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Enhanced performance of nitride-based ultraviolet vertical-injection light-emitting diodes by non-insulation current blocking layer and textured surface.

Chiang YC, Lin BC, Chen KJ, Lin CC, Lee PT, Kuo HC - Nanoscale Res Lett (2014)

Bottom Line: For the purpose of light extraction and efficiency enhancement, the nitride-based ultraviolet vertical-injection light-emitting diodes (UV-VLEDs) with non-insulation current blocking layer (n-CBL) and optimized textured surface were fabricated.The optical and electrical characteristics were investigated in this n-CBL UV-VLED.Furthermore, the efficiency of optimized structure was improved by 5 ~ 6 times compared to our reference.

View Article: PubMed Central - PubMed

Affiliation: Institute of Lighting and Energy Photonics, National Chiao Tung University, No.301, Gaofa 3rd Rd., Guiren Dist., Tainan City, 71150, Taiwan, yenchih.chiang@gmail.com.

ABSTRACT
For the purpose of light extraction and efficiency enhancement, the nitride-based ultraviolet vertical-injection light-emitting diodes (UV-VLEDs) with non-insulation current blocking layer (n-CBL) and optimized textured surface were fabricated. The optical and electrical characteristics were investigated in this n-CBL UV-VLED. Furthermore, the efficiency of optimized structure was improved by 5 ~ 6 times compared to our reference.

No MeSH data available.


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Light output power corresponds to different roughness Rms conditions.
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Fig5: Light output power corresponds to different roughness Rms conditions.

Mentions: Figure 4 shows the room-temperature electroluminescence (EL) spectra of these UV-VLEDs under a forward injection current of 350 mA. The luminescent properties of the fabricated UV-VLEDs were measured by a calibrated integrating sphere at room temperature. The emission dominant wavelength for these UV-VLEDs was about 366 ~ 371 nm. As shown in Figure 4, UV-VLED-2 displays superior emission intensity. In addition to discuss changes in intensity, we also observed full width at half maximum (FWHM) and wavelength shift problem. The FWHM of spectrum in these samples is as follows: C-VLED (about 14.8 nm), UV-VLED-1 (about 14.4 nm), UV-VLED-2 (about 13.3 nm), and UV-VLED-3 (about 12.5 nm). From the EL results, the dominant mechanisms for the wavelength shifts and spectral width changes can be attributed to two major reasons: (1) The different stresses on the epitaxial structure due to the thinned GaN substrate. This change of stress can relieve some of the quantum-confined Stark effect (QCSE) on the MQW, which can move the EL peak to shorter wavelength and narrower linewidth [33–36]. (2) With better current spreading or reduced current crowding effect, the local heating of the chip can be greatly improved and such a longer wavelength can be observed in the C-LED, which does not have an n-CBL layer [37–39].In Figure 5, the correlation between the surface morphology and output power is presented. A positive correlation could be observed from the plot. The rougher the surface is, the higher the output power of the device becomes, which is a clear indication of better light extraction. Following this result, we pick some marked devices to execute a detailed optical and electrical characteristic comparison.Figure 4


Enhanced performance of nitride-based ultraviolet vertical-injection light-emitting diodes by non-insulation current blocking layer and textured surface.

Chiang YC, Lin BC, Chen KJ, Lin CC, Lee PT, Kuo HC - Nanoscale Res Lett (2014)

Light output power corresponds to different roughness Rms conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493838&req=5

Fig5: Light output power corresponds to different roughness Rms conditions.
Mentions: Figure 4 shows the room-temperature electroluminescence (EL) spectra of these UV-VLEDs under a forward injection current of 350 mA. The luminescent properties of the fabricated UV-VLEDs were measured by a calibrated integrating sphere at room temperature. The emission dominant wavelength for these UV-VLEDs was about 366 ~ 371 nm. As shown in Figure 4, UV-VLED-2 displays superior emission intensity. In addition to discuss changes in intensity, we also observed full width at half maximum (FWHM) and wavelength shift problem. The FWHM of spectrum in these samples is as follows: C-VLED (about 14.8 nm), UV-VLED-1 (about 14.4 nm), UV-VLED-2 (about 13.3 nm), and UV-VLED-3 (about 12.5 nm). From the EL results, the dominant mechanisms for the wavelength shifts and spectral width changes can be attributed to two major reasons: (1) The different stresses on the epitaxial structure due to the thinned GaN substrate. This change of stress can relieve some of the quantum-confined Stark effect (QCSE) on the MQW, which can move the EL peak to shorter wavelength and narrower linewidth [33–36]. (2) With better current spreading or reduced current crowding effect, the local heating of the chip can be greatly improved and such a longer wavelength can be observed in the C-LED, which does not have an n-CBL layer [37–39].In Figure 5, the correlation between the surface morphology and output power is presented. A positive correlation could be observed from the plot. The rougher the surface is, the higher the output power of the device becomes, which is a clear indication of better light extraction. Following this result, we pick some marked devices to execute a detailed optical and electrical characteristic comparison.Figure 4

Bottom Line: For the purpose of light extraction and efficiency enhancement, the nitride-based ultraviolet vertical-injection light-emitting diodes (UV-VLEDs) with non-insulation current blocking layer (n-CBL) and optimized textured surface were fabricated.The optical and electrical characteristics were investigated in this n-CBL UV-VLED.Furthermore, the efficiency of optimized structure was improved by 5 ~ 6 times compared to our reference.

View Article: PubMed Central - PubMed

Affiliation: Institute of Lighting and Energy Photonics, National Chiao Tung University, No.301, Gaofa 3rd Rd., Guiren Dist., Tainan City, 71150, Taiwan, yenchih.chiang@gmail.com.

ABSTRACT
For the purpose of light extraction and efficiency enhancement, the nitride-based ultraviolet vertical-injection light-emitting diodes (UV-VLEDs) with non-insulation current blocking layer (n-CBL) and optimized textured surface were fabricated. The optical and electrical characteristics were investigated in this n-CBL UV-VLED. Furthermore, the efficiency of optimized structure was improved by 5 ~ 6 times compared to our reference.

No MeSH data available.


Related in: MedlinePlus