Abstract
AbstarctWe report for the first time a NUV light to white light conversion in a N-B co-doped 6H-SiC (fluorescent SiC) layer containing a hybrid structure. The surface of fluorescent SiC sample contains porous structures fabricated by anodic oxidation method. After passivation by 20 nm thick Al2O3, the photoluminescence intensity from the porous layer was significant enhanced by a factor of more than 12. Using a porous layer of moderate thickness (~10 µm), high-quality white light emission was realized by combining the independent emissions of blue-green emission from the porous layer and yellow emission from the bulk fluorescent SiC layer. A high color rendering index of 81.1 has been achieved. Photoluminescence spectra in porous layers fabricated in both commercial n-type and lab grown N-B co-doped 6H-SiC show two emission peaks centered approximately at 460 nm and 530 nm. Such blue-green emission phenomenon can be attributed to neutral oxygen vacancies and interface C-related surface defects generated dring anodic oxidation process. Porous fluorescent SiC can offer a great flexibility in color rendering by changing the thickness of porous layer and bulk fluorescent layer. Such a novel approach opens a new perspective for the development of high performance and rare-earth element free white light emitting materials.
Highlights
White light-emitting materials have been intensively investigated because of their potential in a wide range of applications in illumination and display systems[1,2,3,4,5]
We proposed an innovative method to achieve white light emission by converting near ultraviolet (NUV) light in a hybrid structure composed of N-B co-doped 6H-SiC and porous layer formed on top of it
An anodic etching process was executed to form the porous layers on the SiC substrate as described in our previous publication[26]
Summary
White light-emitting materials have been intensively investigated because of their potential in a wide range of applications in illumination and display systems[1,2,3,4,5]. The RGB-LEDs based white light sources provide possibility to vary the color-rendering index (CRI) and luminous efficacy[5, 6]. Fluorescent 6H-SiC (band gap = 3.0 eV) co-doped with donor and acceptor is a promising candidate as a phosphor material in NUV-LEDs based white light sources without using rare-earth elements[15]. We proposed an innovative method to achieve white light emission by converting NUV light in a hybrid structure composed of N-B co-doped 6H-SiC and porous layer formed on top of it. By combining the blue-green emission from the porous layer and the yellow emission from the fluorescent SiC substrate, the emitting spectrum can cover the whole visible range. We believe our detailed studies could provide understanding the luminescence mechanisms in porous SiC to realize white light emitting with high CRI and high luminescence efficiency
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