- Nano Express
- Open Access
Direct Growth of III-Nitride Nanowire-Based Yellow Light-Emitting Diode on Amorphous Quartz Using Thin Ti Interlayer
© The Author(s) 2018
- Received: 10 December 2017
- Accepted: 23 January 2018
- Published: 6 February 2018
Consumer electronics have increasingly relied on ultra-thin glass screen due to its transparency, scalability, and cost. In particular, display technology relies on integrating light-emitting diodes with display panel as a source for backlighting. In this study, we undertook the challenge of integrating light emitters onto amorphous quartz by demonstrating the direct growth and fabrication of a III-nitride nanowire-based light-emitting diode. The proof-of-concept device exhibits a low turn-on voltage of 2.6 V, on an amorphous quartz substrate. We achieved ~ 40% transparency across the visible wavelength while maintaining electrical conductivity by employing a TiN/Ti interlayer on quartz as a translucent conducting layer. The nanowire-on-quartz LED emits a broad linewidth spectrum of light centered at true yellow color (~ 590 nm), an important wavelength bridging the green-gap in solid-state lighting technology, with significantly less strain and dislocations compared to conventional planar quantum well nitride structures. Our endeavor highlighted the feasibility of fabricating III-nitride optoelectronic device on a scalable amorphous substrate through facile growth and fabrication steps. For practical demonstration, we demonstrated tunable correlated color temperature white light, leveraging on the broadly tunable nanowire spectral characteristics across red-amber-yellow color regime.
- True yellow
- Gallium nitride
- Amorphous quartz
- Light-emitting diodes
The use of light-emitting diode (LED) for display technology has become widespread over the past decade. These light sources are more energy efficient compared to cold cathode fluorescent lamp (CCFL) and more suitable for portable consumer electronics. Conventional LEDs rely on GaN-based blue LEDs grown on sapphire substrates. As the demand for LED products increases, the trend is shifting towards the use of larger diameter sapphire substrate to scale up manufacturing yield. However, the large-size sapphire substrate is challenging to manufacture due to difficulties in precise drilling of c-plane sapphire from Kyropoulos boules while maintaining accurate crystal orientation and flatness with increasing diameter [1, 2]. In addition to manufacturing issues, conventional planar GaN-based LEDs are constrained by the existence of the green-gap, i.e., the spectral region where the LED quantum efficiency decreases for wavelengths longer than the green wavelength (520 nm).
There have been several attempts to grow III-nitride materials atop glass-based substrates. Previously, epitaxial growth of GaN on glass using gas-source molecular beam epitaxy (MBE)  and sputtering [4, 5] have produced low-quality polycrystalline material, affecting device performance. Alternatively, Samsung has demonstrated the capability of growing nearly single-crystalline GaN pyramids on glass by micromasking and subsequent selective metal organic chemical vapor deposition (MOCVD) growth [6, 7]. However, the excessive indium evaporation in MOCVD prevents efficient incorporation of indium for achieving emitters in the green-gap. Shon et al. demonstrated the possibility of improving the quality of a sputtered InGaN thin film on amorphous glass using graphene as a pre-orienting buffer layer, effectively suppressing the defect-related photoluminescence . Nevertheless, these methods require complex processing steps that hinder the potential for integration into large-scale manufacturing processes.
One possible method of directly incorporating III-nitride light emitter with glass-based substrate is by utilizing spontaneously grown III-nitride nanowires using MBE. By optimizing the growth condition, it is possible to have III-nitride nanowires grow spontaneously without the need for any templated growth-mask or catalyst . Because of the large surface to volume ratio, the nanowires can grow free of threading dislocation  while having reduced strain in the active region. The reduced strain enables fabrication of III-nitride nanowire-based devices working within the green-gap and beyond [11–16]. The III-nitride nanowires have been shown to grow on various substrates, such as silicon [9, 17, 18], metal [19–21], and silica [22–25], making it possible to utilize a broad range of substrates. Currently, due to the insulating nature of the glass-based substrate, it is challenging to fabricate an electrically injected device atop silica while maintaining both conductivity and transparency simultaneously.
In this work, we undertook this challenge, and successfully demonstrate the growth and fabrication of an InGaN/GaN nanowire-based LED grown on an amorphous quartz substrate. We achieved simultaneous transparency and conductivity by employing a translucent TiN/Ti interlayer as the conductive layer and the growth site for the nanowires. Because the nanowires grow spontaneously without a requisite global epitaxial relationship with the substrate, no complex or expensive processing steps are required before material growth. The nanowires-on-quartz LED emits a broad linewidth yellow light centered at ~ 590 nm, a color that is challenging to achieve with conventional planar quantum-well nitride technologies, thus further accentuate the significance of our current work.
For a practical demonstration, we have also performed correlated color temperature (CCT) tuning experiment based on mixed spontaneous and stimulated light sources. The use of transparent amorphous quartz allows the direct transmission of light from a laser diode for white light generation. Growing nanowires on quartz opens up new possibilities and opportunities for realizing integrated light emitters operating in the green-gap while benefiting from the scalability of amorphous quartz technology. Despite the technological infancy as compared to planar group III-nitride LEDs, the unique properties of nitrided titanium for nanowire growth is paramount to enabling seamless integration of light emitter on transparent substrate.
The nanowires-on-quartz samples were grown catalyst-free under nitrogen-rich condition using a Veeco GEN 930 PA-MBE system. A commercial double polished amorphous quartz substrate (thickness ~ 500 μ m) is first cleaned using acetone and isopropyl alcohol rinse and dried using nitrogen blow-dry. Before growth, 20-nm thick Ti layer was deposited using electron beam evaporation to act as the translucent conducting interlayer. After Ti deposition, another round of solvent cleaning using acetone and isopropyl alcohol is performed. Two rounds of outgassing were performed to remove any moisture and contaminants from the substrate surface. After loading into the growth chamber, the substrate surface is exposed to a nitrogen plasma to partially convert the Ti into TiN before opening the Ga shutter. The nitrogen was kept at 1-sccm flow rate and 350-W RF power during nitridation and throughout the growth process. For n-type GaN:Si nanowire base growth, the Ga beam equivalent pressure (BEP) was 6.5 × 10−8 Torr while Si cell temperature was kept at 1165 °C. We utilized a two-step growth method to obtain high-quality GaN while controlling the density of the nanowires. The GaN nanowire nucleation layer was deposited at a substrate temperature of 620 °C for 10 min, followed by GaN nanowire growth at an elevated temperature (770 °C). After n-GaN growth, the active region consisting of five pairs of InGaN quantum disks and GaN quantum barriers were deposited. In BEP was 5 × 10−8 Torr, and Ga was 3 × 10−8 Torr for quantum disk growth. A p-type GaN:Mg section was grown after the final GaN quantum barrier. The Mg cell was kept at 310 °C during p-GaN growth.
Optical and Structural Characterization
The photoluminescence (PL) characteristics of the nanowires grown on quartz was measured using temperature-dependent μ-PL measurements using a 325-nm HeCd laser as the excitation source and × 15 UV objective lens. The output power of the laser is ~ 3.74 mW. The beam spot size is ~ 1.24 μm, which gives a corresponding excitation power density of ~ 310 kW/cm2. The sample was cooled to liquid nitrogen temperature using a cryostat cell (Linkam, THMS 6000). The temperature is then adjusted from 77 to 300 K. Sample transparency was measured using a Shimadzu UV-3600 UV-vis-NIR spectrophotometer. Calibration was performed using air as the reference. SEM images were taken using FEI quanta 600. High-resolution transmission electron microscopy (HRTEM) and high-resolution high-angle annular dark field STEM (HAADF-STEM) characterizations were carried out using a Titan 80-300 ST transmission electron microscope (FEI Company) operated at an accelerating voltage of 300 kV. The elemental composition map were obtained via energy dispersive X-ray spectroscopy (EDS) from EDAX Company.
Device Fabrication and Characterization
The device fabrication is as follows. First, the as-grown nanowire sample is cleaned through standard solvent cleaning using acetone and isopropyl alcohol followed by nitrogen blow dry. Next, ~ 2 μ m of parylene C is deposited through thermal evaporation. An etch-back process using oxygen plasma reactive ion etching (RIE) is performed to expose the p-type nanowire tips. Afterwards, 5 nm of Ni is deposited using electron-beam evaporation followed by 230 nm of indium tin oxide (ITO) deposited using RF magnetron sputtering as the transparent current spreading layer. Annealing is done at 500 °C under Ar ambient to improve the electrical characteristics of the Ni/ITO transparent current spreading layer. Inductively coupled plasma (ICP) RIE etching is done using Cl- and Ar-based ions to define device mesa. Finally, a Ni/Au contact pad is deposited through electron-beam evaporation followed by lift-off. L-I-V characterization was performed using a Keithley 2400 power meter. Thermal measurement and imaging was conducted using a commercial Optotherm micro radiometric thermal imaging microscope. Prior to actual temperature measurement, a 2D emissivity mapping table is constructed for each pixel of the image in order to take into account the different surface emissivity values caused by different material components. This is done by heating the device to 60 °C using a heating stage and constructing the table using the Thermalyze thermal image analysis software provided by the system. After the table is constructed, the heating stage is switched off and current-dependent measurement is performed.
Structural and Optical Characterization of Nanowires Grown on Quartz
High-resolution bright field transmission electron microscope (TEM) image of the nanowire is shown in Fig. 1b, along with the corresponding selective area diffraction pattern shown in the inset. The diffraction pattern is an indication of the crystallinity of the nanowire, showing the growth high-quality GaN material on a lattice-mismatched substrate. High-angle annular dark field (HAADF) image of a single nanowire along with the corresponding elemental mapping is shown in Fig. 1c–f. The HAADF image shows five InGaN quantum disk (qdisk) insertions as the active region, indicated by brighter spots in the nanowire. At the base of the nanowire, a debris-like layer can be seen. This layer is the remains of the initial GaN nanowire seed that does not grow into nanowire due to shadowing effect. Elemental mapping shows that the nanowires grow on top of the Ti interlayer and not directly on top of the quartz substrate.
The TEM elemental mapping on the interface between the nanowire, interlayer, and quartz substrate is also shown in Fig. 1g–h to give a better understanding of the composition of the interface. Elemental mapping for Ga, Ti, and Si was performed using energy-dispersive X-ray analysis (EDX) while elemental mapping for O and N was performed using electron energy loss spectroscopy (EELS). Elemental mapping performed at the interface confirms that the top part of the Ti layer was partially converted into TiN during growth inside the MBE chamber, as indicated by the simultaneous presence of Ti and N on top of the interlayer. The TiN layer is estimated to be ~ 10 nm thick. The GaN seed nucleation and nanowire growth then occur on top of the TiN layer. EELS result shows the existence of oxygen signal across the TiN/Ti layer. This is caused by the spontaneous formation of native TiO2 film as the TEM sample is exposed to air after preparation . The direct nucleation on TiN is advantageous for our device design, as TiN is shown to be capable of simultaneous transparency and conductivity  while also improving the quality of GaN grown on top of it  and acting as a reflector on longer wavelength .
Figure 5 shows the electrical characterization results of the a 500 μm×500 μm-sized nanowire-on-quartz device. The turn-on voltage, by linear extrapolation of the linear region of the V-I curve, was determined to be ~ 2.6 V. The turn-on resistance (~ 300 Ω) is higher than that of nanowire-based LED devices fabricated on silicon and metal platform primarily because of the limited conductivity of the thin TiN/Ti layer in combination with the spontaneous formation of insulating TiO2 layer . When device transparency is non-critical, the turn-on resistance can be improved by depositing a thicker Ti interlayer before growth. The light output power shown in the result of the L-I measurement is relatively low, as only light emitted normal to the device plane is collected. The light emission from the device in Fig. 5b shows that part of the light emitted by the device couples into the surrounding quartz substrate area and is partially backscattered normal to the substrate plane, resulting in low light extraction efficiency. However, this result also highlights the possibility of using the nanowire-on-quartz LED as the foundation for an all-optical circuit on a glass platform by carefully engineering the coupling and guiding of photons inside the quartz substrate.
Electroluminescence (EL) measurement results in Fig. 5d, e show a broad emission linewidth of above 120 nm. The electroluminescence peak agrees well with the room temperature μ-PL measurement. At a low injection current density approximately at turn-on, the LED exhibits a broad spectral emission near the red wavelength. With increasing injection current, the spectrum blue-shifts from 650 nm towards 590 nm thus realizing on-chip tuning across red-amber-yellow color regime. The blue-shift in peak wavelength is related to progressive band filling effect where at a high injection current electron starts filling higher energy state and recombine, resulting in emission at shorter peak wavelength. At higher injection current, the blue-shifting of the peak wavelength is saturated, due to competition between blue-shifting and red-shifting caused by the increase in junction temperature. Using a quantum-disk-in-nanowire structure, the polarization field is reduced through strain relief, thus enabling the realization of a yellow LED device which is challenging to achieve with a planar quantum well-based device.
Color Mixing Experiment
A CCT-tunable high-quality white light source plays an important role in consumer electronics, as it has been shown that the blue light component on the electronic display leads to suppression of melatonin, effectively interfering with human circadian rhythm [38, 39]. Capitalizing on the broadly tunable spectral characteristics of the device, we demonstrated a practical application of a widely CCT-tunable white light generation in a transmission configuration. We used the nanowire-on-quartz LED as the active widely tunable element with the red, green, and blue (RGB) laser diodes (LDs) as the secondary light sources. One advantage of using nanowire-based yellow light source for generating white light is the inherent broad emission, which leads to high color rendering index (CRI) value. By utilizing the yellow LED in conjunction with lasers, we were able to design a widely CCT-tunable white light. The arrangement of the color mixing setup is described as follows.
In the first experiment, the beam from a blue LD was combined with the yellow light from the yellow LED. To obtain the highest CRI value possible, the bias currents of the LD and LED were initially varied, yielding a CRI value of 74.5 with a CCT value of 6769 K. This value is much higher than our previous result using a blue LD/YAG:Ce 3+ phosphor for white light generation . To demonstrate the color tunability, either the LED or the LD bias was varied, starting from the bias value that produced the highest CRI. Figure 7b, c shows the effect of adjusting the bias current on the CRI and CCT values. We were able to tune the color temperature from 2800 K to over 7000 K while maintaining a CRI value above 55. Figure 7d shows the spectrum from the highest CRI achieved, with the inset showing the change in the CIE 1931 coordinate by varying the bias current. Further improvement to the CRI value was made using RGB LDs in conjunction with the yellow LED. When only the RGB LDs are utilized without the yellow LED spectrum component, we obtained a CRI value of 55.4. By incorporating the yellow spectrum component, we were able to obtain a high-quality white light with a CCT value of 7300 K and a CRI value of 85.1 (Fig. 7e), which is significantly higher.
By utilizing the nanowire-on-quartz LED in conjunction with laser diode system, we are able to design a widely CCT-tunable white light source while avoiding the issue of phosphor degradation . By controlling the spectral characteristics of each wavelength individually, fine tuning of white light characteristics is possible. In addition, laser diode-based white light generation is more favorable compared to LED-based due to higher efficiency and potential cost advantage .
In conclusion, we have demonstrated the growth of InGaN/GaN nanowires directly onto an amorphous quartz substrate using TiN/Ti interlayer and have fabricated LEDs based on the nanowire-on-quartz platform. By utilizing nanowire-based structure, we were able to grow highly crystalline III-nitride material on amorphous quartz. The nanowire-on-quartz LED enables the realization of an LED light source based on the scalable and economical substrate. The fabricated LED emits light at peak wavelength covering yellow-amber-red (peak wavelengths of 590 to 650 nm) with an FWHM of over 120 nm. Capitalizing on the broadly tunable spectral characteristics of the device, we demonstrated a practical generation of a widely tunable white light from 3000 to > 7000 K in a transmission configuration.
AP, JWM, CZ, BJ, TKN, and BSO gratefully acknowledge the financial support from King Abdulaziz City for Science and Technology (KACST), Grant No. KACST TIC R2-FP- 008. This work is partially supported by baseline funding, BAS/1/1614-01-01 from the King Abdullah University of Science and Technology (KAUST).
AP and TKN conceived the idea and designed the investigations, growth experiment, and fabrication process. AP performed the molecular beam epitaxial growth. AP performed the optical characterization and device fabrication. AP and BJ performed the device characterization and color mixing experiment. CZ and DZ performed high-resolution TEM analysis and elemental mapping. AP, J-WM, TKN, and BSO wrote the manuscript. TKN led the molecular beam epitaxy program. BSO, AYA, and AMA supervised the team. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License(http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
- Bruni FJ (2015) Crystal growth of sapphire for substrates for high-brightness, light emitting diodes. Cryst Res Technol 50(1):133–142.View ArticleGoogle Scholar
- Nabulsi F (2015) Implications for LEDs of the shift to large-diameter sapphire wafers. http://www.semiconductor-today.com/features/PDF/semiconductor-today-apr-may-2015-Implications-for.pdf. Accessed 10 Dec 2017.
- Asahi H, Iwata K, Tampo H, Kuroiwa R, Hiroki M, Asami K, Nakamura S, Gonda S (1999) Very strong photoluminescence emission from GaN grown on amorphous silica substrate by gas source MBE. J Cryst Growth 201:371–375.View ArticleGoogle Scholar
- Kim JH, Holloway PH (2004) Room-temperature photoluminescence and electroluminescence properties of sputter-grown gallium nitride doped with europium. J Appl Phys 95(9):4787.View ArticleGoogle Scholar
- Bour DP, Nickel NM, Van de Walle CG, Kneissl MS, Krusor BS, Mei P, Johnson NM (2000) Polycrystalline nitride semiconductor light-emitting diodes fabricated on quartz substrates. Appl Phys Lett 76(16):2182.View ArticleGoogle Scholar
- Choi JH, Zoulkarneev A, Kim SI, Baik CW, Yang MH, Park SS, Suh H, Kim UJ, Bin Son H, Lee JS, Kim M, Kim JM, Kim K (2011) Nearly single-crystalline GaN light-emitting diodes on amorphous glass substrates. Nat Photonics 5(12):763–769.View ArticleGoogle Scholar
- Choi JH, Cho EH, Lee YS, Shim MB, Ahn HY, Baik CW, Lee EH, Kim K, Kim TH, Kim S, Cho KS, Yoon J, Kim M, Hwang S (2014) Fully flexible GaN light-emitting diodes through nanovoid-mediated transfer. Adv Opt Mater 2(3):267–274.View ArticleGoogle Scholar
- Shon JW, Ohta J, Ueno K, Kobayashi A, Fujioka H (2014) Fabrication of full-color InGaN-based light-emitting diodes on amorphous substrates by pulsed sputtering. Sci Rep 4:5325.View ArticleGoogle Scholar
- Bertness KA, Roshko A, Mansfield LM, Harvey TE, Sanford NA (2008) Mechanism for spontaneous growth of GaN nanowires with molecular beam epitaxy. J Cryst Growth 310(13):3154–3158.View ArticleGoogle Scholar
- Hersee SD, Rishinaramangalam AK, Fairchild MN, Zhang L, Varangis P (2011) Threading defect elimination in GaN nanowires. J Mater Res 26(17):2293.View ArticleGoogle Scholar
- Guo W, Banerjee A, Bhattacharya P, Ooi BS (2011) InGaN/GaN disk-in-nanowire white light emitting diodes on (001) silicon. Appl Phys Lett 98(19):193102.View ArticleGoogle Scholar
- Lin HW, Lu YJ, Chen HY, Lee HM, Gwo S (2010) InGaN/GaN nanorod array white light-emitting diode. Appl Phys Lett 97(7):073101.View ArticleGoogle Scholar
- Connie AT, Nguyen HPT, Sadaf SM, Shih I, Mi Z (2014) Engineering the color rendering index of phosphor-free InGaN/(Al)GaN nanowire white light emitting diodes grown by molecular beam epitaxy. J Vac Sci Technol B Microelectron Nanometer Struct 32(2):02–113.Google Scholar
- Frost T, Jahangir S, Stark E, Deshpande S, Hazari A, Zhao C, Ooi BS, Bhattacharya P (2014) Monolithic electrically injected nanowire array edge-emitting laser on (001) silicon. Nano Lett 14(8):4535–4541.View ArticleGoogle Scholar
- Jahangir S, Mandl M, Strassburg M, Bhattacharya P (2013) Molecular beam epitaxial growth and optical properties of red-emitting (λ = 650 nm) InGaN/GaN disks-in-nanowires on silicon. Appl Phys Lett 102(2013):2011–2016.Google Scholar
- Jahangir S, Banerjee A, Bhattacharya P (2013) Carrier lifetimes in green emitting InGaN/GaN disks-in-nanowire and characteristics of green light emitting diodes. Phys Status Solidi (C) Curr Top Solid State Phys 10(5):812–815.View ArticleGoogle Scholar
- Guo W, Zhang M, Banerjee A, Bhattacharya P (2010) Catalyst-free InGaN/GaN nanowire light emitting diodes grown on (001) silicon by molecular beam epitaxy. Nano Lett 10(9):3356–3359.View ArticleGoogle Scholar
- Ristić J, Calleja E, Fernández-Garrido S, Cerutti L, Trampert A, Jahn U, Ploog KH (2008) On the mechanisms of spontaneous growth of III-nitride nanocolumns by plasma-assisted molecular beam epitaxy. J Cryst Growth 310(18):4035–4045.View ArticleGoogle Scholar
- Zhao C, Ng TK, Wei N, Prabaswara A, Alias MS, Janjua B, Shen C, Ooi BS (2016) Facile formation of high-quality InGaN/GaN quantum-disks-in-nanowires on bulk-metal substrates for high-power light-emitters. Nano Lett 16(2):1056–1063.View ArticleGoogle Scholar
- Sarwar AG, Carnevale SD, Yang F, Kent TF, Jamison JJ, McComb DW, Myers RC (2015) Semiconductor nanowire light-emitting diodes grown on metal: a direction toward large-scale fabrication of nanowire devices. Small 11(40):5402–5408.View ArticleGoogle Scholar
- Wölz M, Hauswald C, Flissikowski T, Gotschke T, Fernández-Garrido S, Brandt O, Grahn HT, Geelhaar L, Riechert H (2015) Epitaxial growth of GaN nanowires with high structural perfection on a metallic TiN film. Nano Lett 15(6):3743–3747.View ArticleGoogle Scholar
- Park Y, Jahangir S, Park Y, Bhattacharya P, Heo J (2015) InGaN/GaN nanowires grown on SiO_2 and light emitting diodes with low turn on voltages. Opt Express 23(11):650.View ArticleGoogle Scholar
- Kumaresan V, Largeau L, Oehler F, Zhang H, Mauguin O, Glas F, Gogneau N, Tchernycheva M, Harmand JC (2016) Self-induced growth of vertical GaN nanowires on silica. Nanotechnology 27(13):135602.View ArticleGoogle Scholar
- Zhao S, Kibria MG, Wang Q, Nguyen HPT, Mi Z (2013) Growth of large-scale vertically aligned GaN nanowires and their heterostructures with high uniformity on SiO(x) by catalyst-free molecular beam epitaxy. Nanoscale 5(12):5283–7.View ArticleGoogle Scholar
- Wang W, Yang W, Wang H, Li G (2014) Epitaxial growth of GaN films on unconventional oxide substrates. J Mater Chem C 2(44):9342–9358.View ArticleGoogle Scholar
- Carnevale SD, Yang J, Phillips PJ, Mills MJ, Myers RC (2011) Three-dimensional GaN/AlN nanowire heterostructures by separating nucleation and growth processes. Nano Lett 11(2):866–871.View ArticleGoogle Scholar
- Jahangir S, Schimpke T, Strassburg M, Grossklaus KA, Millunchick JM, Bhattacharya P (2014) Red-emitting (lambda = 610 nm) In0.51Ga0.49N/GaN disk-in-nanowire light emitting diodes on silicon. IEEE J Quantum Electron 50(7):530–537.View ArticleGoogle Scholar
- McCafferty E, Wightman JP (1999) An X-ray photoelectron spectroscopy sputter profile study of the native air-formed oxide film on titanium. Appl Surf Sci 143(1-4):92–100.View ArticleGoogle Scholar
- Kiuchi M, Chayahara A (1994) Titanium nitride for transparent conductors. Appl Phys Lett 64(8):1048–1049.View ArticleGoogle Scholar
- Uchida Y, Ito K, Tsukimoto S, Ikemoto Y, Hirata K, Shibata N, Murakami M (2006) Epitaxial growth of GaN layers on metallic TiN buffer layers. J Elec Materi 35(10):1806–1811.View ArticleGoogle Scholar
- Chen NC, Lien WC, Shih CF, Chang PH, Wang TW, Wu MC (2006) Nitride light-emitting diodes grown on Si (111) using a TiN template. Appl Phys Lett 88(19):109–112.Google Scholar
- Tourbot G, Bougerol C, Glas F, Zagonel LF, Mahfoud Z, Meuret S, Gilet P, Kociak M, Gayral B, Daudin B (2012) Growth mechanism and properties of InGaN insertions in GaN nanowires. Nanotechnology 23(13):135703.View ArticleGoogle Scholar
- Besombes L, Kheng K, Marsal L, Mariette H (2001) Acoustic phonon broadening mechanism in single quantum dot emission. Phys Rev B 63(15):155307.View ArticleGoogle Scholar
- Guo W, Zhang M, Bhattacharya P, Heo J (2011) Auger recombination in III-nitride nanowires and its effect on nanowire light-emitting diode characteristics. Nano Lett 11(4):1434–1438.View ArticleGoogle Scholar
- Nawaz M, Ahmad A (2012) A TCAD-based modeling of GaN/InGaN/Si solar cells. Semicond Sci Technol 27(3):035019.View ArticleGoogle Scholar
- Nihey F, Hongo H, Yudasaka M, Iijima S (2002) A top-gate carbon-nanotube field-effect transistor with a titanium-dioxide insulator. Jpn J Appl Phys 41(Part 2, No. 10A):1049–1051.View ArticleGoogle Scholar
- Feezell DF, Speck JS, DenBaars SP, Nakamura S (2013) Semipolar (2021) InGaN/GaN light-emitting diodes for high-efficiency solid-state lighting. J Disp Technol 9(4):190–198.View ArticleGoogle Scholar
- Thapan K, Arendt J, Skene DJ (2001) An action spectrum for melatonin suppression: evidence for a novel non-rod, non-cone photoreceptor system in humans. J Physiol 535(1):261–267.View ArticleGoogle Scholar
- Chang AM, Aeschbach D, Duffy JF, Czeisler CA (2015) Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proc Natl Acad Sci 112(4):1232–1237.View ArticleGoogle Scholar
- Lee C, Shen C, Oubei HM, Cantore M, Janjua B, Ng TK, Farrell RM, El-Desouki MM, Speck JS, Nakamura S, Ooi BS, DenBaars SP (2015) 2 Gbit/s data transmission from an unfiltered laser-based phosphor-converted white lighting communication system. Opt Express 23(23):29779.View ArticleGoogle Scholar
- Narendran N, Gu Y, Freyssinier JP, Yu H, Deng L (2004) Solid-state lighting: failure analysis of white LEDs. J Cryst Growth 268(3-4 SPEC. ISS.):449–456.View ArticleGoogle Scholar
- Wierer JJ, Tsao JY (2015) Advantages of III-nitride laser diodes in solid-state lighting. Phys Status Solidi (A) Appl Mater Sci 212(5):980–985.View ArticleGoogle Scholar