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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 1 — Jan. 14, 2013
  • pp: 1128–1136
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Dislocation density dependent electroabsorption in epitaxial lateral overgrown InGaN/GaN quantum structures

Emre Sari, Lee Woon Jang, Jong Hyeob Baek, In Hwan Lee, Xiao Wei Sun, and Hilmi Volkan Demir  »View Author Affiliations


Optics Express, Vol. 21, Issue 1, pp. 1128-1136 (2013)
http://dx.doi.org/10.1364/OE.21.001128


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Abstract

We study electroabsorption (EA) behavior of InGaN/GaN quantum structures grown using epitaxial lateral overgrowth (ELOG) in correlation with their dislocation density levels and in comparison to steady state and time-resolved photoluminescence measurements. The results reveal that ELOG structures with decreasing mask stripe widths exhibit stronger EA performance, with a maximum EA enhancement factor of 4.8 compared to the reference without ELOG. The analyses show that the EA performance follows similar trends with decreasing dislocation density as the essential parameters of the photoluminescence spectra (peak position, width and intensity) together with the photoluminescence lifetimes. While keeping the growth window widths constant, compared to photoluminescence behavior, however, EA surprisingly exhibits the largest performance variation, making EA the most sensitive to the mask stripe widths.

© 2013 OSA

1. Introduction

However, common to all non-native substrates of GaN, sapphire exhibits a large crystal lattice mismatch (about 14%), forming dislocations in the epitaxy as a result of the relaxation of the strain induced during the epitaxial growth. For the state-of-the-art bulk templates (those grown with the traditional nucleation layer approach, i.e., epi-growth directly on sapphire), e.g., in commercial LEDs, defect densities still remain in the range of 108 cm−2. The typical levels are, however, estimated to be in the 109 cm−2 range [3

3. C.-Y. Cho, J.-B. Lee, S.-J. Lee, S.-H. Han, T.-Y. Park, J. W. Kim, Y. C. Kim, and S.-J. Park, “Improvement of light output power of InGaN/GaN light-emitting diode by lateral epitaxial overgrowth using pyramidal-shaped SiO2.,” Opt. Express 18(2), 1462–1468 (2010). [CrossRef] [PubMed]

5

5. S. Nakamura, “The roles of structural imperfections in InGaN-based blue light-emitting diodes and laser diodes,” Science 281(5379), 956–961 (1998). [CrossRef] [PubMed]

]. Further reduction of the defect densities requires special techniques for the relaxation of strain and/or termination of defects formed during the growth [6

6. P. Gibart, “Metal organic vapour phase epitaxy of GaN and lateral overgrowth,” Rep. Prog. Phys. 67(5), 667–715 (2004). [CrossRef]

].

Epitaxial lateral overgrowth (ELOG), which is based on selective area growth, is one of the most powerful techniques for the reduction of threading dislocation densities, thus enabling substantial improvement in the crystal quality of GaN material system [5

5. S. Nakamura, “The roles of structural imperfections in InGaN-based blue light-emitting diodes and laser diodes,” Science 281(5379), 956–961 (1998). [CrossRef] [PubMed]

]. Under proper conditions, ELOG results in smooth surfaces with low defect densities by blocking propagation of the defects underneath the hard mask, usually defined by Si3N4 or SiO2 on a GaN template. This involves lateral growth over the mask, hence preventing the defects from propagating to the surface and leading to a surface with significantly fewer defects for the growth of subsequent layers [6

6. P. Gibart, “Metal organic vapour phase epitaxy of GaN and lateral overgrowth,” Rep. Prog. Phys. 67(5), 667–715 (2004). [CrossRef]

]. As investigated by several groups studying photoluminescence properties to date, ELOG has proven to be a successful method to improve GaN material quality as well as the performance of resulting optoelectronic devices including LEDs [4

4. C. Bayram, J. L. Pau, R. McClintock, and M. Razeghi, “Comprehensive study of blue and green multi-quantum-well light emitting diodes grown on conventional and lateral epitaxial overgrowth GaN,” Appl. Phys. B 95(2), 307–314 (2009). [CrossRef]

] and LDs [7

7. S. Nakamura, M. Senoh, S. Nagahama, N. Iwasa, T. Yamada, T. Matsushita, H. Kiyoku, Y. Sugimoto, T. Kozaki, H. Umemoto, M. Sano, and K. Chocho, “InGaN/GaN/AlGaN-based laser diodes with modulation-doped strained-layer superlattices grown on an epitaxially laterally overgrown GaN substrate,” Appl. Phys. Lett. 72(2), 211–213 (1998). [CrossRef]

] when grown on polar [8

8. A. Usui, H. Sunakawa, A. Sakai, and A. A. Yamaguchi, “Thick GaN epitaxial growth with low dislocation density by hydride vapor phase epitaxy,” Jpn. J. Appl. Phys. 36(Part 2, No. 7B), L899–L902 (1997). [CrossRef]

], semipolar [9

9. C. F. Johnston, M. A. Moram, M. J. Kappers, and C. J. Humphreys, “Defect reduction in (11-22) semipolar GaN grown on m-plane sapphire using ScN interlayers,” Appl. Phys. Lett. 94(16), 161109 (2009). [CrossRef]

] and nonpolar [10

10. B. M. Imer, F. Wu, S. P. DenBaars, and J. S. Speck, “Improved quality (11-20) a-plane GaN with sidewall lateral epitaxial overgrowth,” Appl. Phys. Lett. 88(6), 061908 (2006). [CrossRef]

] directions of their crystals. ELOG-LEDs with embedded micro mirror arrays have also been demonstrated to further improve the light extraction efficiency [11

11. C. Y. Huang, H. M. Ku, C. Z. Liao, and S. Chao, “MQWs InGaN/GaN LED with embedded micro-mirror array in the epitaxial-lateral-overgrowth gallium nitride for light extraction enhancement,” Opt. Express 18(10), 10674–10684 (2010). [CrossRef] [PubMed]

].

In terms of understanding the underpinning physical mechanisms, electroabsorption offers a unique means to explore and understand physics of semiconductor structures. This is especially the case for quantum-confined structures, which exhibit electroabsorption exceptionally stronger than their bulk counterparts through quantum-confined Stark effect (QCSE) [12

12. D. A. B. Miller, D. S. Chemla, T. C. Damen, A. C. Gossard, W. Wiegmann, T. H. Wood, and C. A. Burrus, “Electric field dependence of optical absorption near the bandgap of quantum well Structures,” Phys. Rev. B 32(2), 1043–1060 (1985). [CrossRef]

]. Electroabsorption modulators that utilize QCSE have found applications in telecommunications in the last few decades, e.g., in data coding [13

13. H. V. Demir, V. A. Sabnis, O. Fidaner, J. S. Harris Jr, D. A. B. Miller, and J.-F. Zheng, “Dual-diode quantum-well modulator for C-band wavelength conversion and broadcasting,” Opt. Express 12(2), 310–316 (2004). [CrossRef] [PubMed]

] and optical switching [14

14. H. V. Demir, V. A. Sabnis, O. Fidaner, J.-F. Zheng, J. S. Harris Jr, and D. A. B. Miller, “Multifunctional integrated photonic switches,” IEEE J. Sel. Top. Quantum Electron. 11(1), 86–96 (2005). [CrossRef]

]. Most of these studies involved InP/GaAs material system, and the operation wavelength of these devices has therefore been typically in the mid-infrared part of the electromagnetic spectrum. On the other hand, electroabsorption modulators based on III-Nitride quantum structures, which operate in the blue [15

15. E. Sari, S. Nizamoglu, T. Ozel, and H. V. Demir, “Blue quantum electroabsorption modulators based on reversed quantum confined Stark effect with blueshift,” Appl. Phys. Lett. 90(1), 011101 (2007). [CrossRef]

] and ultraviolet [16

16. I. Friel, C. Thomidis, and T. D. Moustakas, “Ultraviolet electroabsorption modulator based on AlGaN/GaN multiple quantum wells,” J. Appl. Phys. 97(12), 123515 (2005). [CrossRef]

] region of the electromagnetic spectrum, were also demonstrated. These find applications in optical clock injection directly into silicon chips [17

17. A. Bhatnagar, S. Latif, C. Debaes, and D. A. B. Miller, “Pump-probe measurements of CMOS detector rise time in the blue,” J. Lightwave Technol. 22(9), 2213–2217 (2004). [CrossRef]

] and none-of-sight communications [18

18. Z. Xu, G. Chen, F. Abou-Galala, and M. Leonardi, “Experimental performance evaluation of non-line-of-sight ultraviolet communication systems,” Proc. SPIE 6709, 67090Y (2007). [CrossRef]

]. However, electroabsorption in InGaN/GaN quantum structures grown on ELOG-GaN has not been investigated to date.

Here in this paper, we report electroabsorption performance of epitaxial lateral overgrown InGaN/GaN quantum structures, in comparison to their steady-state and time-resolved photoluminescence properties, and correlate our results with the dislocation density levels. In this study, we employ a set of four epi-structures, three of which are designed to contain systematically varying ELOG mask stripe widths while the last one is used as a reference sample without ELOG.

2. Epitaxial growth and device fabrication

Our epitaxial structures were grown using metal-organic chemical vapor deposition (MOCVD). After the growth of 5 µm thick u-GaN templates on single side polished sapphire substrates, we deposited and defined SiO2 stripe patterns all in (0-100) direction. The width of the SiO2 stripe masks is varied to be 4, 7 and 10 µm, whereas that of the unmasked window regions is kept constant at 4 µm for the three samples containing ELOG stripe patterns. No patterning was used for the fourth sample, which serves as the reference. We followed a standard single step ELOG procedure [5

5. S. Nakamura, “The roles of structural imperfections in InGaN-based blue light-emitting diodes and laser diodes,” Science 281(5379), 956–961 (1998). [CrossRef] [PubMed]

]. The lateral growth time was sufficiently long for each of our samples to completely coalesce in the middle-top part of the mask regions. After the coalescence, we changed the growth mode to vertical growth to obtain 2 µm thick Si doped n-type GaN layer (NSi ≈4 × 1018 cm−3) and InGaN/GaN multiple quantum well (MQW) structure with 5 pairs of well and barriers having thicknesses of 2.5 and 7.5 nm, respectively. After the growth of the MQW, we continued with Mg-doped 150 nm thick p-GaN layer (NMg ≈6 × 1017 cm−3) and completed the epi-samples.

We fabricated devices using these ELOG and reference epi-samples utilizing standard photolithography, mesa etching and metallization procedures. The fabrication and subsequent characterization of the devices were performed under the same conditions, all with identical settings and parameters. The mesa size of the resulting devices is 300 µm × 300 µm. These devices allowed us to apply external bias and extract photocurrent for electroabsorption study (in the case of reverse biasing).

3. Results and discussions

Following the MOCVD ELOG growth of our samples, we measured the dislocation densities through forming etch pits using wet etching and investigating scanning electron microscopy (SEM) images presented in Figs. 1(a)
Fig. 1 Representative parts of the analyzed scanning electron microscopy images of the top surface of our epi-structures after etch pit formation: (a) reference sample, and ELOG samples with (b) 4 µm, (c) 7 µm, and (d) 10 µm wide stripes.
1(d). Our analyses showed that the etch pit density for the reference sample was the highest and that of the ELOG sample with 4 µm wide stripes was the lowest, with the respective values of 3.25 × 108 and 0.88 × 108 cm−2. The etch pit densities of the other ELOG structures with 7 and 10 µm wide stripes were 1.84 × 108 and 1.58 × 108 cm−2, respectively.

In addition, we performed photoluminescence (PL) measurements using our setup containing a He-Cd laser at 325 nm, an optical microscope with a high magnifying power (100 × ) objective lens and a motorized stage, a monochromator, and a broadband photodetector. We carefully set the position and spot size (~2 μm) of the incoming laser beam properly such that all photons that contribute to the PL signal come from the low dislocation density region of the epitaxy. PL spectra corresponding to the Reference sample and the ELOG samples are given in Figs. 2(a)
Fig. 2 PL spectra of (a) reference sample, and ELOG samples with (b) 4 µm, (c) 7 µm and (d) 10 µm wide stripes.
2(d).

As a result of our PL measurements, we found that the PL peak emission wavelengths (λPL) were in the range of 466 ± 7 nm. This confirms that the levels of InN incorporated in the well regions of the MQW layers were similar to each other. Specifically, the structure with 4 µm wide stripes emit at the shortest wavelength, λPL, with the highest peak intensity, IPL. Moreover, the FWHM of the PL spectra, ΔλPL, was the lowest for the reference sample (18.47 nm), and very close to the sample with 4 µm stripes (18.53 nm). These results indicate that the Reference sample exhibits the weakest PL. (All important parameters of these PL spectra, which will later be discussed again to be compared against EA characterization results.)

Moreover, we performed time-resolved photoluminescence (TRPL) measurements for studying the carrier generation rate in the quantum structures. We used PicoQuant time-resolved photoluminescence setup comprising an InGaN-based laser diode operated at 375 nm in pulsed mode, with the monochromator center wavelength set at 466 nm in the photon collection side, for all of the samples. We fit the decay curves with three exponentials to obtain the minimum deviation from the actual data and considered the carrier recombination rates, Ri, as the reciprocal of the intensity averaged lifetimes, τi−1. We present the experimental TRPL decay curves of the four structures and the instrument response function (IRF), along with their numerical fits in Fig. 3
Fig. 3 Time-resolved photoluminescence decay profiles of our epitaxial lateral overgrowth structures and the reference sample along with their corresponding fits. The fastest decay profile corresponds to the reference sample due to its higher dislocation density, and thus higher nonradiative recombination rate. The instrument response function (IRF) is denoted by the black decay curve.
. In our fitting procedure, we deconvolve IRF from the actual decay data to extract photoluminescence lifetimes.

We further performed photocurrent measurements at different levels of reverse bias applied across our devices and recorded the field dependent change in the photocurrent, which corresponds to the electroabsorption of the samples under test. Our photocurrent setup consists of a broadband Xenon lamp, a monochromator, an optical chopper, a lock-in amplifier and a power supply; we carried out our photocurrent measurements in a probe station and coupled the incoming monochromatic light through the objective lens of the probe station microscope. The spot size of the light coupled to the devices is about 200 μm, which is smaller than our device mesa.

Here it is worth noting that, considering the geometries used and materials involved in the samples, mask patterns acting as optical scatterers have a very little effect on these EA measurements, because we are looking at the optical signal that is external field dependent. Moreover, since we use single side polished sapphire substrates, any such effect will be minimal due to light diffusion through the unpolished side. Due to the partial compensation of the polarization-induced electrostatic fields inside the well layers by the external electric field, we observed a strong blue shift of the absorption edge and thus, a decrease in the absorption level around the band edge, with increasing external bias. Such an electroabsorption behavior, called reversed quantum-confined Stark effect, has been observed previously [14

14. H. V. Demir, V. A. Sabnis, O. Fidaner, J.-F. Zheng, J. S. Harris Jr, and D. A. B. Miller, “Multifunctional integrated photonic switches,” IEEE J. Sel. Top. Quantum Electron. 11(1), 86–96 (2005). [CrossRef]

, 21

21. E. Sari, S. Nizamoglu, I.-H. Lee, J.-H. Baek, and H. V. Demir, “Electric field dependent radiative decay kinetics of polar InGaN/GaN quantum heterostructures at low fields,” Appl. Phys. Lett. 94(21), 211107 (2009). [CrossRef]

].

In our experimental measurements, we consistently observe that the lower dislocation density leads to stronger electroabsorption, although this dependence of electroabsorption on dislocation density may not be obvious for those who are more familiar with photoluminescence (e.g., LEDs). As an important remark, our results suggest that the electroabsorption performance of the best performing ELOG structure (4 µm stripe width) is about 3-fold better than its nearest competitor (7 µm stripe width). This performance difference of EA is significantly larger than the ratio of their corresponding PL intensities. Furthermore, this strong electroabsorption is 4.8-fold larger than the Reference sample without ELOG.

Compared to the PL intensity levels, this then suggests that, while keeping the growth window widths constant, EA exhibits larger sensitivity to the decreasing ELOG mask stripe widths, which reduces dislocation density. This observation therefore indicates surprisingly that EA results in the strongest dependence on the mask stripe widths.

We attribute the observed strong dependence of electroabsorption performance on the dislocation density to higher quality quantum well layers with more uniform thickness and more abrupt interfaces in lower dislocation density samples. Also, considering the fact that strain-induced piezoelectric polarization fields (and thus the total polarization-induced electrostatic fields) inside the well layers bend the conduction and valence bands of the low dislocation density samples more compared to others, they yield a narrower effective bandgap, which causes a red shift in the emission and absorption of the c-plane grown polar InGaN/GaN quantum structures. As a result, the 4 µm ELOG sample’s shortest emission wavelength can be explained by its lower amount of the residual strain [22

22. S.-M. Kim, H. S. Oh, J. H. Baek, K.-H. Lee, G. Y. Jung, J.-H. Song, H.-J. Kim, B.-J. Ahn, D. Yanqun, and J.-H. Song, “Effects of patterned sapphire substrates on piezoelectric field in blue-emitting InGaN multiple quantum wells,” IEEE Electron Device Lett. 31(8), 842–844 (2010). [CrossRef]

,23

23. S. J. Tu, J. K. Sheu, M. L. Lee, C. C. Yang, K. H. Chang, Y. H. Yeh, F. W. Huang, and W. C. Lai, “Enhanced output power of GaN-based LEDs with embedded AlGaN pyramidal shells,” Opt. Express 19(13), 12719–12726 (2011). [CrossRef] [PubMed]

], which is released at the coalescence sidewalls more compared to other samples [24

24. L. Y. Chen, H. H. Huang, C. H. Chang, Y. Y. Huang, Y. R. Wu, and J. J. Huang, “Investigation of the strain induced optical transition energy shift of the GaN nanorod light emitting diode arrays,” Opt. Express 19(S4Suppl 4), A900–A907 (2011). [CrossRef] [PubMed]

]. Since this sample has more stripes, there are more coalescence sidewalls available per unit area. Thus, as a result of the increased crystal quality and the reduced residual strain, the electroabsorption performance is the strongest in the 4 µm ELOG sample compared to the reference. With the decreased levels of dislocation density and residual strain, epitaxial lateral overgrowth therefore enables strong electroabsorption in InGaN/GaN multiple quantum wells.

3. Conclusions

Acknowledgments

This work is supported by EC-FP7 N4E NoE and TUBITAK EEEAG 110E010 and 110E217, and in part by NRF-RF-2009-09 and NRF-CRP-6-2010-02. This work is also partially supported by South Korea NRF 2010-616-D00056. H.V.D. acknowledges support from ESF-EURYI and TUBA-GEBIP; and E.S. from TUBITAK BIDEB 2211 and 2214.

References and links

1.

H. Zhao, G. Liu, J. Zhang, J. D. Poplawsky, V. Dierolf, and N. Tansu, “Approaches for high internal quantum efficiency green InGaN light-emitting diodes with large overlap quantum wells,” Opt. Express 19(S4Suppl 4), A991–A1007 (2011). [CrossRef] [PubMed]

2.

S. P. Denbaars, “Gallium-nitride-based materials for blue to ultraviolet optoelectronics devices,” Proc. IEEE 85(11), 1740–1749 (1997). [CrossRef]

3.

C.-Y. Cho, J.-B. Lee, S.-J. Lee, S.-H. Han, T.-Y. Park, J. W. Kim, Y. C. Kim, and S.-J. Park, “Improvement of light output power of InGaN/GaN light-emitting diode by lateral epitaxial overgrowth using pyramidal-shaped SiO2.,” Opt. Express 18(2), 1462–1468 (2010). [CrossRef] [PubMed]

4.

C. Bayram, J. L. Pau, R. McClintock, and M. Razeghi, “Comprehensive study of blue and green multi-quantum-well light emitting diodes grown on conventional and lateral epitaxial overgrowth GaN,” Appl. Phys. B 95(2), 307–314 (2009). [CrossRef]

5.

S. Nakamura, “The roles of structural imperfections in InGaN-based blue light-emitting diodes and laser diodes,” Science 281(5379), 956–961 (1998). [CrossRef] [PubMed]

6.

P. Gibart, “Metal organic vapour phase epitaxy of GaN and lateral overgrowth,” Rep. Prog. Phys. 67(5), 667–715 (2004). [CrossRef]

7.

S. Nakamura, M. Senoh, S. Nagahama, N. Iwasa, T. Yamada, T. Matsushita, H. Kiyoku, Y. Sugimoto, T. Kozaki, H. Umemoto, M. Sano, and K. Chocho, “InGaN/GaN/AlGaN-based laser diodes with modulation-doped strained-layer superlattices grown on an epitaxially laterally overgrown GaN substrate,” Appl. Phys. Lett. 72(2), 211–213 (1998). [CrossRef]

8.

A. Usui, H. Sunakawa, A. Sakai, and A. A. Yamaguchi, “Thick GaN epitaxial growth with low dislocation density by hydride vapor phase epitaxy,” Jpn. J. Appl. Phys. 36(Part 2, No. 7B), L899–L902 (1997). [CrossRef]

9.

C. F. Johnston, M. A. Moram, M. J. Kappers, and C. J. Humphreys, “Defect reduction in (11-22) semipolar GaN grown on m-plane sapphire using ScN interlayers,” Appl. Phys. Lett. 94(16), 161109 (2009). [CrossRef]

10.

B. M. Imer, F. Wu, S. P. DenBaars, and J. S. Speck, “Improved quality (11-20) a-plane GaN with sidewall lateral epitaxial overgrowth,” Appl. Phys. Lett. 88(6), 061908 (2006). [CrossRef]

11.

C. Y. Huang, H. M. Ku, C. Z. Liao, and S. Chao, “MQWs InGaN/GaN LED with embedded micro-mirror array in the epitaxial-lateral-overgrowth gallium nitride for light extraction enhancement,” Opt. Express 18(10), 10674–10684 (2010). [CrossRef] [PubMed]

12.

D. A. B. Miller, D. S. Chemla, T. C. Damen, A. C. Gossard, W. Wiegmann, T. H. Wood, and C. A. Burrus, “Electric field dependence of optical absorption near the bandgap of quantum well Structures,” Phys. Rev. B 32(2), 1043–1060 (1985). [CrossRef]

13.

H. V. Demir, V. A. Sabnis, O. Fidaner, J. S. Harris Jr, D. A. B. Miller, and J.-F. Zheng, “Dual-diode quantum-well modulator for C-band wavelength conversion and broadcasting,” Opt. Express 12(2), 310–316 (2004). [CrossRef] [PubMed]

14.

H. V. Demir, V. A. Sabnis, O. Fidaner, J.-F. Zheng, J. S. Harris Jr, and D. A. B. Miller, “Multifunctional integrated photonic switches,” IEEE J. Sel. Top. Quantum Electron. 11(1), 86–96 (2005). [CrossRef]

15.

E. Sari, S. Nizamoglu, T. Ozel, and H. V. Demir, “Blue quantum electroabsorption modulators based on reversed quantum confined Stark effect with blueshift,” Appl. Phys. Lett. 90(1), 011101 (2007). [CrossRef]

16.

I. Friel, C. Thomidis, and T. D. Moustakas, “Ultraviolet electroabsorption modulator based on AlGaN/GaN multiple quantum wells,” J. Appl. Phys. 97(12), 123515 (2005). [CrossRef]

17.

A. Bhatnagar, S. Latif, C. Debaes, and D. A. B. Miller, “Pump-probe measurements of CMOS detector rise time in the blue,” J. Lightwave Technol. 22(9), 2213–2217 (2004). [CrossRef]

18.

Z. Xu, G. Chen, F. Abou-Galala, and M. Leonardi, “Experimental performance evaluation of non-line-of-sight ultraviolet communication systems,” Proc. SPIE 6709, 67090Y (2007). [CrossRef]

19.

I.-L. Lu, Y.-R. Wu, and J. Singh, “A study of the role of dislocation density, indium composition on the radiative efficiency in InGaN/GaN polar and nonpolar light-emitting diodes using drift-diffusion coupled with a Monte Carlo method,” J. Appl. Phys. 108(12), 124508 (2010). [CrossRef]

20.

M. F. Schubert, S. Chhajed, J. K. Kim, E. F. Schubert, D. D. Koleske, M. H. Crawford, S. R. Lee, A. J. Fischer, G. Thaler, and M. A. Banas, “Effect of dislocation density on efficiency droop in GaInN/GaN light-emitting diodes,” Appl. Phys. Lett. 91(23), 231114 (2007). [CrossRef]

21.

E. Sari, S. Nizamoglu, I.-H. Lee, J.-H. Baek, and H. V. Demir, “Electric field dependent radiative decay kinetics of polar InGaN/GaN quantum heterostructures at low fields,” Appl. Phys. Lett. 94(21), 211107 (2009). [CrossRef]

22.

S.-M. Kim, H. S. Oh, J. H. Baek, K.-H. Lee, G. Y. Jung, J.-H. Song, H.-J. Kim, B.-J. Ahn, D. Yanqun, and J.-H. Song, “Effects of patterned sapphire substrates on piezoelectric field in blue-emitting InGaN multiple quantum wells,” IEEE Electron Device Lett. 31(8), 842–844 (2010). [CrossRef]

23.

S. J. Tu, J. K. Sheu, M. L. Lee, C. C. Yang, K. H. Chang, Y. H. Yeh, F. W. Huang, and W. C. Lai, “Enhanced output power of GaN-based LEDs with embedded AlGaN pyramidal shells,” Opt. Express 19(13), 12719–12726 (2011). [CrossRef] [PubMed]

24.

L. Y. Chen, H. H. Huang, C. H. Chang, Y. Y. Huang, Y. R. Wu, and J. J. Huang, “Investigation of the strain induced optical transition energy shift of the GaN nanorod light emitting diode arrays,” Opt. Express 19(S4Suppl 4), A900–A907 (2011). [CrossRef] [PubMed]

OCIS Codes
(160.4760) Materials : Optical properties
(160.6000) Materials : Semiconductor materials
(230.0250) Optical devices : Optoelectronics

ToC Category:
Materials

History
Original Manuscript: September 18, 2012
Revised Manuscript: November 15, 2012
Manuscript Accepted: December 13, 2012
Published: January 10, 2013

Citation
Emre Sari, Lee Woon Jang, Jong Hyeob Baek, In Hwan Lee, Xiao Wei Sun, and Hilmi Volkan Demir, "Dislocation density dependent electroabsorption in epitaxial lateral overgrown InGaN/GaN quantum structures," Opt. Express 21, 1128-1136 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-1-1128


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References

  1. H. Zhao, G. Liu, J. Zhang, J. D. Poplawsky, V. Dierolf, and N. Tansu, “Approaches for high internal quantum efficiency green InGaN light-emitting diodes with large overlap quantum wells,” Opt. Express19(S4Suppl 4), A991–A1007 (2011). [CrossRef] [PubMed]
  2. S. P. Denbaars, “Gallium-nitride-based materials for blue to ultraviolet optoelectronics devices,” Proc. IEEE85(11), 1740–1749 (1997). [CrossRef]
  3. C.-Y. Cho, J.-B. Lee, S.-J. Lee, S.-H. Han, T.-Y. Park, J. W. Kim, Y. C. Kim, and S.-J. Park, “Improvement of light output power of InGaN/GaN light-emitting diode by lateral epitaxial overgrowth using pyramidal-shaped SiO2.,” Opt. Express18(2), 1462–1468 (2010). [CrossRef] [PubMed]
  4. C. Bayram, J. L. Pau, R. McClintock, and M. Razeghi, “Comprehensive study of blue and green multi-quantum-well light emitting diodes grown on conventional and lateral epitaxial overgrowth GaN,” Appl. Phys. B95(2), 307–314 (2009). [CrossRef]
  5. S. Nakamura, “The roles of structural imperfections in InGaN-based blue light-emitting diodes and laser diodes,” Science281(5379), 956–961 (1998). [CrossRef] [PubMed]
  6. P. Gibart, “Metal organic vapour phase epitaxy of GaN and lateral overgrowth,” Rep. Prog. Phys.67(5), 667–715 (2004). [CrossRef]
  7. S. Nakamura, M. Senoh, S. Nagahama, N. Iwasa, T. Yamada, T. Matsushita, H. Kiyoku, Y. Sugimoto, T. Kozaki, H. Umemoto, M. Sano, and K. Chocho, “InGaN/GaN/AlGaN-based laser diodes with modulation-doped strained-layer superlattices grown on an epitaxially laterally overgrown GaN substrate,” Appl. Phys. Lett.72(2), 211–213 (1998). [CrossRef]
  8. A. Usui, H. Sunakawa, A. Sakai, and A. A. Yamaguchi, “Thick GaN epitaxial growth with low dislocation density by hydride vapor phase epitaxy,” Jpn. J. Appl. Phys.36(Part 2, No. 7B), L899–L902 (1997). [CrossRef]
  9. C. F. Johnston, M. A. Moram, M. J. Kappers, and C. J. Humphreys, “Defect reduction in (11-22) semipolar GaN grown on m-plane sapphire using ScN interlayers,” Appl. Phys. Lett.94(16), 161109 (2009). [CrossRef]
  10. B. M. Imer, F. Wu, S. P. DenBaars, and J. S. Speck, “Improved quality (11-20) a-plane GaN with sidewall lateral epitaxial overgrowth,” Appl. Phys. Lett.88(6), 061908 (2006). [CrossRef]
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