Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

Alnoor, Hatim; Pozina, Galia; Khranovskyy, Volodymyr; Liu, Xianjie; Iandolo, Donata; Willander, Magnus; Nur, Omer

doi:10.1063/1.4947593

Cited by 35 publications

(33 citation statements)

References 33 publications

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“…Below are a description and discussion of these results that were published in the six appended papers. [34,52,[56][57][58][59] …”

Section: Resultsmentioning

confidence: 99%

“…[56][57][58] Moreover, high crystal quality well-oriented Co-doped ZnO NRs were also synthesized by manipulating the way of mixing the synthesizer solution. [34,52,59] All these parameters were precisely selected considering that the final properties of the ZnO NRs are susceptible to the synthesis conditions.…”

Section: Hydrothermal Synthesis Methodsmentioning

confidence: 99%

“…[35,53] In this thesis, two types of seed layers were prepared, and their effect on the performance of the synthesized ZnO-based heterojunction LEDs was systematically studied. [57,58] [58] For the synthesis of the pure and Co-doped ZnO NRs, the prepared seed layer solutions were then spun coated 3-4 times on the substrates with a spin speed of 3000 round per minute (rpm) for 3 minutes. This step was then followed by annealing in a normal laboratory oven for 10 minutes at 120 ºC and subsequently submerged in the ZnO synthesis solution.…”

Section: Zno Seed Layer Preparationmentioning

confidence: 99%

“…The synthesis solutions used were 0.05 M concentration for the zinc nitrate and 0.075 M concentration for the HMTA with a molar ratio of 1:2. [56][57][58] Then we investigated the effect of stirring durations of the synthesis solutions on the optical properties of the ZnO NRs. [56] Four synthesis precursor's (solution) consisting of zinc nitrate and HMTA were dissolved separately in 100 ml DI-water each and were then carefully mixed and stirred at room-temperature for 1, 3, 5 and 15 h, respectively, with a stirring speed of 600 rpm.…”

Section: Synthesis Of Zno Nrsmentioning

confidence: 99%

“…[57,58] The p-type and n-type contacts were evaporated in a circular area of diameter ~ 2 mm. The fabrication process is illustrated in Figure 3.4.…”

Section: N-zno Nrs/p-gan-based Heterojunction Ledsmentioning

confidence: 99%

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Toward the Optimization of Low-temperature Solution-based Synthesis of ZnO Nanostructures for Device Applications

Alnoor¹

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One-dimensional (1D) nanostructures (NSs) of Zinc Oxide (ZnO) such as nanorods (NRs) have recently attracted considerable research attention due to their potential for the development of optoelectronic devices such as ultraviolet (UV) photodetectors and light-emitting diodes (LEDs). The potential of ZnO NRs in all these applications, however, would require synthesis of high crystal quality ZnO NRs with precise control over the optical and electronic properties. It is known that the optical and electronic properties of ZnO NRs are mostly influenced by the presence of native (intrinsic) and impurities (extrinsic) defects. Therefore, understanding the nature of these intrinsic and extrinsic defects and their spatial distribution is critical for optimizing the optical and electronic properties of ZnO NRs. However, identifying the origin of such defects is a complicated matter, especially for NSs, where the information on anisotropy is usually lost due to the lack of coherent orientation. Thus, the aim of this thesis is towards the optimization of the lowtemperature solution-based synthesis of ZnO NRs for device applications. In this connection, we first started with investigating the effect of the precursor solution stirring durations on the deep level defects concentration and their spatial distribution along the ZnO NRs. Then, by choosing the optimal stirring time, we studied the influence of ZnO seeding layer precursor’s types, and its molar ratios on the density of interface defects. The findings of these investigations were used to demonstrate ZnO NRs-based heterojunction LEDs. The ability to tune the point defects along the NRs enabled us further to incorporate cobalt (Co) ions into the ZnO NRs crystal lattice, where these ions could occupy the vacancies or interstitial defects through substitutional or interstitial doping. Following this, high crystal quality vertically welloriented ZnO NRs have been demonstrated by incorporating a small amount of Co into the ZnO crystal lattice. Finally, the influence of Co ions incorporation on the reduction of core-defects (CDs) in ZnO NRs was systematically examined using electron paramagnetic resonance (EPR)

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“…Below are a description and discussion of these results that were published in the six appended papers. [34,52,[56][57][58][59] …”

Section: Resultsmentioning

confidence: 99%

Section: Hydrothermal Synthesis Methodsmentioning

confidence: 99%

Section: Zno Seed Layer Preparationmentioning

confidence: 99%

Section: Synthesis Of Zno Nrsmentioning

confidence: 99%

“…[57,58] The p-type and n-type contacts were evaporated in a circular area of diameter ~ 2 mm. The fabrication process is illustrated in Figure 3.4.…”

Section: N-zno Nrs/p-gan-based Heterojunction Ledsmentioning

confidence: 99%

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Toward the Optimization of Low-temperature Solution-based Synthesis of ZnO Nanostructures for Device Applications

Alnoor¹

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Fe‐Doped p‐ZnO Nanostructures/n‐GaN Heterojunction for “Blue‐Free” Orange Light‐Emitting Diodes

Zhao

Xiong

Han

et al. 2017

Advanced Optical Materials

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In order to obtain the necessary band gap for light‐emitting diodes (LEDs) with zero emission at blue wavelengths (“blue‐free”), quasi‐3D nanostructures of p‐type Fe‐doped zinc oxide (ZnO:Fe) are fabricated on an n‐type GaN substrate. The ZnO:Fe nanostructure comprises an array of vertical nanowires attached at the nodes of a 2D network. Elemental analysis and field‐effect‐transistor (FET) and current–voltage (I–V) measurements indicate the successful iron‐doping of ZnO. After doping, the ZnO exhibits p‐type conductivity, a local‐charge‐reservoir layer, and an abundance of Fe‐related deep levels. The cathodoluminescence (CL), photoluminescence (PL) at various temperatures (down to 4.65 K), and electroluminescence (EL) confirm the creation of Fe‐related donor and acceptor levels. New donor levels may be attributed to the substitution of Fe for some Zn sites (“FeZn”), while new acceptor levels may be due to the bind of FeZn with Zn vacancies, (producing FeZn–VZn pairs). These doping‐induced energy levels are helpful in restricting the intrinsic ZnO UV and blue emission, and a stable blue‐free orange LED device is achieved. It has chromaticity coordinates of ∼(0.483, 0.447) and a color temperature of ∼2574 K under bias voltages of 6–16 V, making it potentially applicable to electronic display systems.

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Seed layer synthesis effect on the concentration of interface defects and emission spectra of ZnO nanorods/p‐GaN light‐emitting diode

Alnoor

Pozina

Willander

et al. 2016

Physica Status Solidi (a)

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As the low‐temperature aqueous chemical synthesis (LT‐ACS), holds great promises for the synthesis of one‐dimensional (1D) ZnO nanostructure‐based light‐emitting diodes (LEDs) and hence require parameter tuning for optimal performance. N‐ZnO nanorods (NRs)/p‐GaN heterojunction LEDs have been synthesized by the LT‐ACS using ZnO nanoparticle (NPs) seed layers prepared with different precursor solutions. The effect of these seed layers on the interface defect properties and emission intensity of the as‐synthesized n‐Zn/p‐GaN heterojunction LEDs has been demonstrated by spatially resolved cathodoluminescence (CL) and electroluminescence (EL) measurements, respectively. A significant reduction of the interface defects in the n‐ZnO NRs/p‐GaN heterostructure synthesized from a seed layer prepared from zinc acetate (ZnAc) with a mixture of potassium hydroxide (KOH) and hexamethylenetetramine (HMTA) (donated as ZKH seed) compared with those prepared from ZnAc and KOH (donated as ZK seed) is observed as revealed by spatially resolved CL. Consequently, the LEDs based on n‐ZnO NRs/p‐GaN prepared from ZKH seed show an improvement in the yellow emission (∼578 nm) compared to that based on the ZK seed as deduced from the electroluminescence measurements. The improvement in the yellow EL emission on the ZKH LED probably attributed to the low presence of the non‐radiative defect as deduced by light‐output current (L–I) characteristics analysis.

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Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

Cited by 35 publications

References 33 publications

Toward the Optimization of Low-temperature Solution-based Synthesis of ZnO Nanostructures for Device Applications

Toward the Optimization of Low-temperature Solution-based Synthesis of ZnO Nanostructures for Device Applications

Fe‐Doped p‐ZnO Nanostructures/n‐GaN Heterojunction for “Blue‐Free” Orange Light‐Emitting Diodes

Seed layer synthesis effect on the concentration of interface defects and emission spectra of ZnO nanorods/p‐GaN light‐emitting diode

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