OSA's Digital Library

Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 14 — Jul. 15, 2013
  • pp: 16578–16583
« Show journal navigation

Improvement of UV electroluminescence of n-ZnO/p-GaN heterojunction LED by ZnS interlayer

Lichun Zhang, Qingshan Li, Liang Shang, Feifei Wang, Chong Qu, and Fengzhou Zhao  »View Author Affiliations


Optics Express, Vol. 21, Issue 14, pp. 16578-16583 (2013)
http://dx.doi.org/10.1364/OE.21.016578


View Full Text Article

Acrobat PDF (2757 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

n-ZnO/p-GaN heterojunction light emitting diodes with different interfacial layers were fabricated by pulsed laser deposition. The electroluminescence (EL) spectra of the n-ZnO/p-GaN diodes display a broad blue-violet emission centered at 430 nm, whereas the n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN devices exhibit ultraviolet (UV) emission. Compared with the AlN interlayer, which is blocking both electron and hole at hetero-interface, the utilization of ZnS as intermediate layer can lower the barrier height for holes and keep an effective blocking for electron. Thus, an improved UV EL intensity and a low turn-on voltage (~5V) were obtained. The results were studied by peak-deconvolution with Gaussian functions and were discussed using the band diagram of heterojunctions.

© 2013 OSA

1. Introduction

Due to the wide direct band gap of 3.37 eV and large exciton binding energy of 60 meV at room temperature, zinc oxide (ZnO) has been considered to be a promising candidate material for optoelectronic applications, especially for blue to ultraviolet (UV) light emitting diode (LED) and UV detector devices [1

1. S. K. Jha, C. Luan, C. H. To, O. Kutsay, J. Kováč, J. A. Zapien, I. Bello, and S. T. Lee, “ZnO-nanorod-array/p-GaN high-performance ultra-violet light emitting devices prepared by simple solution synthesis,” Appl. Phys. Lett. 101(21), 211116 (2012). [CrossRef]

,2

2. T. S. Lin and C. T. Lee, “Performance investigation of p-i-n ZnO-based thin film homojunction ultraviolet photodetectors,” Appl. Phys. Lett. 101(22), 221118 (2012). [CrossRef]

]. Up to now, in spite of the great potential of ZnO in electron and photonic applications, there are few device applications, since it is difficult to obtain good and reproducible p-type ZnO [3

3. Y. S. Choi, J. W. Kang, D. K. Hwang, and S. J. Park, “Recent advances in ZnO-based light-emitting diodes,” IEEE Trans. Electron. Dev. 57(1), 26–41 (2010). [CrossRef]

]. As an alternative approach to homojunction, an n-ZnO/p-GaN heterojunction has been put forward as an attractive candidate for device applications, for ZnO and GaN have similar lattice structure and relatively small lattice mismatch [4

4. M. Y. Ke, T. C. Lu, S. C. Yang, C. P. Chen, Y. W. Cheng, L. Y. Chen, C. Y. Chen, J. H. He, and J. J. Huang, “UV light emission from GZO/ZnO/GaN heterojunction diodes with carrier confinement layers,” Opt. Express 17(25), 22912–22917 (2009). [CrossRef] [PubMed]

9

9. S. G. Zhang, X. W. Zhang, Z. G. Yin, J. X. Wang, J. J. Dong, Z. G. Wang, S. Qu, B. Cui, A. M. Wowchak, A. M. Dabiran, and P. P. Chow, “Improvement of electroluminescent performance of n-ZnO/AlN/p-GaN light-emitting diodes by optimizing the AlN barrier layer,” J. Appl. Phys. 109(9), 093708 (2011). [CrossRef]

]. Furthermore, according to the Anderson model, the conduction band offset (ΔEC) and valence band offset (ΔEV) of ZnO/GaN are determined to be 0.15 and 0.13 eV, nearly the same barrier heights for electrons and holes, which can lead to radiative recombination in both n-ZnO and p-GaN layers [10

10. J. B. You, X. W. Zhang, S. G. Zhang, J. X. Wang, Z. G. Yin, H. R. Tan, W. J. Zhang, P. K. Chu, B. Cui, A. M. Wowchak, A. M. Dabiran, and P. P. Chow, “Improved electroluminescence from n-ZnO/AlN/p-GaN heterojunction light-emitting diodes,” Appl. Phys. Lett. 96(20), 201102 (2010). [CrossRef]

]. However, the electroluminescence (EL) of the n-ZnO/p-GaN heterojunction LEDs emits mainly from the p-GaN instead of the n-ZnO, for the electron injection from n-ZnO would win over the hole injection from p-GaN because of the lower carrier concentration in p-GaN [11

11. Y. I. Alivov, J. E. Van 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]

]. In order to obtain the light emission from n-ZnO, it is required to block the electron injection from n-ZnO or promote the hole injection from p-GaN. To block the electron injection from ZnO, wide band gap materials such as MgO [12

12. H. Zhu, C. X. Shan, B. Yao, B. H. Li, J. Y. Zhang, Z. Z. Zhang, D. X. Zhao, D. Z. Shen, X. W. Fan, Y. M. Lu, and Z. K. Tang, “Ultralow-threshold laser realized in Zinc Oxide,” Adv. Mater. 21(16), 1613–1617 (2009). [CrossRef]

], AlN [10

10. J. B. You, X. W. Zhang, S. G. Zhang, J. X. Wang, Z. G. Yin, H. R. Tan, W. J. Zhang, P. K. Chu, B. Cui, A. M. Wowchak, A. M. Dabiran, and P. P. Chow, “Improved electroluminescence from n-ZnO/AlN/p-GaN heterojunction light-emitting diodes,” Appl. Phys. Lett. 96(20), 201102 (2010). [CrossRef]

], HfO2 [13

13. H. Huang, G. Fang, Y. Li, S. Li, X. Mo, H. Long, H. Wang, D. L. Carroll, and X. Zhao, “Improved and color tunable electroluminescence from n-ZnO/HfO2/p-GaN heterojunction light emitting diodes,” Appl. Phys. Lett. 100(23), 233502 (2012). [CrossRef]

], have been introduced into n-ZnO/p-GaN LEDs, because of the large conduction-band offsets (ΔEC) for MgO/ZnO (ΔEC = 3.55 eV), AlN/ZnO (ΔEC = 3.29 eV) and HfO2/ZnO (ΔEC = 2.29 eV) interfaces. Though the interfacial layers can effectively increase the barrier heights for electrons, high valence band offsets for MgO/GaN (ΔEV = 0.90 eV), AlN/GaN (ΔEV = 0.94 eV) and HfO2/GaN (ΔEV = 0.30 eV) interfaces would also increase the barrier heights for holes, leading to suppress the EL efficiency of devices.

Alternatively, ZnS, with the modest wide band gap (3.68eV) and large exciton binding energy of 40 meV, has similar fundamental physical properties with ZnO and GaN, including crystal structures, lattice constants, melting points, and so on [14

14. K. M. Yeung, W. S. Tsang, C. L. Mak, and K. H. Wong, “Optical studies of ZnS:Mn films grown by pulsed laser deposition,” J. Appl. Phys. 92(7), 3636–3640 (2002). [CrossRef]

,15

15. M. Y. Lu, J. H. Song, M. P. Lu, C. Y. Lee, L. J. Chen, and Z. L. Wang, “ZnO-ZnS heterojunction and ZnS nanowire arrays for electricity generation,” ACS Nano 3(2), 357–362 (2009). [CrossRef] [PubMed]

]. Therefore, it is possible to take ZnS as the interlayer to improve the performance of n-ZnO/p-GaN LEDs. In this study, the n-ZnO/p-GaN heterojunction LED with a 20 nm ZnS interlayer was fabricated by pulsed laser deposition (PLD). Compared with an n-ZnO/AlN/p-GaN heterojunction LED, significant improvement of ultraviolet EL was observed in n-ZnO/ZnS/p-GaN heterojunction LED.

2. Device fabrication

Figures 1(a)
Fig. 1 Schematic diagram of LEDs (a) without interlayer and with (b) ZnS and (c) AlN.
, 1(b) and 1(c) show three different structures of n-ZnO/p-GaN based heterojunction LEDs without interlayer and with ZnS and AlN interlayers. Commercial Mg-doped p-GaN epitaxial film produced by metal organic chemical vapor deposition (MOCVD) was used as the substrate. The hole concentration and mobility of p-GaN films were 1.6 × 1017 cm−3 and 14 cm2/Vs, respectively. For the n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN structure, 20 nm thick ZnS and AlN layer were deposited on the p-GaN substrate by PLD in vacuum environment (<10−6 Pa), followed by the deposition of 200 nm ZnO films in 10 Pa oxygen atmosphere. The substrate temperature was kept at 450°C and a KrF excimer laser (COMPexPro 201, Coherent Inc.) was employed operating with a wavelength of 248 nm. For comparison, another n-ZnO/p-GaN heterojunction LED without any interfacial layer was fabricated, and the growth conditions for the top n-ZnO films were the same as the former. Next, Pt (50nm)/Ti (30nm) and Pt (50nm)/Ni (30nm) contact layers, served as electrodes, were deposited on n-ZnO and p-GaN by PLD, respectively.

The x-ray diffraction (XRD) measurements were performed on Rigaku D/MAX2500V diffractometer with Cu Kα radiation. Photoluminescence (PL) spectra were excited by a 325 nm He-Cd laser (CVI Melles Griot) at room temperature. A monochromator (ARS SP2557) was employed for collecting the emission spectra of PL and EL. The I-V measurements were carried out with a Keithley 2611A source meter. The carrier concentration and Hall mobility of the ZnO films were investigated by Hall measurement (Accent HL5500 PC) with the van der Pauw method.

3. Results and discussion

The undoped ZnO films exhibit n-type conductivity with the electron concentration of 3.0 × 1018 cm−3 and mobility of 20.4 cm2/Vs. The I-V characteristics of all the n-ZnO/p-GaN heterojunction LEDs demonstrate a nonlinear rectifying behavior, as shown in Fig. 2(a)
Fig. 2 (a) I-V curves and (b) XRD pattern of the LED devices. The inset in Fig. 2(a) shows the I-V curves of Pt/Ni and Pt/Ti ohmic contact on p-GaN and n-ZnO.
. Compared with the n-ZnO/p-GaN heterojunction LED, an additional voltage drop across the intermediate layer is observed from the n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN device. In addition, it can be found that the forward turn-on voltage of n-ZnO/AlN/p-GaN (~6.5V) heterojunction is higher than that of n-ZnO/ZnS/p-GaN (~5V), for the dielectric constant of the AlN layer is larger than that of the ZnS layer [16

16. J. M. Siqueiros, R. Machorro, and L. E. Regalado, “Determination of the optical constants of MgF2 and ZnS from spectrophotometric measurements and the classical oscillator method,” Appl. Opt. 27(12), 2549–2553 (1988). [CrossRef] [PubMed]

,17

17. N. Sinha, G. E. Wabiszewski, R. Mahameed, V. V. Felmetsger, S. M. Tanner, R. W. Carpick, and G. Piazza, “Piezoelectric aluminum nitride nanoelectromechanical actuators,” Appl. Phys. Lett. 95(5), 053106 (2009). [CrossRef]

]. The linear curves in the inset of Fig. 2(a) from both the Pt/Ni on p-GaN and Pt/Ti on n-ZnO reveal good Ohmic contacts at both electrodes, inferring that the rectifying behavior of the LEDs originates from the n-ZnO/p-GaN heterojunction. XRD patterns of the heterojunction LEDs are shown in Fig. 2(b). For all the samples, two diffraction peaks at ~33.9° and ~34.0°, which are corresponding to the ZnO(002) and GaN (002), confirm that the ZnO/GaN heterojunction are strongly c-axis orientation. Furthermore, two additional peaks at ~28.4° and ~36.2° are also found in the XRD patterns of the ZnO/ZnS/p-GaN and ZnO/AlN/p-GaN LEDs, which are corresponding to the wurtzite ZnS(002) (JCPDS card No. 36-1450) and AlN(002) (JCPDS card No. 25-1133).

The EL spectra of the n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN heterojunction diodes are shown in Figs. 4(a)
Fig. 4 EL spectrum of (a) n-ZnO/ZnS/p-GaN and (b) n-ZnO/AlN/p-GaN heterojunction LED. (c) The FWHM of EL spectra of two LEDs with different injection currents. (d) The EL integrated intensity of two LEDs as a function of the input power.
and 4(b). With the injection currents increasing from 0.4 mA to 2.0 mA, all the EL spectra of the n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN heterojunction diodes display typical near-UV emission peaks at around 381nm. Although all the peaks of these EL spectra center around the NBE emission of ZnO films, the EL spectra present different profiles. Figure 4(c) plots the full width at half maximum (FWHM) of the EL spectra of the n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN diodes with different injection currents. As the injection currents increased from 0.4 to 2.0mA, the FWHM of n-ZnO/ZnS/p-GaN narrowed from 68.9 nm to 31.8 nm, while the FWHM of n-ZnO/AlN/p-GaN narrowed from 33.9 nm to 27.5 nm. Compared with the n-ZnO/AlN/p-GaN heterojunction LED, the EL spectra of n-ZnO/ZnS/p-GaN heterojunction LED show a much broader emission band. Figure 4(d) shows the curves of integrated EL intensity versus input power for the n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN heterojunction diodes. The EL integrated intensities of the n-ZnO/ZnS/p-GaN LED are obviously both higher than that of the n-ZnO/AlN/p-GaN LED at the same input power, which indicates that the ZnS films can effectively improve the EL efficiency of n-ZnO/p-GaN heterojunction diodes.

In order to better understand the origin of the EL emission, a Gaussian function is exploited to simulate the EL spectra of the n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN heterojunction diodes with injection currents of 2.0 mA, as shown in Fig. 5
Fig. 5 Gaussian deconvolution for EL spectra of the n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN heterojunction diodes. Insets show the energy band diagram of heterojunction LEDs.
. The simulated EL spectrum of the n-ZnO/ZnS/p-GaN diode consists of three distinct bands centered at around 380nm, 397nm and 430nm. Compared with PL spectra in Fig. 3(a), the UV emission band centered at around 380 nm is attributed to the NBE of ZnO films, whereas the blue emission band centered at about 430 nm should be ascribed to the transitions from the conduction band or shallow donors to deep Mg acceptor levels in the p-GaN substrates. And the violet emission centered at 397nm, which has been widely investigated in the ZnO-based diodes, is probably attributed to the shallow donors to the valence band or donor-acceptor pair recombination in ZnO [22

22. G. Y. Zhu, C. X. Xu, Y. Lin, Z. L. Shi, J. T. Li, T. Ding, Z. S. Tian, and G. F. Chen, “Ultraviolet electroluminescence from horizontal ZnO microrods/GaN heterojunction light-emitting diode array,” Appl. Phys. Lett. 101(4), 041110 (2012). [CrossRef]

,23

23. S. Xu, C. Xu, Y. Liu, Y. F. Hu, R. S. Yang, Q. Yang, J. H. Ryou, H. J. Kim, Z. Lochner, S. Choi, R. Dupuis, and Z. L. Wang, “Ordered nanowire array blue/near-UV light emitting diodes,” Adv. Mater. 22(42), 4749–4753 (2010). [CrossRef] [PubMed]

]. According to Fig. 5, the EL spectrum of the n-ZnO/AlN/p-GaN diode exhibits two subbands centered at around 381nm and 397nm. It is worth noting that no blue emission band is observed in the EL spectra of the n-ZnO/AlN/p-GaN diodes.

The radiative recombination processes are illustrated with energy band diagram in the insets of Fig. 5. Electron affinity energies of ZnS and AlN are assumed to be 3.9 and 0.6 eV, respectively [10

10. J. B. You, X. W. Zhang, S. G. Zhang, J. X. Wang, Z. G. Yin, H. R. Tan, W. J. Zhang, P. K. Chu, B. Cui, A. M. Wowchak, A. M. Dabiran, and P. P. Chow, “Improved electroluminescence from n-ZnO/AlN/p-GaN heterojunction light-emitting diodes,” Appl. Phys. Lett. 96(20), 201102 (2010). [CrossRef]

,15

15. M. Y. Lu, J. H. Song, M. P. Lu, C. Y. Lee, L. J. Chen, and Z. L. Wang, “ZnO-ZnS heterojunction and ZnS nanowire arrays for electricity generation,” ACS Nano 3(2), 357–362 (2009). [CrossRef] [PubMed]

]. In addition, the bandgap energy of ZnS is taken to be about 3.68 eV and that of AlN is assumed to be 6.2 eV. For the n-ZnO/AlN/p-GaN heterojuniction under forward bias, electrons are confined in the ZnO layer by the large electron barrier height at the AlN/ZnO interface (ΔEC = 3.75eV). As a result, the blue emission form GaN is almost undetectable in the n-ZnO/AlN/p-GaN LED. However, as the electron barrier height at ZnS/ZnO interface (ΔEC = 0.45eV) is smaller than that of the AlN/ZnO interface, some of the electrons would inject from n-ZnO to p-GaN and the blue emission has been observed merely in n-ZnO/ZnS/p-GaN diode.

On the other hand, at the interface between dielectric interlayer and GaN, the holes can fluently transfer from GaN to either AlN or ZnS under forward bias because of the formation of potential well, as shown in the insets of Fig. 5. Consequently, holes in the GaN layer can inject to the ZnO layer due to the lower hole barrier height at the dielectric/ZnO interface(ΔEV = 0.92eV for AlN/ZnO interface and 0.14eV for ZnS/ZnO interface). Therefore, the radiative recombination would take place in the ZnO layer. Furthermore, the hole barrier height at the ZnS/ZnO interfaces (0.14 eV) is almost the same as that of the GaN/ZnO interface (0.13 eV), which is far smaller than the hole barrier height of the AlN/ZnO interfaces (0.92 eV). As the much smaller hole barrier height can make hole injection from GaN to ZnO more easily, the possibility of radiative recombination in ZnO has been enhanced in the n-ZnO/ZnS/p-GaN diode, which is the very reason that the EL intensity of n-ZnO/ZnS/p-GaN diode is higher than that of n-ZnO/AlN/p-GaN diode.

4. Summary

In summary, n-ZnO/p-GaN heterojunction LEDs with different interfacial layers have been fabricated by PLD. Having inserted a thin ZnS and AlN intermediate layer into the device, the EL spectra of n-ZnO/ZnS/p-GaN and n-ZnO/AlN/p-GaN heterojunction diodes exhibit a typical near-UV emission peak. Though the EL spectra of n-ZnO/ZnS/p-GaN display a weaker blue emission band due to the smaller electron barrier height in ZnS/ZnO interface, the EL intensity of n-ZnO/ZnS/p-GaN heterojunction LED has been improved due to a much smaller hole barrier height at ZnO/ZnS interfaces. The present work provides a feasible method for improving the EL performance of ZnO/p-GaN heterojunction LEDs.

Acknowledgments

The authors wish to acknowledge the financial support of the National Natural Science Foundation of China (No. 11144010), Natural Science Foundation of Shandong Province (No.ZR2010AL026) and the project of Shandong Province Higher Educational Science and Technology Program (No. J12LJ03).

References and links

1.

S. K. Jha, C. Luan, C. H. To, O. Kutsay, J. Kováč, J. A. Zapien, I. Bello, and S. T. Lee, “ZnO-nanorod-array/p-GaN high-performance ultra-violet light emitting devices prepared by simple solution synthesis,” Appl. Phys. Lett. 101(21), 211116 (2012). [CrossRef]

2.

T. S. Lin and C. T. Lee, “Performance investigation of p-i-n ZnO-based thin film homojunction ultraviolet photodetectors,” Appl. Phys. Lett. 101(22), 221118 (2012). [CrossRef]

3.

Y. S. Choi, J. W. Kang, D. K. Hwang, and S. J. Park, “Recent advances in ZnO-based light-emitting diodes,” IEEE Trans. Electron. Dev. 57(1), 26–41 (2010). [CrossRef]

4.

M. Y. Ke, T. C. Lu, S. C. Yang, C. P. Chen, Y. W. Cheng, L. Y. Chen, C. Y. Chen, J. H. He, and J. J. Huang, “UV light emission from GZO/ZnO/GaN heterojunction diodes with carrier confinement layers,” Opt. Express 17(25), 22912–22917 (2009). [CrossRef] [PubMed]

5.

J. T. Chen, W. C. Lai, C. H. Chen, Y. Y. Yang, J. K. Sheu, and L. W. Lai, “Electroluminescence of ZnO nanocrystal in sputtered ZnO-SiO2 nanocomposite light-emitting devices,” Opt. Express 19(12), 11873–11879 (2011). [CrossRef] [PubMed]

6.

S. G. Zhang, X. W. Zhang, F. T. Si, J. J. Dong, J. X. Wang, X. Liu, Z. G. Yin, and H. L. Gao, “Ordered ZnO nanorods-based heterojunction light-emitting diodes with graphene current spreading layer,” Appl. Phys. Lett. 101(12), 121104 (2012). [CrossRef]

7.

J. Ye, Y. Zhao, L. B. Tang, L. M. Chen, C. M. Luk, S. F. Yu, S. T. Lee, and S. P. Lau, “Ultraviolet electroluminescence from two-dimensional ZnO nanomesh/GaN heterojunction light emitting diodes,” Appl. Phys. Lett. 98(26), 263101 (2011). [CrossRef]

8.

X. M. Zhang, M. Y. Lu, Y. Zhang, L. J. Chen, and Z. L. Wang, “Fabrication of a high-brightness blue-light-emitting diode using a ZnO-nanowire array grown on p-GaN thin Film,” Adv. Mater. 21(27), 2767–2770 (2009). [CrossRef]

9.

S. G. Zhang, X. W. Zhang, Z. G. Yin, J. X. Wang, J. J. Dong, Z. G. Wang, S. Qu, B. Cui, A. M. Wowchak, A. M. Dabiran, and P. P. Chow, “Improvement of electroluminescent performance of n-ZnO/AlN/p-GaN light-emitting diodes by optimizing the AlN barrier layer,” J. Appl. Phys. 109(9), 093708 (2011). [CrossRef]

10.

J. B. You, X. W. Zhang, S. G. Zhang, J. X. Wang, Z. G. Yin, H. R. Tan, W. J. Zhang, P. K. Chu, B. Cui, A. M. Wowchak, A. M. Dabiran, and P. P. Chow, “Improved electroluminescence from n-ZnO/AlN/p-GaN heterojunction light-emitting diodes,” Appl. Phys. Lett. 96(20), 201102 (2010). [CrossRef]

11.

Y. I. Alivov, J. E. Van 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]

12.

H. Zhu, C. X. Shan, B. Yao, B. H. Li, J. Y. Zhang, Z. Z. Zhang, D. X. Zhao, D. Z. Shen, X. W. Fan, Y. M. Lu, and Z. K. Tang, “Ultralow-threshold laser realized in Zinc Oxide,” Adv. Mater. 21(16), 1613–1617 (2009). [CrossRef]

13.

H. Huang, G. Fang, Y. Li, S. Li, X. Mo, H. Long, H. Wang, D. L. Carroll, and X. Zhao, “Improved and color tunable electroluminescence from n-ZnO/HfO2/p-GaN heterojunction light emitting diodes,” Appl. Phys. Lett. 100(23), 233502 (2012). [CrossRef]

14.

K. M. Yeung, W. S. Tsang, C. L. Mak, and K. H. Wong, “Optical studies of ZnS:Mn films grown by pulsed laser deposition,” J. Appl. Phys. 92(7), 3636–3640 (2002). [CrossRef]

15.

M. Y. Lu, J. H. Song, M. P. Lu, C. Y. Lee, L. J. Chen, and Z. L. Wang, “ZnO-ZnS heterojunction and ZnS nanowire arrays for electricity generation,” ACS Nano 3(2), 357–362 (2009). [CrossRef] [PubMed]

16.

J. M. Siqueiros, R. Machorro, and L. E. Regalado, “Determination of the optical constants of MgF2 and ZnS from spectrophotometric measurements and the classical oscillator method,” Appl. Opt. 27(12), 2549–2553 (1988). [CrossRef] [PubMed]

17.

N. Sinha, G. E. Wabiszewski, R. Mahameed, V. V. Felmetsger, S. M. Tanner, R. W. Carpick, and G. Piazza, “Piezoelectric aluminum nitride nanoelectromechanical actuators,” Appl. Phys. Lett. 95(5), 053106 (2009). [CrossRef]

18.

H. B. Zeng, G. T. Duan, Y. Li, S. K. Yang, X. X. Xu, and W. P. Cai, “Blue Luminescence of ZnO Nanoparticles Based on Non-Equilibrium Processes: Defect Origins and Emission Controls,” Adv. Funct. Mater. 20(4), 561–572 (2010). [CrossRef]

19.

Y. Y. Gong, T. Andelman, G. F. Neumark, S. O’Brien, and I. L. Kuskovsky, “Origin of defect-related green emission from ZnO nanoparticles: effect of surface modification,” Nanoscale Res. Lett. 2(6), 297–302 (2007). [CrossRef]

20.

S. Nakamura, T. Mukai, and M. Senon, “High-power GaN p-n junction blue-light-emitting diodes,” Jpn. J. Appl. Phys. 30(Part 2, No. 12A), L1998–L2001 (1991). [CrossRef]

21.

M. A. Khan, R. A. Qchen, Skogman, and J. N. Kuznia, “Violet-blue GaN homojunction light emitting diodes with rapid thermal annealed p-type layers,” Appl. Phys. Lett. 66(16), 2046–2047 (1995).

22.

G. Y. Zhu, C. X. Xu, Y. Lin, Z. L. Shi, J. T. Li, T. Ding, Z. S. Tian, and G. F. Chen, “Ultraviolet electroluminescence from horizontal ZnO microrods/GaN heterojunction light-emitting diode array,” Appl. Phys. Lett. 101(4), 041110 (2012). [CrossRef]

23.

S. Xu, C. Xu, Y. Liu, Y. F. Hu, R. S. Yang, Q. Yang, J. H. Ryou, H. J. Kim, Z. Lochner, S. Choi, R. Dupuis, and Z. L. Wang, “Ordered nanowire array blue/near-UV light emitting diodes,” Adv. Mater. 22(42), 4749–4753 (2010). [CrossRef] [PubMed]

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

ToC Category:
Optical Devices

History
Original Manuscript: May 7, 2013
Revised Manuscript: June 12, 2013
Manuscript Accepted: June 12, 2013
Published: July 2, 2013

Citation
Lichun Zhang, Qingshan Li, Liang Shang, Feifei Wang, Chong Qu, and Fengzhou Zhao, "Improvement of UV electroluminescence of n-ZnO/p-GaN heterojunction LED by ZnS interlayer," Opt. Express 21, 16578-16583 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-14-16578


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. S. K. Jha, C. Luan, C. H. To, O. Kutsay, J. Kováč, J. A. Zapien, I. Bello, and S. T. Lee, “ZnO-nanorod-array/p-GaN high-performance ultra-violet light emitting devices prepared by simple solution synthesis,” Appl. Phys. Lett.101(21), 211116 (2012). [CrossRef]
  2. T. S. Lin and C. T. Lee, “Performance investigation of p-i-n ZnO-based thin film homojunction ultraviolet photodetectors,” Appl. Phys. Lett.101(22), 221118 (2012). [CrossRef]
  3. Y. S. Choi, J. W. Kang, D. K. Hwang, and S. J. Park, “Recent advances in ZnO-based light-emitting diodes,” IEEE Trans. Electron. Dev.57(1), 26–41 (2010). [CrossRef]
  4. M. Y. Ke, T. C. Lu, S. C. Yang, C. P. Chen, Y. W. Cheng, L. Y. Chen, C. Y. Chen, J. H. He, and J. J. Huang, “UV light emission from GZO/ZnO/GaN heterojunction diodes with carrier confinement layers,” Opt. Express17(25), 22912–22917 (2009). [CrossRef] [PubMed]
  5. J. T. Chen, W. C. Lai, C. H. Chen, Y. Y. Yang, J. K. Sheu, and L. W. Lai, “Electroluminescence of ZnO nanocrystal in sputtered ZnO-SiO2 nanocomposite light-emitting devices,” Opt. Express19(12), 11873–11879 (2011). [CrossRef] [PubMed]
  6. S. G. Zhang, X. W. Zhang, F. T. Si, J. J. Dong, J. X. Wang, X. Liu, Z. G. Yin, and H. L. Gao, “Ordered ZnO nanorods-based heterojunction light-emitting diodes with graphene current spreading layer,” Appl. Phys. Lett.101(12), 121104 (2012). [CrossRef]
  7. J. Ye, Y. Zhao, L. B. Tang, L. M. Chen, C. M. Luk, S. F. Yu, S. T. Lee, and S. P. Lau, “Ultraviolet electroluminescence from two-dimensional ZnO nanomesh/GaN heterojunction light emitting diodes,” Appl. Phys. Lett.98(26), 263101 (2011). [CrossRef]
  8. X. M. Zhang, M. Y. Lu, Y. Zhang, L. J. Chen, and Z. L. Wang, “Fabrication of a high-brightness blue-light-emitting diode using a ZnO-nanowire array grown on p-GaN thin Film,” Adv. Mater.21(27), 2767–2770 (2009). [CrossRef]
  9. S. G. Zhang, X. W. Zhang, Z. G. Yin, J. X. Wang, J. J. Dong, Z. G. Wang, S. Qu, B. Cui, A. M. Wowchak, A. M. Dabiran, and P. P. Chow, “Improvement of electroluminescent performance of n-ZnO/AlN/p-GaN light-emitting diodes by optimizing the AlN barrier layer,” J. Appl. Phys.109(9), 093708 (2011). [CrossRef]
  10. J. B. You, X. W. Zhang, S. G. Zhang, J. X. Wang, Z. G. Yin, H. R. Tan, W. J. Zhang, P. K. Chu, B. Cui, A. M. Wowchak, A. M. Dabiran, and P. P. Chow, “Improved electroluminescence from n-ZnO/AlN/p-GaN heterojunction light-emitting diodes,” Appl. Phys. Lett.96(20), 201102 (2010). [CrossRef]
  11. Y. I. Alivov, J. E. Van 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]
  12. H. Zhu, C. X. Shan, B. Yao, B. H. Li, J. Y. Zhang, Z. Z. Zhang, D. X. Zhao, D. Z. Shen, X. W. Fan, Y. M. Lu, and Z. K. Tang, “Ultralow-threshold laser realized in Zinc Oxide,” Adv. Mater.21(16), 1613–1617 (2009). [CrossRef]
  13. H. Huang, G. Fang, Y. Li, S. Li, X. Mo, H. Long, H. Wang, D. L. Carroll, and X. Zhao, “Improved and color tunable electroluminescence from n-ZnO/HfO2/p-GaN heterojunction light emitting diodes,” Appl. Phys. Lett.100(23), 233502 (2012). [CrossRef]
  14. K. M. Yeung, W. S. Tsang, C. L. Mak, and K. H. Wong, “Optical studies of ZnS:Mn films grown by pulsed laser deposition,” J. Appl. Phys.92(7), 3636–3640 (2002). [CrossRef]
  15. M. Y. Lu, J. H. Song, M. P. Lu, C. Y. Lee, L. J. Chen, and Z. L. Wang, “ZnO-ZnS heterojunction and ZnS nanowire arrays for electricity generation,” ACS Nano3(2), 357–362 (2009). [CrossRef] [PubMed]
  16. J. M. Siqueiros, R. Machorro, and L. E. Regalado, “Determination of the optical constants of MgF2 and ZnS from spectrophotometric measurements and the classical oscillator method,” Appl. Opt.27(12), 2549–2553 (1988). [CrossRef] [PubMed]
  17. N. Sinha, G. E. Wabiszewski, R. Mahameed, V. V. Felmetsger, S. M. Tanner, R. W. Carpick, and G. Piazza, “Piezoelectric aluminum nitride nanoelectromechanical actuators,” Appl. Phys. Lett.95(5), 053106 (2009). [CrossRef]
  18. H. B. Zeng, G. T. Duan, Y. Li, S. K. Yang, X. X. Xu, and W. P. Cai, “Blue Luminescence of ZnO Nanoparticles Based on Non-Equilibrium Processes: Defect Origins and Emission Controls,” Adv. Funct. Mater.20(4), 561–572 (2010). [CrossRef]
  19. Y. Y. Gong, T. Andelman, G. F. Neumark, S. O’Brien, and I. L. Kuskovsky, “Origin of defect-related green emission from ZnO nanoparticles: effect of surface modification,” Nanoscale Res. Lett.2(6), 297–302 (2007). [CrossRef]
  20. S. Nakamura, T. Mukai, and M. Senon, “High-power GaN p-n junction blue-light-emitting diodes,” Jpn. J. Appl. Phys.30(Part 2, No. 12A), L1998–L2001 (1991). [CrossRef]
  21. M. A. Khan, R. A. Qchen, Skogman, and J. N. Kuznia, “Violet-blue GaN homojunction light emitting diodes with rapid thermal annealed p-type layers,” Appl. Phys. Lett.66(16), 2046–2047 (1995).
  22. G. Y. Zhu, C. X. Xu, Y. Lin, Z. L. Shi, J. T. Li, T. Ding, Z. S. Tian, and G. F. Chen, “Ultraviolet electroluminescence from horizontal ZnO microrods/GaN heterojunction light-emitting diode array,” Appl. Phys. Lett.101(4), 041110 (2012). [CrossRef]
  23. S. Xu, C. Xu, Y. Liu, Y. F. Hu, R. S. Yang, Q. Yang, J. H. Ryou, H. J. Kim, Z. Lochner, S. Choi, R. Dupuis, and Z. L. Wang, “Ordered nanowire array blue/near-UV light emitting diodes,” Adv. Mater.22(42), 4749–4753 (2010). [CrossRef] [PubMed]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

Figures

Fig. 1 Fig. 2 Fig. 3
 
Fig. 4 Fig. 5
 

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited