. The reverse leakage currents at −15 V of LEDs I and II are 53.7 µA and 4.1 µA, respectively. The lower −15 V reverse leakage current of LED II can be attributed to the improved crystal quality of green InGaN/GaN MQWs containing thick InGaN wells with digitally grown InN/GaN.

We also investigated the relationship between emission wavelength and injection current density (as shown in Fig. 8).
Fig. 8 Emission wavelength with respect to injection current density for LEDs I and II.
LED II has a larger blueshift in its emission wavelength (the emission wavelength difference between the injection current of 1 and 60 A/cm2); for LED II, the blueshift is 15.5 nm, while the blueshift for LED I is 10.6 nm. With increasing injection current, the emission wavelength blueshift of GaN-based green LEDs could result from the quantum-confined Stark effect (QCSE) and the band-filling effect of the InGaN wells. Both thick InGaN wells with digitally grown InN/GaN and conventional InGaN wells show the localization effect. The band filling of the localized state in wells leads to the blueshift in the emission wavelength for both LEDs as injection current increases. However, the thick InGaN wells with digitally grown InN/GaN are about two times thicker than conventional InGaN wells. Therefore, the QCSE could be the dominant factor causing the heightened blueshift of the LEDs containing thick wells with digitally grown InN/GaN in comparison with conventional InGaN wells.

LED II notably demonstrates a larger 20-A/cm2 output power than that of LED I despite its thicker InGaN wells. The improved 20-A/cm2 light output power of LEDs containing thick InGaN wells with digitally grown InN/GaN should be attributed to the improved crystal quality and larger carrier delocalization energy of thick InGaN wells, which is achieved by digitally growing InN/GaN at relatively low growth temperatures. The results for the comparison between the light output powers of LEDs I and II are consistent with the results for the aforementioned optical properties.

4. Conclusion

Acknowledgments

The authors are grateful to the National Science Council of Taiwan for their financial support under Contract Nos. NSC101-2221-E-006-066-MY3 and 102-3113-P-009-007-CC2. This research was also made possible by the Advanced Optoelectronic Technology Center, National Cheng Kung University (as a project of the Ministry of Education of Taiwan), and by the financial support of the Bureau of Energy, Ministry of Economic Affairs of Taiwan, under Contract No. 102-E0603.

References and links

1.

S. Nakamura, T. Mukai, and M. Senoh, “Candela-class high-brightness InGan/AlGaN double-heterostructure blue-light-emitting diodes,” Appl. Phys. Lett. 64(13), 1687–1689 (1994). [CrossRef]

2.

S. J. Chang, W. C. Lai, Y. K. Su, J. F. Chen, C. H. Liu, and U. H. Liaw, “InGaN-GaN multiquantum-well blue and green light-emitting diodes,” IEEE J. Sel. Top. Quantum Electron. 8(2), 278–283 (2002). [CrossRef]

3.

S. J. Chang, C. H. Kuo, Y. K. Su, L. W. Wu, J. K. Sheu, T. C. Wen, W. C. Lai, J. F. Chen, and J. M. Tsai, “400-nm InGaN-GaN and InGaN-AlGaN multiquantum well light-emitting diodes,” IEEE J. Sel. Top. Quantum Electron. 8(4), 744–748 (2002). [CrossRef]

4.

S. Nakamura, N. Senoh, N. Iwasa, and S. I. Nagahama, “High-brightness InGaN blue, green and yellow light-emitting diodes with quantum well structures,” Jpn. J. Appl. Phys. Part 2 34(7A), L797–L799 (1995).

5.

T. Mukai, S. Nagahama, M. Sano, T. Yanamoto, D. Morita, T. Mitani, Y. Narukawa, S. Yamamoto, I. Niki, M. Yamada, S. Sonobe, S. Shioji, K. Deguchi, T. Naitou, H. Tamaki, Y. Murazaki, and M. Kameshima, “Recent progress of nitride-based light emitting devices,” Phys. Status Solidi A 200(1), 52–57 (2003). [CrossRef]

6.

J. K. Kim, T. Gessmann, E. F. Schubert, J. Q. Xi, H. Luo, J. Cho, C. Sone, and Y. Park, “GaInN light-emitting diode with conductive omnidirectional reflector having a low-refractive-index indium-tin oxide layer,” Appl. Phys. Lett. 88(1), 013501 (2006). [CrossRef]

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Y.-L. Li, E. F. Schubert, J. W. Graff, A. Osinsky, and W. F. Schaff, “Low-resistance ohmic contacts to p-type GaN,” Appl. Phys. Lett. 76(19), 2728–2730 (2000). [CrossRef]

8.

M. R. Krames, O. B. Shchekin, R. Mueller-Mach, G. Mueller, L. Zhou, G. Harbers, and M. G. Craford, “Status and future of high-power light-emitting diodes for solid-state lighting,” IEEE J. Display Technol. 3(2), 160–175 (2007). [CrossRef]

9.

J. M. Phillips, M. E. Coltrin, M. H. Crawford, A. J. Fischer, M. R. Krames, R. Mueller-Mach, G. O. Mueller, Y. Ohno, L. E. S. Rohwer, J. A. Simmons, and J. Y. Tsao, “Research challenges to ultra-efficient inorganic solid-state lighting,” Laser Photonics Rev. 1(4), 307–333 (2007). [CrossRef]

10.

X. H. Wu, C. R. Elsass, A. Abare, M. Mack, S. Keller, P. M. Petroff, S. P. DenBaars, J. S. Speck, and S. J. Rosner, “Structural origin of V-defects and correlation with localized excitonic centers in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 72(6), 692–694 (1998). [CrossRef]

11.

H. K. Cho, J. Y. Lee, G. M. Yang, and C. S. Kim, “Formation mechanism of V defects in the InGaN/GaN multiple quantum wells grown on GaN layers with low threading dislocation density,” Appl. Phys. Lett. 79(2), 215–217 (2001). [CrossRef]

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15.

Y. Chen, T. Takeuchi, H. Amano, I. Akasaki, N. Yamada, Y. Kaneko, and S. Y. Wang, “Pit formation in GaInN quantum wells,” Appl. Phys. Lett. 72(6), 710–712 (1998). [CrossRef]

16.

S. J. Leem, M. H. Kim, J. Shin, Y. Choi, and J. Jeong, “The effects of In flow during growth interruption on the optical properties of InGaN multiple quantum wells grown by low pressure metalorganic chemical vapor deposition,” Jpn. J. Appl. Phys. Part 2 40(4B), L371–L373 (2001).

17.

M. S. Kumar, J. Y. Park, Y. S. Lee, S. J. Chung, C.-H. Hong, and E.-K. Suh, “Improved internal quantum efficiency of green emitting InGaN/GaN multiple quantum wells by In preflow for InGaN well growth,” Jpn. J. Appl. Phys. 47(2), 839–842 (2008). [CrossRef]

18.

H. C. Lin, R. S. Lin, and J. I. Chyi, “Enhancing the quantum efficiency of InGaN green light-emitting diodes by trimethylindium treatment,” Appl. Phys. Lett. 92(16), 161113 (2008). [CrossRef]

19.

Y. J. Lee, Y. C. Chen, C. J. Lee, C. M. Cheng, S. W. Chen, and T. C. Lu, “Stable temperature characteristics and suppression of efficiency droop in InGaN Green light-emitting diodes using pre-TMIn flow treatment,” IEEE Photonics Technol. Lett. 22(17), 1279–1281 (2010). [CrossRef]

20.

S. W. Feng, C. Y. Tsai, H. C. Wang, H. C. Lin, and J. I. Chyi, “Optical properties of InGaN/GaN multiple quantum wells with trimethylindium treatment during growth interruption,” J. Cryst. Growth 325(1), 41–45 (2011). [CrossRef]

21.

J. P. Zhang, E. Kuokstis, Q. Fareed, H. Wang, J. W. Yang, G. Simin, M. Asif Khan, R. Gaska, and M. S. Shur, “Pulsed atomic layer epitaxy of quaternary AlInGaN layers,” Appl. Phys. Lett. 79(7), 925–927 (2001). [CrossRef]

22.

S. Choi, H. J. Kim, J.-H. Ryou, and R. D. Dupuis, “Digitally alloyed modulated precursor flow epitaxial growth of AlxGa1−xN layers with AlN and AlyGa1−yN monolayers,” J. Cryst. Growth 311(12), 3252–3256 (2009). [CrossRef]

23.

Y. H. Cho, F. Fedler, R. J. Hauenstein, G. H. Park, J. J. Song, S. Keller, U. K. Mishra, and S. P. Denbaars, “High resolution x-ray analysis of pseudomorphic InGaN/GaN multiple quantum wells: Influence of Si doping concentration,” J. Appl. Phys. 85(5), 3006–3008 (1999). [CrossRef]

24.

Y. P. Varshni, “Temperature dependence of the energy gap in semiconductors,” Physica 34(1), 149–154 (1967). [CrossRef]

25.

L. Viña, S. Logothetidis, and M. Cardona, “Temperature dependence of the dielectric function of germanium,” Phys. Rev. B 30(4), 1979–1991 (1984). [CrossRef]

26.

P. G. Eliseev, P. Perlin, J. Lee, and M. Osinski, “Blue temperature-induced shift and band-tail emission in InGaN-based light sources,” Appl. Phys. Lett. 71(5), 569–571 (1997). [CrossRef]

27.

S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, “Spontaneous emission of localized excitons in InGaN single and multiquantum well structures,” Appl. Phys. Lett. 69(27), 4188–4190 (1996). [CrossRef]

28.

Y. Narukawa, Y. Kawakami, M. Funato, S. Fujita, S. Fujita, and S. Nakamura, “Role of self-formed InGaN quantum dots for exaction localization in the purple laser diode emitting at 420 nm,” Appl. Phys. Lett. 70(8), 981–983 (1997). [CrossRef]

29.

F. B. Naranjo, M. A. Sánchez-García, F. Calle, E. Calleja, B. Jenichen, and K. H. Ploog, “Strong localization in InGaN layers with high In content grown by molecular-beam epitaxy,” Appl. Phys. Lett. 80(2), 231–233 (2002). [CrossRef]

30.

M. Leroux, N. Grandjean, B. Beaumont, G. Nataf, F. Semond, J. Massies, and P. Gibart, “Temperature quenching of photoluminescence intensities in undoped and doped GaN,” J. Appl. Phys. 86(7), 3721–3728 (1999). [CrossRef]

31.

E. Monroy, N. Gogneau, F. Enjalbert, F. Fossard, D. Jalabert, E. Bellet-Amalric, L. Si Dang, and B. Daudin, “Molecular-beam epitaxial growth and characterization of quaternary III–nitride compounds,” J. Appl. Phys. 94(5), 3121–3127 (2003). [CrossRef]

32.

J. Abell and T. D. Moustakas, “The role of dislocations as nonradiative recombination centers in InGaN quantum wells,” Appl. Phys. Lett. 92(9), 091901 (2008). [CrossRef]

33.

G. Chen, M. Craven, A. Kim, A. Munkholm, S. Watanabe, M. Camras, W. Götz, and F. Steranka, “Performance of high-power III-nitride light emitting diodes,” Phys. Status Solidi A 205(5), 1086–1092 (2008). [CrossRef]

OCIS Codes
(230.3670) Optical devices : Light-emitting diodes
(250.0250) Optoelectronics : Optoelectronics

ToC Category:
Light-Emitting Diodes

History
Original Manuscript: November 11, 2013
Revised Manuscript: December 27, 2013
Manuscript Accepted: February 25, 2014
Published: March 19, 2014

Citation
Chun-Ta Yu, Wei-Chih Lai, Cheng-Hsiung Yen, Hsu-Cheng Hsu, and Shoou-Jinn Chang, "Optoelectrical characteristics of green light-emitting diodes containing thick InGaN wells with digitally grown InN/GaN," Opt. Express 22, A633-A641 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-S3-A633


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