White Light Emission from Fluorescent SiC with Porous Surface

Lu, Weifang; Ou, Yiyu; Fiordaliso, Elisabetta Maria; Iwasa, Yoshimi; Jokubavičius, Valdas; Syväjärvi, Mikael; Kamiyama, Satoshi; Petersen, Paul Michael; Ou, Haiyan

doi:10.1038/s41598-017-10771-7

Cited by 33 publications

(40 citation statements)

References 38 publications

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“…Fluorescent SiC is a promising phosphor for white LEDs due to its potential in achieving the requirements for low cost, a high color-rendering index, high emission intensity and efficiency, and high durability [ 5 , 10 ]. Despite SiC being an indirect bandgap semiconductor (3.0 eV), nitrogen (N) and boron (B) co-doped 6H–SiC can provide bright yellow–orange (around 578 nm) luminescence from donor–acceptor pair (DAP) emissions [ 5 , 10 , 11 , 12 ]. Moreover, porous structures fabricated in fluorescent SiC can emit simultaneous blue–green light, which is attributed to surface-defects-related emissions [ 12 , 13 , 14 ].…”

Section: Introductionmentioning

confidence: 99%

Voltage-Controlled Anodic Oxidation of Porous Fluorescent SiC for Effective Surface Passivation

Yanai

Yamane

et al. 2020

Nanomaterials

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This study investigated the fabrication of porous fluorescent SiC using a constant voltage-controlled anodic oxidation process. The application of a high, constant voltage resulted in a spatial distinction between the porous structures formed inside the fluorescent SiC substrates, due to the different etching rates at the terrace and the large step bunches. Large, dendritic porous structures were formed as the etching process continued and the porous layer thickened. Under the conditions of low hydrofluoric acid (HF) concentration, the uniformity of the dendritic porous structures through the entire porous layer was considerably improved compared with the conditions of high HF concentration. The resulting large uniform structure offered a sizable surface area, and promoted the penetration of atomic layer-deposited (ALD) Al2O3 films (ALD–Al2O3). The emission intensity in the porous fluorescent SiC was confirmed via photoluminescence (PL) measurements to be significantly improved by a factor of 128 after ALD passivation. With surface passivation, there was a clear blueshift in the emission wavelength, owing to the effective suppression of the non-radiative recombination rate in the porous structures. Furthermore, the spatial uniformity of emitted light was examined via PL mapping using three different excitation lasers, which resulted in the observation of uniform and distinctive emissions in the fluorescent SiC bulk and porous areas.

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Section: Introductionmentioning

confidence: 99%

Voltage-Controlled Anodic Oxidation of Porous Fluorescent SiC for Effective Surface Passivation

Yanai

Yamane

et al. 2020

Nanomaterials

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“…These seem to cause a self‐passivation effect on the SiC:Al crystallites and hinder formation of a native oxide layer. Hydrogen is known to saturate dangling bonds in semiconductors, especially in silicon, but also in SiC and therewith deactivating potential luminescence quenching or charge trapping sites . The presence of a high density of Si–H bonds and absence of a Si‐dangling bond signal (BE < 99 eV) for SiC:Al here, indicates successful deactivation of these defects.…”

Section: Discussionmentioning

confidence: 99%

“…The deactivation of dangling bonds and prevention of insulating oxide layers is vital for efficient charge transfer and transport in this material, for example, in LEDs or catalysis. This sort of surface passivation is usually only achieved by post‐treatment such as alumina or titania deposition on freshly HF‐etched SiC surfaces . In contrast, our synthesis route via sol‐gel precursors and carbothermal reduction allows to obtain SiC growth, doping, and surface passivation as a one‐step process.…”

Section: Discussionmentioning

confidence: 99%

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Characterization of Surface and Structure of In Situ Doped Sol‐Gel‐Derived Silicon Carbide

et al. 2018

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Silicon carbide (SiC), is an artificial semiconductor used for high-power transistors and blue LEDs, for its extraordinary properties. SiC will be attractive for more applications, but large-scale or large-surface area fabrication, with control over defects and surface is challenging. Sol-gel based techniques are an affordable alternative toward such requirements. This report describes two types of microcrystalline SiC derived after carbothermal reduction from sol-gel-based precursors, one with nitrogen added, the other aluminum. Characterization of their bulk, structure, and surface shows that incorporation of dopants affects the formation of polytypes and surface chemistry. Nitrogen leads exclusively to cubic SiC, exhibiting a native oxide surface. Presence of aluminum instead promotes growth of hexagonal polytypes and induces self-passivation of the crystallites' surface during growth. This is established by hydrogenation of silicon bonds and formation of a protecting aluminum carbonate species. XPS provides support for the suggested mechanism. This passivation is achieved in only one step, solely by aluminum in the precursor. Hence, it is shown that growth, doping and passivation of SiC can be performed as "one-pot synthesis". Material without insulating oxide and a limited number of defects is highly valuable for applications involving surface-sensitive charge-transfer reactions, therefore the potential of this method is significant.

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“…Meanwhile, efforts have also been made toward enhancing the light extraction efficiency of f-SiC by using, e.g., antireflective subwavelength conical 6 and wavelength-scale nanodome structures, 7 which have resulted in enhancements of 66.3% and 138%, respectively. Later on, the hybrid f-SiC structure combining as-grown f-SiC with the porous f-SiC surface layer 8 has achieved white light emission with a color rendering index (CRI) as high as 81.1. As the luminescence efficiency is the cornerstone of the lighting source based on f-SiC where the emission quality is quite sensitive to the doping levels of both n-and p-type dopants, a lot of efforts have been made toward optimizing the doping conditions.…”

Section: Introductionmentioning

confidence: 99%

Influence of negative-U centers related carrier dynamics on donor-acceptor-pair emission in fluorescent SiC

Wei

Tarekegne

2018

Journal of Applied Physics

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E 1 /E 2 defects are the typical negative-U centers in n-type 6H silicon carbide (SiC). They are the main contributors to non-radiative recombination, which limits the carrier lifetime. In this study, two fluorescent 6H silicon carbide (f-SiC) samples and one bulk substrate were characterized via time-resolved photoluminescence (TRPL) and static photoluminescence (PL) measurements, where all the samples were nitrogen-boron co-doped 6H n-type. The existence of E 1 /E 2 defects, which caused the diminution of the internal quantum efficiency (IQE) and luminescence intensity of each sample, was confirmed by applying a carrier dynamics model based on negative-U centers. The carrier dynamics simulation reveals that the density of the E 1 /E 2 defects in bulk 6H SiC is two orders of magnitude higher than that of the f-SiC sample, causing much lower PL intensity in the bulk substrate compared to the two f-SiC samples. The IQE of the two f-SiC samples was extracted from the corresponding TRPL results, where the contrast between their IQE was further confirmed by the related PL measurement results. The slight difference in IQE between the two f-SiC samples was attributed to slightly different E 1 /E 2 defect concentrations. On the other hand, by implementing a steady-state donor-acceptor-pair (DAP) recombination calculation, it was found that the f-SiC sample with lower IQE had a higher DAP transition probability due to the higher doping level. This prompted further optimizations in the f-SiC crystal growth conditions in order to decrease the E 1 /E 2 defects while maintaining the correct doping parameters.

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White Light Emission from Fluorescent SiC with Porous Surface

Cited by 33 publications

References 38 publications

Voltage-Controlled Anodic Oxidation of Porous Fluorescent SiC for Effective Surface Passivation

Voltage-Controlled Anodic Oxidation of Porous Fluorescent SiC for Effective Surface Passivation

Characterization of Surface and Structure of In Situ Doped Sol‐Gel‐Derived Silicon Carbide

Influence of negative-U centers related carrier dynamics on donor-acceptor-pair emission in fluorescent SiC

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