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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 1 — Jan. 14, 2013
  • pp: 391–403
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Mutlicolor electroluminescent Si quantum dots embedded in SiOx thin film MOSLED with 2.4% external quantum efficiency

Chih-Hsien Cheng, Yu-Chung Lien, Chung-Lun Wu, and Gong-Ru Lin  »View Author Affiliations


Optics Express, Vol. 21, Issue 1, pp. 391-403 (2013)
http://dx.doi.org/10.1364/OE.21.000391


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Abstract

The enhanced recombination and external quantum efficiency (EQE) of the multi-color metal-oxide-semiconductor light-emitting diodes (MOSLEDs) made on the SiOx film with buried Si quantum dots (Si-QDs) grown by plasma-enhanced chemical vapor deposition are demonstrated. By shrinking Si-QD size from 4.2 to 1.8 nm with increasing RF plasma power from 20 to 50 W, these MOSLEDs enhance the maximal electroluminescent (EL) power from 0.1 to 0.7 μW. This is mainly attributed to the enhanced recombination rate by enlarging the overlap between electron and hole wave-functions. As evidence, the photoluminescent lifetime is significantly shortened from 5 µs to 0.31µs due to the enhanced direct recombination in smaller Si-QDs. The corresponding power-current slope and EQE are observed to increase from 0.09 to 5.7 mW/A and from 1.9 × 10−5 to 2.4%, respectively. The EL enhancement originates from shorter wavelength and stronger carrier confinement within Si-QDs with smaller size, as confirmed by the increased barrier height at the ITO/SiOx:Si-QD interface from 1.05 to 3.62 eV. The smaller and denser Si-QDs result in a current endurance to operate the MOSLED at breakdown edge with highest power conversion efficiency, thus providing a maximal blue-light EL power at 0.7 μW with the highest EQE of 2.4%.

© 2013 OSA

1. Introduction

Recently, the research has been emphasized on the SiOx based MOSLEDs with broadband tunable EL wavelengths in visible region. Furthermore, the MOSLEDs with different matrices, such as SiNx, SiOxNy, etc, are demonstrated to enhance the carrier injection because these matrices have the lower barrier height [17

17. M. Wang, J. Huang, Z. Yuan, A. Anopchenko, D. Li, D. Yang, and L. Pavesi, “Light emission properties and mechanism of low-temperature prepared amorphous SiNx films. II. Defect states electroluminescence,” J. Appl. Phys. 104(8), 083505 (2008). [CrossRef]

20

20. D. Li, F. Wang, D. Yang, and D. Que, “Electrically tunable electroluminescence from SiNx-based light-emitting devices,” Opt. Express 20(16), 17359–17366 (2012). [CrossRef] [PubMed]

]. The external quantum efficiency (EQE) of MOSLEDs suffers from a limited tunneling probability of carriers passing through the SiOx matrix. The EQE of Si-QD embedded in MOSLEDs of up to 0.2% was reported by several groups [21

21. N. Lalic and J. Linnros, “Characterization of a porous silicon diode with efficient and tunable electroluminescence,” J. Appl. Phys. 80(10), 5971–5977 (1996). [CrossRef]

24

24. G.-R. Lin, C.-J. Lin, H.-C. Kuo, H.-S. Lin, and C.-C. Kuo, “Anomalous microphotoluminescence of high-aspect-ratio Si nanopillars formatted by dry-etching Si substrate with self-aggregated Ni nanodot mask,” Appl. Phys. Lett. 90(14), 143102 (2007). [CrossRef]

]. Marconi’s group employed the nanocrystalline-Si/SiO2 multilayers to fabricate the LEDs. The EQE of these devices is 0.2% with an operating voltage of 36 V [22

22. A. Marconi, A. Anopchenko, M. Wang, G. Pucker, P. Bellutti, and L. Pavesi, “High power efficiency in Si-nc/SiO2 multilayer light emitting devices by bipolar direct tunneling,” Appl. Phys. Lett. 94(22), 221110 (2009). [CrossRef]

]. Lin and associates used Si nanopillars to enhance the Fowler-Nordeim tunneling and reduce the effective barrier height, providing that the EQE of MOSLEDs is up to 0.1% [23

23. G.-R. Lin, C.-J. Lin, and H.-C. Kuo, “Improving carrier transport and light emission in a silicon-nanocrystal based MOS light-emitting diode on silicon nanopillar array,” Appl. Phys. Lett. 91(9), 093122 (2007). [CrossRef]

]. In addition, they also detuned the size of Ni nanodots as the metal mask to form the different-sized Si nanopillars which control the PL wavelength ranging from 826 nm, to 874 nm [24

24. G.-R. Lin, C.-J. Lin, H.-C. Kuo, H.-S. Lin, and C.-C. Kuo, “Anomalous microphotoluminescence of high-aspect-ratio Si nanopillars formatted by dry-etching Si substrate with self-aggregated Ni nanodot mask,” Appl. Phys. Lett. 90(14), 143102 (2007). [CrossRef]

]. Under the pulse operation, Nishimura and associates reported a maximal EQE of up to 0.8% [25

25. K. Nishimura, Y. Nagao, and N. Ikeda, “High external quantum efficiency of electroluminescence from photoanodized porous silicon,” Jpn. J. Appl. Phys. 37(Part 2 No. 3B), L303–L305 (1998). [CrossRef]

]. Gelloz et al. further observed that the EQE of LEDs with the buried Si-QDs under the continuous-wave operation can be enhanced up to 1.1% by the post-anodized electrochemical oxidation of porous silicon [26

26. B. Gelloz and N. Koshida, “Electroluminescence with high and stable quantum efficiency and low threshold voltage from anodically oxidized thin porous silicon diode,” J. Appl. Phys. 88(7), 4319–4324 (2000). [CrossRef]

]. The EQE of up to 0.2% for the graded Si-QD LEDs with the Si-QD/SiO2 multilayer is achieved by Anopchenko et al. [27

27. A. Anopchenko, A. Marconi, M. Wang, G. Pucker, P. Bellutti, and L. Pavesi, “Graded-size Si quantum dot ensembles for efficient light-emitting diodes,” Appl. Phys. Lett. 99(18), 181108 (2011). [CrossRef]

]. Per’alvarez’s group observed that the EQE of MOSLEDs with the Si-rich SiOx film grown by ion implantation and PECVD are 10−3% and 0.1%, respectively [28

28. M. Perálvarez, J. Barreto, J. Carreras, A. Morales, D. Navarro-Urrios, Y. Lebour, C. Domínguez, and B. Garrido, “Si-nanocrystal-based LEDs fabricated by ion implantation and plasma-enhanced chemical vapour deposition,” Nanotechnology 20(40), 405201 (2009). [CrossRef] [PubMed]

]. In addition, the recent work further reported that pointed that the higher barrier height at the ITO/SiOx:Si-QD interface and the lower capacity of carrier storage within Si-QDs for MOSLEDs could be prompt their power conversion ratio to 2.35 × 10−2% [29

29. B.-H. Lai, C.-H. Cheng, and G.-R. Lin, “Multicolor ITO/SiOx/p-Si/Al light emitting diodes with improved emission efficiency by small Si quantum dots,” IEEE J. Quantum Electron. 47(5), 698–704 (2011). [CrossRef]

]. Lin and associates further employed the nano-structures, such as nano-pillars, nano-pyramids, etc., to enhance the EL intensity of MOSLEDs [30

30. G.-R. Lin, Y.-H. Pai, and C.-T. Lin, “Microwatt MOSLED using SiOx with buried Si nanocrystals on Si nano-pillar array,” J. Lightwave Technol. 26(11), 1486–1491 (2008). [CrossRef]

, 31

31. Y.-C. Lien, Y.-H. Pai, and G.-R. Lin, “Si nano-dots and nano-pyramids dependent light emission and charge accumulation in ITO/SiOx/p-Si MOS diode,” IEEE J. Quantum Electron. 46(1), 121–127 (2010). [CrossRef]

]. The EQE of MOSLEDs with an n-ZnO/SiO2-Si QDs-SiO2/p-Si heterostructure is improved up to 4.3 × 10−2% by Sun’s group [32

32. E. Sun, F.-H. Su, Y.-T. Shih, H.-L. Tsai, C.-H. Chen, M.-K. Wu, J.-R. Yang, and M.-J. Chen, “An efficient Si light-emitting diode based on an n-ZnO/SiO2-Si nanocrystals-SiO2/p-Si heterostructure,” Nanotechnology 20(44), 445202 (2009). [CrossRef] [PubMed]

]. More recently, the EQE of Si-QD related EL device has been improved to 8.6% by using the organic layer as a host matrix [33

33. K.-Y. Cheng, R. Anthony, U. R. Kortshagen, and R. J. Holmes, “High-efficiency silicon nanocrystal light-emitting devices,” Nano Lett. 11(5), 1952–1956 (2011). [CrossRef] [PubMed]

, 34

34. D. P. Puzzo, E. J. Henderson, M. G. Helander, Z. B. Wang, G. A. Ozin, and Z. Lu, “Visible colloidal nanocrystal silicon light-emitting diode,” Nano Lett. 11(4), 1585–1590 (2011). [CrossRef] [PubMed]

].

2. Experiment setup

3. Results and discussion

Under forward bias, the electrons and holes inject into Si-QDs by F-N tunneling through the Si-rich SiOx host matrix from ITO and p-Si substrate, respectively. With the RF power increasing from 20 to 50 W, the turn-on electric field increases from 3.2 to 9.2 MV/cm and from 2.6 to 8.8 MV/cm after annealing for 2.5 and 90 min, respectively. The increasing Si-QD size could lead to an enhancement of the tunneling current. That is, the lower turn-on electric field is observed in MOSLEDs with enlarged Si-QDs. The compliance voltage dropped by lengthening the annealing time of SiOx film before fabricating MOSLEDs, which originates from the thickness shrinkage of SiOx film after long-term annealing. By defining a transmission coefficient of T(Ex) as a function of the energy Ex incident on the barrier at metal/oxide interface, and then summing up over all possible energies using the Wentzel-Kramers-Brillouin (WKB) approximation in the absence of Schottky effect with xti = 0Å (with ignored temperature variation and barrier shrinkage), the F-N tunneling current density, JF-N, can be expressed as [38

38. R. H. Fowler and L. Nordheim, “Electron emission in intense electric fields,” Proc. R. Soc. Lond., A Contain. Pap. Math. Phys. Character 119(781), 173–181 (1928). [CrossRef]

]:
JFN=4πqm0η3Exe2xtixtx(2moxη2)1/2[(qΨ(x)Ex)1/2]dxdExEx+f(Ex,T)dE=q3(m0/mox)8πhϕBE2exp(8π2moxϕB33qhE)=1.54×106(m0/mox)ϕBE2exp(6.83×1072(mox/m0)/ϕB3E),
(1)
where mo denotes the free electron mass, T the temperature, f (Ex,T) the Fermi Dirac function, E the electric field in SiOx layer, and Φm the potential barrier at metal/oxide interface, mox the effective mass of electron in SiOx (mox = 0.5m0), h the reduced Planck constant, qΨ(x) the potential barrier in SiOx layer at x abscissa, q the electron charge, and xtx-xti the tunnel distance in SiOx layer. As a result, the turn-on electric field and barrier height shown in Fig. 2
Fig. 2 (a) The F-N plot of ln(JG/E2) dependent electric field as a function of RF power with their SiOx annealing at 2.5 (upper) and 90 min (lower). (b) Barrier height (black line) and turn-on electric field (blue line) of the MOSLEDs with 2.5-min (square patterns with linked dashed line) and 90-min (circle patterns with linked solid line) annealed SiOx samples grown at different RF plasma powers.
can be extracted from the ln(JF-N/E2) vs. E plot, in which the intersection point of two fitted lines represents the turn-on electric field and the barrier height can be calculated from the descending slope.

With a forward (positive) bias applied from Al contact (p-type Si) to ITO contact (SiOx gate), electrons are injected from ITO gate contact and holes are injected from Al contact of the MOSLED device operated at an accumulation condition. With a relatively large bias added at p-type Si side, the band diagram of MOSLEDs is analogous to that of the p-type MOS diode operated at the accumulation state, as shown in Fig. 3
Fig. 3 The band diagram of MOSLEDs grown at an RF plasma power of 50 W. Inset: The variations on the band diagram of the MOSLEDs grown at different RF plasma power.
. With increasing RF plasma powers, the enhancing turn-on electric field accompanied with the enlarging interfacial barrier height from 1 eV to 3.6 eV is observed no matter annealing the SiOx at short or long duration, as shown in Fig. 2. The existence of buried Si-QDs leads to a decreased turn-on voltage of the F-N tunneling and creates a tunneling path for carriers from Si substrate to ITO contact. A larger RF plasma power suppresses the Si-rich condition to shrink the Si-QDs in more stoichiomatric SiOx ilm, which provides a larger interfacial barrier height for carrier tunneling from ITO to SiOx.

For F-N tunneling, the calculated barrier height is effective barrier height at the interface between ITO gate and the whole SiOx:Si-QD film. Therefore, the effective barrier height is determined by the material characterization of SiOx film. Even though, the barrier height of SiOx/ITO junction is smaller than that of a pure SiO2/ITO junction (3.7 eV), indicating that the O/Si composition ratio is still below 2.0. The band diagrams of the MOSLEDs with Si-QDs embedded in the SiOx grown with different RF plasma powers are illustrated in Fig. 3, where the barrier height between ITO and SiOx grown with different RF plasma powers are depicted in the inset of Fig. 3. For example, the barrier heights of MOSLEDs with buried Si-QDs with sizes of 4.2 nm and 1.8 nm are 1.05 and 3.62 eV, respectively. It is straightforward that the band diagram bends more in smaller size of Si-QDs, indicating that a larger external electric field is needed to turn on the F-N tunneling mechanism in the MOSLEDs with smaller Si-QDs embedded in the SiOx. In our case, the O/Si composition ratio of the SiOx film enlarges with increasing RF plasma power. In addition, the excess Si concentration has a significant effect on the turn-on voltage of MOSLEDs [39

39. Z. H. Cen, T. P. Chen, L. Ding, Z. Liu, J. I. Wong, M. Yang, W. P. Goh, and S. Fung, “Influence of implantation dose on electroluminescence from Si-implanted silicon nitride thin films,” Appl. Phys., A Mater. Sci. Process. 104(1), 239–245 (2011). [CrossRef]

]. The less excess Si in the SiOx film provides fewer tunneling paths to make the current enhance. The SiOx film also enlarges its resistance with increasing O/Si composition ratio because the SiOx film gradually becomes non-stoichiometric to approach a pure SiO2 matrix. Therefore, the carriers need a higher turn-on voltage to be injected into Si-QDs. Moreover, the effective barrier height is varied with changing Si-QD size. That is because the smaller Si-QDs decrease the effective dielectric constant and enhance the barrier height of F-N tunneling to degrade overall tunneling probability [40

40. G. Chakraborty, S. Chattopadhyay, C. K. Sarkar, and C. Pramanik, “Tunneling current at the interface of silicon and silicon dioxide partly embedded with silicon nanocrystals in metal oxide semiconductor structures,” J. Appl. Phys. 101(2), 024315 (2007). [CrossRef]

].

Pavesi and Turan have simulated the individual states of the electron and hole energy levels with increasing Si-QD size. Their results have shown that the variation of conduction band is more than that of valence band for Si-QD size of smaller than 6 nm, and the quantum confinement effect of Si-QDs larger than 6 nm gradually diminishes [41

41. L. Pavesi and R. Turan, Silicon Nanocrystals: Fundamentals, Synthesis and Application (WILEY-VCH Verlag GmbH & Co. KGaA, 2010), Chap. 2, pp. 25.

]. These results clearly shown that the Fermi level in Si-QD moves upward with decreasing Si-QD size. The conduction band moves upward with shrinking Si-QD size, whereas the valence band moves downward with a smaller shift. Their simulation supports an upward movement of the Fermi level for smaller Si-QDs. Without bias, the larger bending degree of energy band at the Si-QD/SiO2 interface is observed for samples with smaller Si-QDs grown at higher RF plasma powers.

Alternatively, there is another simulation work attributing the increasing interfacial barrier height of Si-QDs with decreasing size to the down-shifted Fermi level, from which the difference between the Fermi level of Si-QDs and that of ITO decreases making the bending degree of the energy band less significant without external bias. The Fermi level would down-shift by shrinking Si-QD size because the asymmetrical shift of the conduction band and the valence band of Si-QDs. Due to the quantum confinement effect, the up-shift of the conduction band toward the vacuum band is less significant (actually, this shift can be ignored) than the down-shift of the valence band when decreasing the Si-QD size [42

42. T. Li, F. Gygi, and G. Galli, “Tailored nanoheterojunctions for optimized light emission,” Phys. Rev. Lett. 107(20), 206805 (2011). [CrossRef] [PubMed]

]. This results in an enlarged energy band (Eg) with down-shifted Fermi level for smaller Si-QDs, providing an enlarged interfacial barrier height by decreasing the Si-QD size. With the decrease of the size of Si-QDs by enlarging the RF power or lengthening the post annealing time, the Fermi level of Si-QDs down-shifts and the difference between the Fermi level of Si-QDs and that of ITO decreases making a less significant bending degree of energy band. Correspondingly, the effective barrier height ФB increases to assist carriers F-N tunneling from ITO to Si-QDs through SiO2 matrix. This inevitably induces the increased turn-on electrical fields (Eturn-on), as shown in Fig. 2.

Note that both models can successfully elucidate the decrease of the effective barrier height by enlarging Si-QD size and density results in a better carrier injection (it also depends on the resistance of the films). The overlap between electron and hole wave functions in both real and momentum space will increase in smaller Si-QDs with a higher probability of non-phonon assisted radiative recombination. Furthermore, the density of Si-QDs with smaller sizes is larger than that with larger sizes. Hence, the number of the active Si-QDs contributing to the luminescence is also increased as the size of Si-QDs reduces. The aforementioned mechanisms explain why a lower carrier injection as well as smaller current could lead to a larger external quantum efficiency and higher EL (see Fig. 5) observed from smaller Si-QDs even with a larger turn-on electrical field Eturn-on, as shown in Fig. 2.

In more detail, the EQE of the MOSLEDs grown with different RF plasma powers are plotted as a function of current density as shown in Fig. 5
Fig. 5 EQE (solid line) and EL power (dashed line) of MOSLEDs with 2.5-min (left) and 90-min (right) annealed SiOx samples grown at different RF plasma powers.
, which is defined as the ratio of the output photon number to the input electron number,
ηext=λ1λ2t0t1PEL(t,λ)I(t)ehνdtdλ=λ1λ2PEL(λ)λdλ1.24Ibias,
(2)
where PEL defines the optical output power, λ defines the peak wavelength, and Ibias defines the biased current. The maximal EQE of MOSLEDs with the 2.5-min annealed SiOx samples grown by enlarging RF plasma power from 20 to 50 W significantly increases from 1.9 × 10−5 to 2.4%. The MOSLEDs with SiOx films grown under RF power 50 W and after 2.5 min annealing demonstrate the best PCR and the highest EQE of 2.4% than ever. After annealing up to 90 min, the same devices slightly degrade its maximal EQE by one order of magnitude. For low RF power grown (20 and 30 W) MOSLEDs, the P-I slope, PCR and maximal EQE of long-term annealed devices are better than those of short-term annealed devices, but high RF power grown (40 and 50 W) devices show opposite results. The reason for such phenomenon is that the over-annealing contributes to the enlarged Si-QD size and the attenuated power at short wavelength region. There is a trade-off between the energy transforming efficiency and the operation reliability of these SiOx MOSLEDs with buried Si-QDs. The EQE of MOSLEDs has a slightly degraded phenomenon under the higher biasing current, as shown in Fig. 5. That is because the MOSLEDs under an operation of higher current injection easily contribute to a rise on device temperature. In addition, the impact ionization of hot carriers for devices easily occurs under an operation of the higher electric field [45

45. C.-J. Lin, C. K. Lee, E. W. G. Diau, and G.-R. Lin, “Time-resolved photoluminescence analysis of multidose Si-ion-implanted SiO2,” J. Electrochem. Soc. 153(2), E25–E32 (2006). [CrossRef]

]. The additional kinetic energy makes the electron-hole pairs separate from but not recombine with each other. Therefore, this phenomenon also contributes to the EQE degradation of MOSLEDs under the higher biasing current and electric field. In addition, the EQE of MOSLEDs also has a reduced phenomenon when the recombination mechanism is dominated by the defect or Auger recombination. The dominated recombination could be determined by the Z-parameter analysis [46

46. C.-H. Cheng, C.-L. Wu, C.-C. Chen, L.-H. Tsai, Y.-H. Lin, and G.-R. Lin, “Si-rich SixC1-x light-emitting diodes with buried Si quantum dots,” IEEE Photonics J. 4(5), 1762–1775 (2012). [CrossRef]

, 47

47. E. P. O’Reilly and M. Silver, “Temperature sensitivity and high temperature operation of long wavelength semiconductor lasers,” Appl. Phys. Lett. 63(24), 3318–3320 (1993). [CrossRef]

]. The Eq. (3) is based on the hypothesis of the Boltzmann statistics of carriers and an absence of leakage currents [48

48. L. L. Goddard, S. R. Bank, M. A. Wistey, H. B. Yuen, Z. Rao, and J. S. Harris Jr., “Recombination, gain, band structure, efficiency, and reliability of 1.5-µm GaInNAsSb/GaAs lasers,” J. Appl. Phys. 97(8), 083101 (2005). [CrossRef]

]. The Z-parameter could be obtained by the P-I curve of MOSLEDs, which is described as

Zln(I)ln(P0.5).
(3)

The annealing time dependent EL spectra blue-shifts with enlarging RF plasma power, as shown in Fig. 7
Fig. 7 EL spectra of MOSLEDs with SiOx grown at RF plasma powers of (a) 20 W, (b) 30 W, (c) 40 W and (d) 50 W under a biased current density of 0.1 mA/cm2.
. The biased current of MOSLEDs with SiOx films grown at larger RF plasma powers is decreased, because the O/Si composition ratio of the SiOx layer is increased dramatically to make the host matrix seriously isolated. The required turn-on current significantly reduces from 53.9 to 0.2 μA as the RF plasma power enlarges from 20 W to 50 W. In opposite, the EL intensity is enlarged by 40 times for the blue-light MOSLED even biases at smaller current. This is strongly correlated with the optical power-current slope discussed previously. For the MOSLED made by low-plasma grown SiOx with buried Si-QDs, two peak wavelengths of 480 and 681 nm are observed. After 90 min annealing, the latter peak has a red-shifted phenomenon due to the QCE. These two peaks compete and evolute each other as the biased current increases. The growth of SiOx films at higher RF plasma powers enables the precipitation of smaller Si-QDs in SiOx, which provides the EL color shifted from red to blue color even with short-term annealing. In particular, the long-term annealing makes Si atoms obtain more energies to diffuse a longer length to form larger Si-QDs, hence the corresponding EL spectrum slightly broadens toward long wavelengths and attenuates its EL intensity at shorter wavelengths accordingly.

The carrier transport and recombination through small Si-QDs are less efficient than those through large Si-QDs, because the less Si-rich SiOx host environment inevitably degrades the tunneling of carriers and the probability of tunneling through small Si-QDs is significantly reduced. With enlarging biased current, the EL contributed by larger Si-QDs gradually saturates and the overflowed carriers lead to the enhanced recombination in smaller Si-QD, as shown in Fig. 8
Fig. 8 Normalized EL spectra obtained under different biased currents for the MOSLED with SiOx film grown at an RF plasma power of 40 W. Inset: the EL intensity as a function of biased current.
. The inset of Fig. 8 depicts the linear relationship between the EL intensity and biasing currents. The output power as a function of biased currents can be written as PEL = ηext × Ibias × (1.24/λEL). For MOSLEDs with buried Si-QDs of different sizes, ηext and λEL are varied with the Si-QD sizes. The same phenomenon between EL intensity and biased voltages has been reported by Irrera et al [49

49. A. Irrera, D. Pacifici, M. Miritello, G. Franzo, F. Priolo, F. Iacona, F. Sanfilippo, G. Di Stefano, and P. G. Fallica, “Electroluminescence properties of light emitting devices based on silicon nanocrystals,” Phys. E 16(3-4), 395–399 (2003). [CrossRef]

]. The large-size Si-QD dependent EL grows and saturates earlier at lower biased condition, yet the EL power linearly increases before its saturation at higher biases.

The color of EL pattern shown in Fig. 9
Fig. 9 EL patterns (under a biased current density of 0.1 mA/cm2) of MOSLEDs with 2.5-min (upper) and 90-min (lower) annealed SiOx samples grown by changing RF plasma power from 20 to 50 W (from left to right).
varies from red to blue by increasing RF plasma powers during PECVD growth. Growing the SiOx at low RF power, the EL pattern is dark because of a low EL power for larger Si-QDs due to the greatly reduced wave-function overlap and recombination rate of electrons and holes. In contrast, the EL patterns become brighter with steeper P-I slope for MOSLEDs made on the SiOx prepared with lengthening annealing time. The long-term annealing provides brighter patterns due to the endurance of these MOSLEDs under higher current injection. The EL pattern of a 40-W grown SiOx based MOSLED reveals slightly green at lower bias but becomes a white-light pattern at higher current due to the EL spectral broadening and blue-shift effects. The brightest EL is observed from the MOSLEDs with smallest Si-QDs embedded in SiOx. The MOSLED with the 2.5-min annealed SiOx film shows a purely blue color but that with the 90-min annealed SiOx film varies to a light blue pattern due to the contribution of the slightly larger Si-QDs.

4. Conclusion

The carrier recombination rate and external quantum efficiency enhanced multicolor emission from SiOx based MOSLEDs with buried Si-QDs are demonstrated. With the RF plasma power increasing from 20 to 50 W during PECVD growth, the Si-rich condition is controlled to shrink the Si-QD size in non-stoichiomatric SiOx films and to provide a large interfacial barrier height for carrier confinement within small Si-QDs. The MOSLED made on a 2.5-min annealed SiOx film with buried Si-QDs slightly enlarges its maximal EL power from 7.5 to 75 nW. In contrast, the EL power significantly enlarges by one order of magnitude to 0.7 μW when the annealing time lengthens up to 90 min. The TRPL analysis reveals that the PL lifetime shortens from 5 µs to 0.31µs with shrinking the Si-QD size from 4.2 to 1.8 nm. This is attributed to a larger overlap between electron and hole wave functions, which essentially leads to a faster non-phonon-assisted direct carrier recombination in smaller Si-QDs. The turn-on currents of MOSLEDs after annealing for 2.5 and 90 min decrease from 53.9 to 0.2 μA and from 357.9 to 8.6 μA, respectively. The smaller Si-QD provides a deeper quantum well to enlarge the barrier height at ITO/SiOx interface, which leads to a better carrier confinement for carriers at cost of a less electron-hole wave-function overlap. The EQE of the Si-QD embedded in SiOx MOSLED grown with enlarging RF plasma powers significantly increases from 1.9 × 10−5 to 2.4% after annealing for 2.5 min. After annealing up to 90 min, the same devices slightly degrade the EQE by one order of magnitude but enlarge the EL power due to the enhanced carrier injection. The growth at higher plasma powers enables the precipitation of smaller Si-QDs in SiOx, which provides the EL color shifted from red to blue even with short-term annealing. In particular, the long-term annealing makes Si atoms obtain more energies to diffuse the longer length to form larger Si-QDs so that the EL spectrum slightly broadens toward long wavelengths and attenuates its EL intensity at shorter wavelengths accordingly. Such an all Si-based multicolor MOSLED with enhanced on IQE and EQE is fully compatible with current Si fabrication process, which could be used as an on-chip transmitter in the next-generation optical interconnect network to improve the chip-to-chip transmission performance.

Acknowledgment

This work was partially supported by the National Science Council, Taiwan, R.O.C. and the Excellent Research Projects of National Taiwan University, Taiwan, R.O.C., under grants NSC 100-2221-E-002-156-MY3, NSC 101-2622-E-002-009-CC2, NSC 101-ET-E-002-004-ET and 99R80301.

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G.-R. Lin, C.-J. Lin, C.-K. Lin, L.-J. Chou, and Y.-L. Chueh, “Oxygen defect and Si nanocrystal dependent white-light and near-infrared electroluminescence of Si-implanted and plasma-enhanced chemical-vapor deposition-grown Si-rich SiO2,” J. Appl. Phys. 97(9), 094306 (2005). [CrossRef]

9.

M. Wang, D. Yang, D. Li, Z. Yuan, and D. Que, “Correlation between luminescence and structural evolution of Si-rich silicon oxide film annealed at different temperatures,” J. Appl. Phys. 101(10), 103504 (2007). [CrossRef]

10.

D. Li, X. Zhang, L. Jin, and D. Yang, “Structure and luminescence evolution of annealed Europium-doped silicon oxides films,” Opt. Express 18(26), 27191–27196 (2010). [CrossRef] [PubMed]

11.

E. H. Snow, “Fowler-Nordheim tunneling in SiO2 films,” Solid State Commun. 5(10), 813–815 (1967). [CrossRef]

12.

M. Lenzlinger and E. H. Snow, “Fowler-Nordheim tunneling into thermally grown SiO2,” J. Appl. Phys. 40(1), 278–283 (1969). [CrossRef]

13.

Z. A. Weinberg, “On tunneling in metal-oxide-silicon structures,” J. Appl. Phys. 53(7), 5052–5056 (1982). [CrossRef]

14.

G. Chakraborty, S. Chattopadhyay, C. K. Sarkar, and C. Pramanik, “Tunneling current at the interface of silicon and silicon dioxide partly embedded with silicon nanocrystals in metal oxide semiconductor structures,” J. Appl. Phys. 101(2), 024315 (2007). [CrossRef]

15.

D. Comedi, O. H. Y. Zalloum, J. Wojcik, and P. Mascher, “Light emission from hydrogenated and unhydrogenated Si-nanocrystal/Si dioxide composites based on PECVD-grown Si-rich Si oxide films,” IEEE J. Sel. Top. Quantum Electron. 12(6), 1561–1569 (2006). [CrossRef]

16.

D. Comedi, O. H. Y. Zalloum, E. A. Irving, J. Wojcik, T. Roschuk, M. J. Flynn, and P. Mascher, “X-ray-diffraction study of crystalline Si nanocluster formation in annealed silicon-rich silicon oxides,” J. Appl. Phys. 99(2), 023518 (2006). [CrossRef]

17.

M. Wang, J. Huang, Z. Yuan, A. Anopchenko, D. Li, D. Yang, and L. Pavesi, “Light emission properties and mechanism of low-temperature prepared amorphous SiNx films. II. Defect states electroluminescence,” J. Appl. Phys. 104(8), 083505 (2008). [CrossRef]

18.

G.-R. Lin, Y.-H. Pai, C.-T. Lin, and C.-C. Chen, “Comparison on the electroluminescence of Si-rich SiNx and SiOx based light-emitting diodes,” Appl. Phys. Lett. 96(26), 263514 (2010). [CrossRef]

19.

F. Wang, D. Li, D. Yang, and D. Que, “Enhancement of light-extraction efficiency of SiNx light emitting devices through a rough Ag island film,” Appl. Phys. Lett. 100(3), 031113 (2012). [CrossRef]

20.

D. Li, F. Wang, D. Yang, and D. Que, “Electrically tunable electroluminescence from SiNx-based light-emitting devices,” Opt. Express 20(16), 17359–17366 (2012). [CrossRef] [PubMed]

21.

N. Lalic and J. Linnros, “Characterization of a porous silicon diode with efficient and tunable electroluminescence,” J. Appl. Phys. 80(10), 5971–5977 (1996). [CrossRef]

22.

A. Marconi, A. Anopchenko, M. Wang, G. Pucker, P. Bellutti, and L. Pavesi, “High power efficiency in Si-nc/SiO2 multilayer light emitting devices by bipolar direct tunneling,” Appl. Phys. Lett. 94(22), 221110 (2009). [CrossRef]

23.

G.-R. Lin, C.-J. Lin, and H.-C. Kuo, “Improving carrier transport and light emission in a silicon-nanocrystal based MOS light-emitting diode on silicon nanopillar array,” Appl. Phys. Lett. 91(9), 093122 (2007). [CrossRef]

24.

G.-R. Lin, C.-J. Lin, H.-C. Kuo, H.-S. Lin, and C.-C. Kuo, “Anomalous microphotoluminescence of high-aspect-ratio Si nanopillars formatted by dry-etching Si substrate with self-aggregated Ni nanodot mask,” Appl. Phys. Lett. 90(14), 143102 (2007). [CrossRef]

25.

K. Nishimura, Y. Nagao, and N. Ikeda, “High external quantum efficiency of electroluminescence from photoanodized porous silicon,” Jpn. J. Appl. Phys. 37(Part 2 No. 3B), L303–L305 (1998). [CrossRef]

26.

B. Gelloz and N. Koshida, “Electroluminescence with high and stable quantum efficiency and low threshold voltage from anodically oxidized thin porous silicon diode,” J. Appl. Phys. 88(7), 4319–4324 (2000). [CrossRef]

27.

A. Anopchenko, A. Marconi, M. Wang, G. Pucker, P. Bellutti, and L. Pavesi, “Graded-size Si quantum dot ensembles for efficient light-emitting diodes,” Appl. Phys. Lett. 99(18), 181108 (2011). [CrossRef]

28.

M. Perálvarez, J. Barreto, J. Carreras, A. Morales, D. Navarro-Urrios, Y. Lebour, C. Domínguez, and B. Garrido, “Si-nanocrystal-based LEDs fabricated by ion implantation and plasma-enhanced chemical vapour deposition,” Nanotechnology 20(40), 405201 (2009). [CrossRef] [PubMed]

29.

B.-H. Lai, C.-H. Cheng, and G.-R. Lin, “Multicolor ITO/SiOx/p-Si/Al light emitting diodes with improved emission efficiency by small Si quantum dots,” IEEE J. Quantum Electron. 47(5), 698–704 (2011). [CrossRef]

30.

G.-R. Lin, Y.-H. Pai, and C.-T. Lin, “Microwatt MOSLED using SiOx with buried Si nanocrystals on Si nano-pillar array,” J. Lightwave Technol. 26(11), 1486–1491 (2008). [CrossRef]

31.

Y.-C. Lien, Y.-H. Pai, and G.-R. Lin, “Si nano-dots and nano-pyramids dependent light emission and charge accumulation in ITO/SiOx/p-Si MOS diode,” IEEE J. Quantum Electron. 46(1), 121–127 (2010). [CrossRef]

32.

E. Sun, F.-H. Su, Y.-T. Shih, H.-L. Tsai, C.-H. Chen, M.-K. Wu, J.-R. Yang, and M.-J. Chen, “An efficient Si light-emitting diode based on an n-ZnO/SiO2-Si nanocrystals-SiO2/p-Si heterostructure,” Nanotechnology 20(44), 445202 (2009). [CrossRef] [PubMed]

33.

K.-Y. Cheng, R. Anthony, U. R. Kortshagen, and R. J. Holmes, “High-efficiency silicon nanocrystal light-emitting devices,” Nano Lett. 11(5), 1952–1956 (2011). [CrossRef] [PubMed]

34.

D. P. Puzzo, E. J. Henderson, M. G. Helander, Z. B. Wang, G. A. Ozin, and Z. Lu, “Visible colloidal nanocrystal silicon light-emitting diode,” Nano Lett. 11(4), 1585–1590 (2011). [CrossRef] [PubMed]

35.

B.-H. Lai, C.-H. Cheng, Y.-H. Pai, and G.-R. Lin, “Plasma power controlled deposition of SiOx with manipulated Si Quantum Dot size for photoluminescent wavelength tailoring,” Opt. Express 18(5), 4449–4456 (2010). [CrossRef] [PubMed]

36.

W.-L. Hsu, Y.-H. Pai, F.-S. Meng, C.-W. Liu, and G.-R. Lin, “Nanograin crystalline transformation enhanced UV transparency of annealing refined indium tin oxide film,” Appl. Phys. Lett. 94(23), 231906 (2009). [CrossRef]

37.

C.-D. Lin, C.-H. Cheng, Y.-H. Lin, C.-L. Wu, Y.-H. Pai, and G.-R. Lin, “Comparing retention and recombination of electrically injected carriers in Si quantum dots embedded in Si-rich SiNx films,” Appl. Phys. Lett. 99(24), 243501 (2011). [CrossRef]

38.

R. H. Fowler and L. Nordheim, “Electron emission in intense electric fields,” Proc. R. Soc. Lond., A Contain. Pap. Math. Phys. Character 119(781), 173–181 (1928). [CrossRef]

39.

Z. H. Cen, T. P. Chen, L. Ding, Z. Liu, J. I. Wong, M. Yang, W. P. Goh, and S. Fung, “Influence of implantation dose on electroluminescence from Si-implanted silicon nitride thin films,” Appl. Phys., A Mater. Sci. Process. 104(1), 239–245 (2011). [CrossRef]

40.

G. Chakraborty, S. Chattopadhyay, C. K. Sarkar, and C. Pramanik, “Tunneling current at the interface of silicon and silicon dioxide partly embedded with silicon nanocrystals in metal oxide semiconductor structures,” J. Appl. Phys. 101(2), 024315 (2007). [CrossRef]

41.

L. Pavesi and R. Turan, Silicon Nanocrystals: Fundamentals, Synthesis and Application (WILEY-VCH Verlag GmbH & Co. KGaA, 2010), Chap. 2, pp. 25.

42.

T. Li, F. Gygi, and G. Galli, “Tailored nanoheterojunctions for optimized light emission,” Phys. Rev. Lett. 107(20), 206805 (2011). [CrossRef] [PubMed]

43.

G.-R. Lin, C.-J. Lin, and K.-C. Yu, “Time-resolved photoluminescence and capacitance-voltage analysis of the neutral vacancy defect in silicon implanted SiO2 on silicon substrate,” J. Appl. Phys. 96(5), 3025–3027 (2004). [CrossRef]

44.

V. A. Belyakov, V. A. Burdov, R. Lockwood, and A. Merdrum, “Silicon nanocrystals: fundamental theory and implications for stimulated emission,” Advances in Optical Technologies, review article ID 279502 (2008).

45.

C.-J. Lin, C. K. Lee, E. W. G. Diau, and G.-R. Lin, “Time-resolved photoluminescence analysis of multidose Si-ion-implanted SiO2,” J. Electrochem. Soc. 153(2), E25–E32 (2006). [CrossRef]

46.

C.-H. Cheng, C.-L. Wu, C.-C. Chen, L.-H. Tsai, Y.-H. Lin, and G.-R. Lin, “Si-rich SixC1-x light-emitting diodes with buried Si quantum dots,” IEEE Photonics J. 4(5), 1762–1775 (2012). [CrossRef]

47.

E. P. O’Reilly and M. Silver, “Temperature sensitivity and high temperature operation of long wavelength semiconductor lasers,” Appl. Phys. Lett. 63(24), 3318–3320 (1993). [CrossRef]

48.

L. L. Goddard, S. R. Bank, M. A. Wistey, H. B. Yuen, Z. Rao, and J. S. Harris Jr., “Recombination, gain, band structure, efficiency, and reliability of 1.5-µm GaInNAsSb/GaAs lasers,” J. Appl. Phys. 97(8), 083101 (2005). [CrossRef]

49.

A. Irrera, D. Pacifici, M. Miritello, G. Franzo, F. Priolo, F. Iacona, F. Sanfilippo, G. Di Stefano, and P. G. Fallica, “Electroluminescence properties of light emitting devices based on silicon nanocrystals,” Phys. E 16(3-4), 395–399 (2003). [CrossRef]

OCIS Codes
(160.2540) Materials : Fluorescent and luminescent materials
(230.3670) Optical devices : Light-emitting diodes
(310.1860) Thin films : Deposition and fabrication
(160.4236) Materials : Nanomaterials

ToC Category:
Materials

History
Original Manuscript: September 11, 2012
Revised Manuscript: November 10, 2012
Manuscript Accepted: November 13, 2012
Published: January 4, 2013

Citation
Chih-Hsien Cheng, Yu-Chung Lien, Chung-Lun Wu, and Gong-Ru Lin, "Mutlicolor electroluminescent Si quantum dots embedded in SiOx thin film MOSLED with 2.4% external quantum efficiency," Opt. Express 21, 391-403 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-1-391


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References

  1. F. Koch, V. Petrova-Koch, and T. Muschik, “The luminescence of porous Si: the case for the surface state mechanism,” J. Lumin.57(1-6), 271–281 (1993). [CrossRef]
  2. S. M. Prokes, “Light emission in thermally oxidized porous silicon: Evidence for oxide-related luminescence,” Appl. Phys. Lett.62(25), 3244–3246 (1993). [CrossRef]
  3. B. Delley and E. F. Steigmeier, “Quantum confinement in Si nanocrystals,” Phys. Rev. B Condens. Matter47(3), 1397–1400 (1993). [CrossRef] [PubMed]
  4. N.-M. Park, C.-J. Choi, T.-Y. Seong, and S.-J. Park, “Quantum Confinement in Amorphous Silicon Quantum Dots Embedded in Silicon Nitride,” Phys. Rev. Lett.86(7), 1355–1357 (2001). [CrossRef] [PubMed]
  5. P. D. Nguyen, D. M. Kepaptsoglou, Q. M. Ramasse, and A. Olsen, “Direct observation of quantum confinement of Si nanocrystals in Si-rich nitrides,” Phys. Rev. B85(8), 085315 (2012). [CrossRef]
  6. W. D. A. M. de Boer, D. Timmerman, K. Dohnalová, I. N. Yassievich, H. Zhang, W. J. Buma, and T. Gregorkiewicz, “Red spectral shift and enhanced quantum efficiency in phonon-free photoluminescence from silicon nanocrystals,” Nat. Nanotechnol.5(12), 878–884 (2010). [CrossRef] [PubMed]
  7. J. Linnros and N. Lalic, “High quantum efficiency for a porous silicon light emitting diode under pulsed operation,” Appl. Phys. Lett.66(22), 3048–3050 (1995). [CrossRef]
  8. G.-R. Lin, C.-J. Lin, C.-K. Lin, L.-J. Chou, and Y.-L. Chueh, “Oxygen defect and Si nanocrystal dependent white-light and near-infrared electroluminescence of Si-implanted and plasma-enhanced chemical-vapor deposition-grown Si-rich SiO2,” J. Appl. Phys.97(9), 094306 (2005). [CrossRef]
  9. M. Wang, D. Yang, D. Li, Z. Yuan, and D. Que, “Correlation between luminescence and structural evolution of Si-rich silicon oxide film annealed at different temperatures,” J. Appl. Phys.101(10), 103504 (2007). [CrossRef]
  10. D. Li, X. Zhang, L. Jin, and D. Yang, “Structure and luminescence evolution of annealed Europium-doped silicon oxides films,” Opt. Express18(26), 27191–27196 (2010). [CrossRef] [PubMed]
  11. E. H. Snow, “Fowler-Nordheim tunneling in SiO2 films,” Solid State Commun.5(10), 813–815 (1967). [CrossRef]
  12. M. Lenzlinger and E. H. Snow, “Fowler-Nordheim tunneling into thermally grown SiO2,” J. Appl. Phys.40(1), 278–283 (1969). [CrossRef]
  13. Z. A. Weinberg, “On tunneling in metal-oxide-silicon structures,” J. Appl. Phys.53(7), 5052–5056 (1982). [CrossRef]
  14. G. Chakraborty, S. Chattopadhyay, C. K. Sarkar, and C. Pramanik, “Tunneling current at the interface of silicon and silicon dioxide partly embedded with silicon nanocrystals in metal oxide semiconductor structures,” J. Appl. Phys.101(2), 024315 (2007). [CrossRef]
  15. D. Comedi, O. H. Y. Zalloum, J. Wojcik, and P. Mascher, “Light emission from hydrogenated and unhydrogenated Si-nanocrystal/Si dioxide composites based on PECVD-grown Si-rich Si oxide films,” IEEE J. Sel. Top. Quantum Electron.12(6), 1561–1569 (2006). [CrossRef]
  16. D. Comedi, O. H. Y. Zalloum, E. A. Irving, J. Wojcik, T. Roschuk, M. J. Flynn, and P. Mascher, “X-ray-diffraction study of crystalline Si nanocluster formation in annealed silicon-rich silicon oxides,” J. Appl. Phys.99(2), 023518 (2006). [CrossRef]
  17. M. Wang, J. Huang, Z. Yuan, A. Anopchenko, D. Li, D. Yang, and L. Pavesi, “Light emission properties and mechanism of low-temperature prepared amorphous SiNx films. II. Defect states electroluminescence,” J. Appl. Phys.104(8), 083505 (2008). [CrossRef]
  18. G.-R. Lin, Y.-H. Pai, C.-T. Lin, and C.-C. Chen, “Comparison on the electroluminescence of Si-rich SiNx and SiOx based light-emitting diodes,” Appl. Phys. Lett.96(26), 263514 (2010). [CrossRef]
  19. F. Wang, D. Li, D. Yang, and D. Que, “Enhancement of light-extraction efficiency of SiNx light emitting devices through a rough Ag island film,” Appl. Phys. Lett.100(3), 031113 (2012). [CrossRef]
  20. D. Li, F. Wang, D. Yang, and D. Que, “Electrically tunable electroluminescence from SiNx-based light-emitting devices,” Opt. Express20(16), 17359–17366 (2012). [CrossRef] [PubMed]
  21. N. Lalic and J. Linnros, “Characterization of a porous silicon diode with efficient and tunable electroluminescence,” J. Appl. Phys.80(10), 5971–5977 (1996). [CrossRef]
  22. A. Marconi, A. Anopchenko, M. Wang, G. Pucker, P. Bellutti, and L. Pavesi, “High power efficiency in Si-nc/SiO2 multilayer light emitting devices by bipolar direct tunneling,” Appl. Phys. Lett.94(22), 221110 (2009). [CrossRef]
  23. G.-R. Lin, C.-J. Lin, and H.-C. Kuo, “Improving carrier transport and light emission in a silicon-nanocrystal based MOS light-emitting diode on silicon nanopillar array,” Appl. Phys. Lett.91(9), 093122 (2007). [CrossRef]
  24. G.-R. Lin, C.-J. Lin, H.-C. Kuo, H.-S. Lin, and C.-C. Kuo, “Anomalous microphotoluminescence of high-aspect-ratio Si nanopillars formatted by dry-etching Si substrate with self-aggregated Ni nanodot mask,” Appl. Phys. Lett.90(14), 143102 (2007). [CrossRef]
  25. K. Nishimura, Y. Nagao, and N. Ikeda, “High external quantum efficiency of electroluminescence from photoanodized porous silicon,” Jpn. J. Appl. Phys.37(Part 2 No. 3B), L303–L305 (1998). [CrossRef]
  26. B. Gelloz and N. Koshida, “Electroluminescence with high and stable quantum efficiency and low threshold voltage from anodically oxidized thin porous silicon diode,” J. Appl. Phys.88(7), 4319–4324 (2000). [CrossRef]
  27. A. Anopchenko, A. Marconi, M. Wang, G. Pucker, P. Bellutti, and L. Pavesi, “Graded-size Si quantum dot ensembles for efficient light-emitting diodes,” Appl. Phys. Lett.99(18), 181108 (2011). [CrossRef]
  28. M. Perálvarez, J. Barreto, J. Carreras, A. Morales, D. Navarro-Urrios, Y. Lebour, C. Domínguez, and B. Garrido, “Si-nanocrystal-based LEDs fabricated by ion implantation and plasma-enhanced chemical vapour deposition,” Nanotechnology20(40), 405201 (2009). [CrossRef] [PubMed]
  29. B.-H. Lai, C.-H. Cheng, and G.-R. Lin, “Multicolor ITO/SiOx/p-Si/Al light emitting diodes with improved emission efficiency by small Si quantum dots,” IEEE J. Quantum Electron.47(5), 698–704 (2011). [CrossRef]
  30. G.-R. Lin, Y.-H. Pai, and C.-T. Lin, “Microwatt MOSLED using SiOx with buried Si nanocrystals on Si nano-pillar array,” J. Lightwave Technol.26(11), 1486–1491 (2008). [CrossRef]
  31. Y.-C. Lien, Y.-H. Pai, and G.-R. Lin, “Si nano-dots and nano-pyramids dependent light emission and charge accumulation in ITO/SiOx/p-Si MOS diode,” IEEE J. Quantum Electron.46(1), 121–127 (2010). [CrossRef]
  32. E. Sun, F.-H. Su, Y.-T. Shih, H.-L. Tsai, C.-H. Chen, M.-K. Wu, J.-R. Yang, and M.-J. Chen, “An efficient Si light-emitting diode based on an n-ZnO/SiO2-Si nanocrystals-SiO2/p-Si heterostructure,” Nanotechnology20(44), 445202 (2009). [CrossRef] [PubMed]
  33. K.-Y. Cheng, R. Anthony, U. R. Kortshagen, and R. J. Holmes, “High-efficiency silicon nanocrystal light-emitting devices,” Nano Lett.11(5), 1952–1956 (2011). [CrossRef] [PubMed]
  34. D. P. Puzzo, E. J. Henderson, M. G. Helander, Z. B. Wang, G. A. Ozin, and Z. Lu, “Visible colloidal nanocrystal silicon light-emitting diode,” Nano Lett.11(4), 1585–1590 (2011). [CrossRef] [PubMed]
  35. B.-H. Lai, C.-H. Cheng, Y.-H. Pai, and G.-R. Lin, “Plasma power controlled deposition of SiOx with manipulated Si Quantum Dot size for photoluminescent wavelength tailoring,” Opt. Express18(5), 4449–4456 (2010). [CrossRef] [PubMed]
  36. W.-L. Hsu, Y.-H. Pai, F.-S. Meng, C.-W. Liu, and G.-R. Lin, “Nanograin crystalline transformation enhanced UV transparency of annealing refined indium tin oxide film,” Appl. Phys. Lett.94(23), 231906 (2009). [CrossRef]
  37. C.-D. Lin, C.-H. Cheng, Y.-H. Lin, C.-L. Wu, Y.-H. Pai, and G.-R. Lin, “Comparing retention and recombination of electrically injected carriers in Si quantum dots embedded in Si-rich SiNx films,” Appl. Phys. Lett.99(24), 243501 (2011). [CrossRef]
  38. R. H. Fowler and L. Nordheim, “Electron emission in intense electric fields,” Proc. R. Soc. Lond., A Contain. Pap. Math. Phys. Character119(781), 173–181 (1928). [CrossRef]
  39. Z. H. Cen, T. P. Chen, L. Ding, Z. Liu, J. I. Wong, M. Yang, W. P. Goh, and S. Fung, “Influence of implantation dose on electroluminescence from Si-implanted silicon nitride thin films,” Appl. Phys., A Mater. Sci. Process.104(1), 239–245 (2011). [CrossRef]
  40. G. Chakraborty, S. Chattopadhyay, C. K. Sarkar, and C. Pramanik, “Tunneling current at the interface of silicon and silicon dioxide partly embedded with silicon nanocrystals in metal oxide semiconductor structures,” J. Appl. Phys.101(2), 024315 (2007). [CrossRef]
  41. L. Pavesi and R. Turan, Silicon Nanocrystals: Fundamentals, Synthesis and Application (WILEY-VCH Verlag GmbH & Co. KGaA, 2010), Chap. 2, pp. 25.
  42. T. Li, F. Gygi, and G. Galli, “Tailored nanoheterojunctions for optimized light emission,” Phys. Rev. Lett.107(20), 206805 (2011). [CrossRef] [PubMed]
  43. G.-R. Lin, C.-J. Lin, and K.-C. Yu, “Time-resolved photoluminescence and capacitance-voltage analysis of the neutral vacancy defect in silicon implanted SiO2 on silicon substrate,” J. Appl. Phys.96(5), 3025–3027 (2004). [CrossRef]
  44. V. A. Belyakov, V. A. Burdov, R. Lockwood, and A. Merdrum, “Silicon nanocrystals: fundamental theory and implications for stimulated emission,” Advances in Optical Technologies, review article ID 279502 (2008).
  45. C.-J. Lin, C. K. Lee, E. W. G. Diau, and G.-R. Lin, “Time-resolved photoluminescence analysis of multidose Si-ion-implanted SiO2,” J. Electrochem. Soc.153(2), E25–E32 (2006). [CrossRef]
  46. C.-H. Cheng, C.-L. Wu, C.-C. Chen, L.-H. Tsai, Y.-H. Lin, and G.-R. Lin, “Si-rich SixC1-x light-emitting diodes with buried Si quantum dots,” IEEE Photonics J.4(5), 1762–1775 (2012). [CrossRef]
  47. E. P. O’Reilly and M. Silver, “Temperature sensitivity and high temperature operation of long wavelength semiconductor lasers,” Appl. Phys. Lett.63(24), 3318–3320 (1993). [CrossRef]
  48. L. L. Goddard, S. R. Bank, M. A. Wistey, H. B. Yuen, Z. Rao, and J. S. Harris., “Recombination, gain, band structure, efficiency, and reliability of 1.5-µm GaInNAsSb/GaAs lasers,” J. Appl. Phys.97(8), 083101 (2005). [CrossRef]
  49. A. Irrera, D. Pacifici, M. Miritello, G. Franzo, F. Priolo, F. Iacona, F. Sanfilippo, G. Di Stefano, and P. G. Fallica, “Electroluminescence properties of light emitting devices based on silicon nanocrystals,” Phys. E16(3-4), 395–399 (2003). [CrossRef]

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