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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 12 — Jun. 6, 2011
  • pp: 11873–11879
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Electroluminescence of ZnO nanocrystal in sputtered ZnO-SiO2 nanocomposite light-emitting devices

Jiun-Ting Chen, Wei-Chih Lai, Chi-Heng Chen, Ya-Yu Yang, Jinn-Kong Sheu, and Li-Wen Lai  »View Author Affiliations


Optics Express, Vol. 19, Issue 12, pp. 11873-11879 (2011)
http://dx.doi.org/10.1364/OE.19.011873


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Abstract

We have demonstrated the electroluminescence (EL) of Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN n-i-p heterostructure light-emitting devices (LEDs). ZnO nano-clusters with sizes distributing from 2 to 7nm were found inside the co-sputtered i-ZnO-SiO2 nanocomposite layer under the observation of high-resolution transparent electron microscope. A clear UV EL at 376 nm from i-ZnO-SiO2 nanocomposite in these p-i-n heterostructure LEDs was observed under the forward current of 9 mA. The EL emission peak at 376 and 427nm of the Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN n-i-p heterostructure LEDs were attributed to the radiative recombination from the ZnO clusters and the Mg acceptor levels in the p-GaN layer, respectively.

© 2011 OSA

1. Introduction

ZnO has a direct bandgap of 3.37 eV at room temperature, a high free exciton-binding energy of 60 meV, and the likelihood of efficient excitonic optical transitions at elevated temperatures [1

1. D. C. Look, “Doping and defects in ZnO, in ZnO bulk,” in Thin Films and Nanostructures, C. Jagadish and S. J. Pearton, (Elsevier, Oxford, 2006).

,2

2. D. M. Bagnall, Y. F. Chen, Z. Zhu, T. Yao, M. Y. Shen, and T. Goto, “High temperature excitonic stimulated emission from ZnO epitaxial layers,” Appl. Phys. Lett. 73(8), 1038–1040 (1998). [CrossRef]

]. ZnO also offers several advantages: simple processing due to its compatibility with wet chemical etching, relatively low material costs, and long-term stability, among others. The natural n-type characteristic of ZnO from oxygen vacancies and Zn interstitials [3

3. R. Hong, H. Qi, J. Huang, H. He, Z. Fan, and J. Shao, “Influence of oxygen partial pressure on the structure and photoluminescence of direct current reactive magnetron sputtering ZnO thin films,” Thin Solid Films 473(1), 58–62 (2005). [CrossRef]

] is a great barrier to getting p-type ZnO. However, several reports have demonstrated advanced ZnO-based light emitting devices (LEDs) [4

4. A. Tsukazaki, A. Ohtomo, T. Onuma, M. Ohtani, T. Makino, M. Sumiya, K. Ohtani, S. F. Chichibu, S. Fuke, Y. Segawa, H. Ohno, H. Koinuma, and M. Kawasaki, “Repeated temperature modulation epitaxy for p-type doping and light- emitting diode based on ZnO,” Nat. Mater. 4(1), 42–46 (2005). [CrossRef]

,5

5. S. Kim, F. Lugo, S. J. Pearton, D. P. Norton, Y.-L. Wang, and F. Ren, “Phosphorus doped ZnO light emitting diodes fabricated via pulsed laser deposition,” Appl. Phys. Lett. 92(11), 112108-112110(2008). [CrossRef]

], causing ZnO to gain more attention for its applications in short-wavelength LEDs and laser diodes suitable for high-temperature operations. Up to now, although the homojunction or p-i-n structure of ZnO diodes are still being reported [4

4. A. Tsukazaki, A. Ohtomo, T. Onuma, M. Ohtani, T. Makino, M. Sumiya, K. Ohtani, S. F. Chichibu, S. Fuke, Y. Segawa, H. Ohno, H. Koinuma, and M. Kawasaki, “Repeated temperature modulation epitaxy for p-type doping and light- emitting diode based on ZnO,” Nat. Mater. 4(1), 42–46 (2005). [CrossRef]

,5

5. S. Kim, F. Lugo, S. J. Pearton, D. P. Norton, Y.-L. Wang, and F. Ren, “Phosphorus doped ZnO light emitting diodes fabricated via pulsed laser deposition,” Appl. Phys. Lett. 92(11), 112108-112110(2008). [CrossRef]

], difficulties in realizing reliable p-type ZnO [6

6. S. B. Zhang, S. H. Wei, and A. Zunger, “Intrinsic n-type versus p-type doping asymmetry and the defect physics of ZnO,” Phys. Rev. B 63(7), 075205–075205 (2001). [CrossRef]

,7

7. D. C. Look, D. C. Reynolds, C. W. Litton, R. L. Jones, D. B. Eason, and G. Cantwell, “Characterization of homoepitaxial p-type ZnO grown by molecular beam epitaxy,” Appl. Phys. Lett. 81(10), 1830–1832 (2002). [CrossRef]

] have driven most ZnO-based LEDs to develop on heterostructures by growing n-ZnO on p-type semiconductors, such as GaN, Si, AlGaN, and p-SrCu2O2 [8

8. J. Y. Lee, J. H. Lee, H. S. Kim, C. H. Lee, H. S. Ahn, H. K. Cho, Y. Y. Kim, B. H. Kong, and H. S. Lee, “A study on the origin of emission of the annealed n-ZnO/p-GaN heterostructure LED,” Thin Solid Films 517(17), 5157–5160 (2009). [CrossRef]

11

11. H. Ohta, K. Kawamura, M. Orita, M. Hirano, N. Sarukura, and H. Hosono, “Current injection emission from a transparent p –n junction composed of p-SrCu2O2 /n-ZnO,” Appl. Phys. Lett. 77(4), 475–477 (2000). [CrossRef]

]. In general, the p-type GaN (p-GaN) is a good choice for the ZnO heterostructure LEDs because of the wurtzite structure of ZnO [12

12. Y. I. Alivov, J. E. V. Nostrand, D. C. Look, M. V. Chukichev, and B. M. Ataev, “Observation of 430 nm electroluminescence from ZnO/GaN heterojunction light-emitting diodes,” Appl. Phys. Lett. 83(14), 2943–2945 (2003). [CrossRef]

]. However, not just the ultraviolet emission alone, several emissions including blue, orange and green bands because the presence of the zinc interstitials, oxygen vacancies or oxygen interstitials, are also observed from these homo or heterojunction devices [13

13. K. Vanheusden, C. H. Seager, W. L. Warren, D. R. Tallant, and J. A. Voigt, “Correlation between photoluminescence and oxygen vacancies in ZnO phosphors,” Appl. Phys. Lett. 68(3), 403–405 (1996). [CrossRef]

,14

14. X. L. Wu, G. G. Siu, C. L. Fu, and H. C. Ong, “Photoluminescence and cathodoluminescence studies of stoichiometric and oxygen-deficient ZnO films,” Appl. Phys. Lett. 78(16), 2285–2287 (2001). [CrossRef]

]. This phenomenon is ascribed to the radiative recombination path involving the deep level states in the ZnO thin film device. Therefore, pure strongly ultraviolet emission compared to other emissions from ZnO light-emitting diodes is hard to achieve.

Besides, for improving the emission efficiency of the ZnO based LEDs, ZnO nanoparticles are of great interest because of their three-dimensional quantum confinement, which strongly enhances the excitation radiative recombination. Recently, nanoscale or submicron sized ZnO materials have also been synthesized through various methods [15

15. L. Mädler, W. J. Stark, and S. E. Pratsinis, “Rapid synthesis of stable ZnO quantum dots,” J. Appl. Phys. 92(11), 6537–6540 (2002). [CrossRef]

23

23. M. K. Wu, Y. T. Shih, M. J. Chen, J. R. Yang, and M. Shiojiri, “ZnO quantum dots embedded in a SiO2 nanoparticle layer grown by atomic layer deposition,” P hys,” Status Solidi RRL 3(2-3), 88–90 (2009). [CrossRef]

], such as sol–gel coating, sputtering technique, atomic layer deposition etc. For instance, Ma et al. [24

24. J. G. Ma, Y. C. Liu, C. S. Xu, Y. X. Liu, C. L. Shao, H. Y. Xu, J. Y. Zhang, Y. M. Lu, D. Z. Shen, and X. W. Fan, “Preparation and characterization of ZnO particles embedded in SiO2 matrix by reactive magnetron sputtering,” J. Appl. Phys. 97(10), 103509 (2005). [CrossRef]

] have successfully prepared ZnO nanoparticles by reactive magnetron sputtering and diffusion furnace method. Chen et al. [25

25. M. J. Chen, Y. T. Shih, M. K. Wu, H. C. Chen, H. L. Tsai, W. C. Li, J. R. Yang, H. Kuan, and M. Shiojiri, “Structure and Ultraviolet Electroluminescence of n-ZnO/SiO2-ZnO Nanocomposite/p-GaN Heterostructure Light-Emitting Diodes,” IEEE Trans. Electron. Dev. 57(9), 2195–2202 (2010). [CrossRef]

] and Shih et al. [26

26. Y. T. Shih, M. K. Wu, W. C. Li, H. Kuan, J. R. Yang, M. Shiojiri, and M. J. Chen, “Amplified spontaneous emission from ZnO in n-ZnO/ZnO nanodots–SiO2 composite/p-AlGaN heterojunction light-emitting diodes,” Nanotechnology 20(16), 1–8 (2009). [CrossRef]

] have reported that the ZnO was deposited in the small voids between SiO2 nanoparticles using atomic layer deposition (ALD) and spin coating methods. In this study, a simple and efficient co-sputtering method was proposed to fabricate ZnO nanoclusters in silica-based nanocomposites. ZnO-SiO2 nanocomposite and ZnO films were deposited on p-GaN as the active layer of the ultraviolet heterostructure ZnO-based LEDs. Furthermore, the optical and electrical characteristics of the fabricated heterostructure ZnO-based LEDs with ZnO-SiO2 nanocomposite and ZnO active layer are discussed as well.

2. Experiments

The ZnO-SiO2 nanocomposite and ZnO thin films were deposited on p-GaN substrate by RF magnetron and DC co-sputtering system. SiO2 and ZnO disks on the separated RF and DC sputtering guns were used as sputtering targets for the Si, Zn, and O elements, respectively. The sputtering chamber was pumped to a high vacuum of 5x10−6 torr using a turbo molecular pump. Afterwards, Ar gas was introduced into the sputtering chamber through a set of mass flow controllers using the flow rate of 10 sccm (standard cubic centimeters per minute). The working pressure was set at 5 mtorr, and all the samples were deposited at room temperature during the sputtering process. To form the 100 nm-thick ZnO-SiO2 nanocomposite films, SiO2 and ZnO were sputtered and deposited simultaneously on the p-GaN substrate. The RF power of the SiO2 target and DC power of the ZnO target were 125 and 75 W, respectively. A 100 nm-thick ZnO film was deposited on p-GaN with 75 W DC power as an active layer of the ZnO-based heterostructure LEDs. On the other hand, a 120 nm-thick Ga:ZnO was deposited on the ZnO-SiO2 nanocomposite, ZnO, and a p-GaN layer on the n-type layer of LEDs for comparison. Photolithography and buffer oxide etching solution were subsequently used to partially etch out the Ga:ZnO/ZnO-SiO2 nanocomposite, Ga:ZnO/ZnO, and Ga:ZnO until the p-GaN layer was exposed. Ni/Au (50 nm/200 nm) was deposited on p-GaN by evaporation to form ohmic contact with the p-electrode of LEDs. On the other hand, Cr/Au (50 nm/200 nm) was deposited on Ga:ZnO by evaporation to form ohmic contact with the n-electrode of LEDs. The microstructure of ZnO-SiO2 nanocomposite was examined using high-resolution transmission electron microscopy (HRTEM). As shown in Fig. 1
Fig. 1 Schematics of three structures (a) LED I (Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN LEDs), (b) LED II (Ga:ZnO/ZnO/p-GaN LEDs), and (c) LED III (Ga:ZnO/p-GaN LEDs).
, the size of all fabricated Ga:ZnO/ZnO-SiO2 nanocomposite/p-GaN (i.e., LED I), Ga:ZnO/ZnO/p-GaN (i.e., LED II), and Ga:ZnO/p-GaN (i.e., LED III) LEDs was kept at 300 x 300 μm2. An HP 4156 semiconductor parameter analyzer was then used to measure the current-voltage (I-V) characteristics of all fabricated LEDs. Electroluminescence (EL) spectra of all fabricated LEDs were also measured at room temperature.

3. Results and discussions

Figure 2
Fig. 2 I–V characteristics of LED I (Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN), LED II(Ga:ZnO /ZnO/p-GaN), and LED III (Ga:ZnO/p-GaN).
indicates the I-V curves of the fabricated LEDs I, II, and III. All samples exhibited a rectifying, diode-like behavior. Results revealed that the forward turn-on voltages of LED I, II, and III were 4.16, 3.70, and 3.14 V (at 50μA), respectively. On the other hand, the reverse breakdown voltages of LEDs I, II, and III were −13.6, −10.0, and −4.1 V (at −50μA), respectively. The Ga:ZnO/p-GaN heterojunction LEDs showed that the lowest turn-on voltage compared to the Ga:ZnO/ZnO/p-GaN and Ga:ZnO/ZnO-SiO2 nanocomposite/p-GaN p-i-n heterojunction LEDs. This phenomenon may due to the high resistance of the i-ZnO and i-ZnO-SiO2 nanocomposite layer increased the turn-on voltage of the p-i-n heterojunction LEDs. Meanwhile, the ZnSiOx compound might be formed in the ZnO and SiO2 of the co-sputtered ZnO-SiO2nanocomposite layer. The ZnSiOx compound in the ZnO-SiO2 nanocomposite layer might result in higher resistivity than in the i-ZnO layer, causing the Ga:ZnO/ZnO-SiO2 nanocomposite/p-GaN p-i-n heterojunction LEDs to have the highest turn-on voltage.

Figure 4
Fig. 4 EL spectra for LED I (Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN LEDs) at room temperature for various forward drive currents. The inset displays the L-I characteristics of the Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN LEDs.
displays the room temperature EL spectra of the Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN LEDs for five different injection currents. The double EL peak emission of LED I was observed for all the driving currents. The EL emission of LED I with wavelengths of 376 and 427 nm was found at 1 mA driving current. However, the intensity of the 376 nm emission at 1 mA was much less than for the 427 nm emission. The short wavelength EL emission of 376 nm could be from the ZnO clusters inside the co-sputtered i-ZnO-SiO2 nanocomposite layer. Both the 376 and 427 nm emission intensities of LED I increased with higher driving current. However, the intensity of the 376 nm emission of LED I was greater than that of the 427 nm emission when the driving current was larger than 7 mA. Under low driving current, such as 1 mA, the main EL emission peak at 427 nm of LED I could be attributed to the emission from the Mg acceptor levels in the p-GaN layer [8

8. J. Y. Lee, J. H. Lee, H. S. Kim, C. H. Lee, H. S. Ahn, H. K. Cho, Y. Y. Kim, B. H. Kong, and H. S. Lee, “A study on the origin of emission of the annealed n-ZnO/p-GaN heterostructure LED,” Thin Solid Films 517(17), 5157–5160 (2009). [CrossRef]

]. The EL main peak emissions of LED I turned from 427 to 376 nm with the high driving current, which could be attributed to the strong electron-hole recombination in the cluster size of the ZnO in i-ZnO-SiO2 nanocomposite layer under high injection current.

The inset presents the light output-current (L-I) characteristics of the Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN LEDs, which were obtained from a direct measurement of the peak emission intensity at 376 nm. As shown in a log-log scale, the L-I results can be fitted with the power law L~Im. The power exponent m is ~1. The obtained linear value of m is the Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN LEDs, and this result reveals the high efficiency of the carrier recombination that occurred in the Ga:ZnO/i-ZnO-SiO2 nanocomposite/p-GaN LEDs [27

27. I. Martil, E. Redondo, and A. Ojeda, “Influence of defects on the electrical and optical characteristics of blue light-emitting diodes on III-V nitrides,” J. Appl. Phys. 81(5), 2442–2444 (2007). [CrossRef]

]. Meanwhile, the structure of ZnO nanodots embedded in the amorphous SiOx matrix provided a larger energy barrier (ZnSiOx or SiOx), which improved the carrier confinement phenomenon in the i-ZnO-SiO2 nanocomposite layer.

From the EL emission results, the ultraviolet emission occurred from the ZnO clusters embedded in the ZnO-SiO2 nanocomposite can be realized. To understand clearly whether ZnO nanoclusters were in the i-ZnO-SiO2 nanocomposite layer, an HRTEM was used on the ZnO and SiO2 that co-sputtered the i-ZnO-SiO2 nanocomposite layer, as shown in Fig. 5
Fig. 5 HRTEM images of the sputtered ZnO-SiO2 nanocomposite layer. The inset of (b) displays TEM electron diffraction pattern of the ZnO nanocluster in ZnO-SiO2 nanocomposite layer
. A nanocrystallized material was found inside the i-ZnO-SiO2 nanocomposite layer in the HRTEM picture, as shown in Fig. 5 as well. The present study shows that the regular atom spacing of the nanocrystallized material was 0.248 nm, which should be correlated with the spacing of the (101) ZnO. Moreover, the sizes of the ZnO nanoclusters were distributed from 2 to 7 nm. Under low current injection, the injected carriers in the i-ZnO-SiO2 nanocomposite layer recombined in the ZnO nanocluster and came out the wide EL emission spectra in wavelength range of 360 to 400nm. However, under high current injection the injected carriers in the i-ZnO-SiO2 nanocomposite layer recombined efficiently in the high quantum confined ZnO nanoclusters and turned out the strong and sharp EL emission spectra with a peak wavelength of 376 nm.

4. Conclusion

Acknowledgments

The authors would like to acknowledge the financial support of the National Science Council for the research Grant Nos. NSC 97-2221-E-006-242-MY3. The present work was also supported in part by the Center for Frontier Materials and Micro/Nano Science and Technology and by the Advanced Optoelectronic Technology Center of the National Cheng Kung University under the projects supervised by the Ministry of Education.

References and links

1.

D. C. Look, “Doping and defects in ZnO, in ZnO bulk,” in Thin Films and Nanostructures, C. Jagadish and S. J. Pearton, (Elsevier, Oxford, 2006).

2.

D. M. Bagnall, Y. F. Chen, Z. Zhu, T. Yao, M. Y. Shen, and T. Goto, “High temperature excitonic stimulated emission from ZnO epitaxial layers,” Appl. Phys. Lett. 73(8), 1038–1040 (1998). [CrossRef]

3.

R. Hong, H. Qi, J. Huang, H. He, Z. Fan, and J. Shao, “Influence of oxygen partial pressure on the structure and photoluminescence of direct current reactive magnetron sputtering ZnO thin films,” Thin Solid Films 473(1), 58–62 (2005). [CrossRef]

4.

A. Tsukazaki, A. Ohtomo, T. Onuma, M. Ohtani, T. Makino, M. Sumiya, K. Ohtani, S. F. Chichibu, S. Fuke, Y. Segawa, H. Ohno, H. Koinuma, and M. Kawasaki, “Repeated temperature modulation epitaxy for p-type doping and light- emitting diode based on ZnO,” Nat. Mater. 4(1), 42–46 (2005). [CrossRef]

5.

S. Kim, F. Lugo, S. J. Pearton, D. P. Norton, Y.-L. Wang, and F. Ren, “Phosphorus doped ZnO light emitting diodes fabricated via pulsed laser deposition,” Appl. Phys. Lett. 92(11), 112108-112110(2008). [CrossRef]

6.

S. B. Zhang, S. H. Wei, and A. Zunger, “Intrinsic n-type versus p-type doping asymmetry and the defect physics of ZnO,” Phys. Rev. B 63(7), 075205–075205 (2001). [CrossRef]

7.

D. C. Look, D. C. Reynolds, C. W. Litton, R. L. Jones, D. B. Eason, and G. Cantwell, “Characterization of homoepitaxial p-type ZnO grown by molecular beam epitaxy,” Appl. Phys. Lett. 81(10), 1830–1832 (2002). [CrossRef]

8.

J. Y. Lee, J. H. Lee, H. S. Kim, C. H. Lee, H. S. Ahn, H. K. Cho, Y. Y. Kim, B. H. Kong, and H. S. Lee, “A study on the origin of emission of the annealed n-ZnO/p-GaN heterostructure LED,” Thin Solid Films 517(17), 5157–5160 (2009). [CrossRef]

9.

J. D. Ye, S. L. Gu, S. M. Zhu, W. Liu, S. M. Liu, R. Zhang, Y. Shi, and Y. D. Zheng, “Electroluminescent and transport mechanisms of n-ZnO/p-Si heterojunctions,” Appl. Phys. Lett. 88(18), 182112-182114(2006). [CrossRef]

10.

Y. I. Alivov, E. V. Kalinina, A. E. Cherenkov, D. C. Look, B. M. Ataev, A. K. Omaev, M. V. Chukichev, and D. M. Bagnall, “Fabrication and characterization of n-ZnO/p-AlGaN heterojunction light-emitting diodes on 6HSiC substrates,” Appl. Phys. Lett. 83(23), 4719–4721 (2003). [CrossRef]

11.

H. Ohta, K. Kawamura, M. Orita, M. Hirano, N. Sarukura, and H. Hosono, “Current injection emission from a transparent p –n junction composed of p-SrCu2O2 /n-ZnO,” Appl. Phys. Lett. 77(4), 475–477 (2000). [CrossRef]

12.

Y. I. Alivov, J. E. V. Nostrand, D. C. Look, M. V. Chukichev, and B. M. Ataev, “Observation of 430 nm electroluminescence from ZnO/GaN heterojunction light-emitting diodes,” Appl. Phys. Lett. 83(14), 2943–2945 (2003). [CrossRef]

13.

K. Vanheusden, C. H. Seager, W. L. Warren, D. R. Tallant, and J. A. Voigt, “Correlation between photoluminescence and oxygen vacancies in ZnO phosphors,” Appl. Phys. Lett. 68(3), 403–405 (1996). [CrossRef]

14.

X. L. Wu, G. G. Siu, C. L. Fu, and H. C. Ong, “Photoluminescence and cathodoluminescence studies of stoichiometric and oxygen-deficient ZnO films,” Appl. Phys. Lett. 78(16), 2285–2287 (2001). [CrossRef]

15.

L. Mädler, W. J. Stark, and S. E. Pratsinis, “Rapid synthesis of stable ZnO quantum dots,” J. Appl. Phys. 92(11), 6537–6540 (2002). [CrossRef]

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Y. Dai, Y. Zhang, Q. K. Li, and C. W. Nan, “Synthesis and optical properties of tetrapod-like zinc oxide nanorods,” Chem. Phys. Lett. 358(1-2), 83–86 (2002). [CrossRef]

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V. A. L. Roy, A. B. Djurišić, W. K. Chan, J. Gao, H. F. Lui, and C. Surya, “Luminescent and structural properties of ZnO nanorods prepared under different conditions,” Appl. Phys. Lett. 83(1), 141–143 (2003). [CrossRef]

21.

V. Musat, E. Fortunato, S. Petrescu, and A. M. Botelho do Rego, “ZnO/SiO2 nanocomposite thin films by sol–gel method,” Phys. Status Solidi., A Appl. Mater. Sci. 205(8), 2075–2079 (2008). [CrossRef]

22.

G. Kiliani, R. Schneider, D. Litvinov, D. Gerthsen, M. Fonin, U. Rudiger, A. Leitenstorfer, and R. Bratschitsch, “Ultraviolet photoluminescence of ZnO quantum dots sputtered at room-temperature,” Opt. Express 19(2), 1641–1647 (2011). [CrossRef] [PubMed]

23.

M. K. Wu, Y. T. Shih, M. J. Chen, J. R. Yang, and M. Shiojiri, “ZnO quantum dots embedded in a SiO2 nanoparticle layer grown by atomic layer deposition,” P hys,” Status Solidi RRL 3(2-3), 88–90 (2009). [CrossRef]

24.

J. G. Ma, Y. C. Liu, C. S. Xu, Y. X. Liu, C. L. Shao, H. Y. Xu, J. Y. Zhang, Y. M. Lu, D. Z. Shen, and X. W. Fan, “Preparation and characterization of ZnO particles embedded in SiO2 matrix by reactive magnetron sputtering,” J. Appl. Phys. 97(10), 103509 (2005). [CrossRef]

25.

M. J. Chen, Y. T. Shih, M. K. Wu, H. C. Chen, H. L. Tsai, W. C. Li, J. R. Yang, H. Kuan, and M. Shiojiri, “Structure and Ultraviolet Electroluminescence of n-ZnO/SiO2-ZnO Nanocomposite/p-GaN Heterostructure Light-Emitting Diodes,” IEEE Trans. Electron. Dev. 57(9), 2195–2202 (2010). [CrossRef]

26.

Y. T. Shih, M. K. Wu, W. C. Li, H. Kuan, J. R. Yang, M. Shiojiri, and M. J. Chen, “Amplified spontaneous emission from ZnO in n-ZnO/ZnO nanodots–SiO2 composite/p-AlGaN heterojunction light-emitting diodes,” Nanotechnology 20(16), 1–8 (2009). [CrossRef]

27.

I. Martil, E. Redondo, and A. Ojeda, “Influence of defects on the electrical and optical characteristics of blue light-emitting diodes on III-V nitrides,” J. Appl. Phys. 81(5), 2442–2444 (2007). [CrossRef]

OCIS Codes
(230.3670) Optical devices : Light-emitting diodes
(220.4241) Optical design and fabrication : Nanostructure fabrication

ToC Category:
Optical Devices

History
Original Manuscript: March 30, 2011
Revised Manuscript: May 14, 2011
Manuscript Accepted: May 23, 2011
Published: June 3, 2011

Citation
Jiun-Ting Chen, Wei-Chih Lai, Chi-Heng Chen, Ya-Yu Yang, Jinn-Kong Sheu, and Li-Wen Lai, "Electroluminescence of ZnO nanocrystal in sputtered ZnO-SiO2 nanocomposite light-emitting devices," Opt. Express 19, 11873-11879 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-12-11873


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References

  1. D. C. Look, “Doping and defects in ZnO, in ZnO bulk,” in Thin Films and Nanostructures, C. Jagadish and S. J. Pearton, (Elsevier, Oxford, 2006).
  2. D. M. Bagnall, Y. F. Chen, Z. Zhu, T. Yao, M. Y. Shen, and T. Goto, “High temperature excitonic stimulated emission from ZnO epitaxial layers,” Appl. Phys. Lett. 73(8), 1038–1040 (1998). [CrossRef]
  3. R. Hong, H. Qi, J. Huang, H. He, Z. Fan, and J. Shao, “Influence of oxygen partial pressure on the structure and photoluminescence of direct current reactive magnetron sputtering ZnO thin films,” Thin Solid Films 473(1), 58–62 (2005). [CrossRef]
  4. A. Tsukazaki, A. Ohtomo, T. Onuma, M. Ohtani, T. Makino, M. Sumiya, K. Ohtani, S. F. Chichibu, S. Fuke, Y. Segawa, H. Ohno, H. Koinuma, and M. Kawasaki, “Repeated temperature modulation epitaxy for p-type doping and light- emitting diode based on ZnO,” Nat. Mater. 4(1), 42–46 (2005). [CrossRef]
  5. S. Kim, F. Lugo, S. J. Pearton, D. P. Norton, Y.-L. Wang, and F. Ren, “Phosphorus doped ZnO light emitting diodes fabricated via pulsed laser deposition,” Appl. Phys. Lett. 92(11), 112108-112110(2008). [CrossRef]
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