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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.


Related in: MedlinePlus

Schematic diagram of UV-VLEDs. Schematic diagram of (a) C-VLED, (b) UV-VLED with n-CBL and larger pyramid textured surface (UV-VLED-1), (c) UV-VLED with n-CBL and smaller pyramid textured surface (UV-VLED-2), and (d) UV-VLED only with n-CBL (UV-VLED-3).
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Fig1: Schematic diagram of UV-VLEDs. Schematic diagram of (a) C-VLED, (b) UV-VLED with n-CBL and larger pyramid textured surface (UV-VLED-1), (c) UV-VLED with n-CBL and smaller pyramid textured surface (UV-VLED-2), and (d) UV-VLED only with n-CBL (UV-VLED-3).

Mentions: Regular semiconductor processes are used to fabricate the devices. The multilayer metal systems Ni(5 Å)/Ag(1,000 Å)/Ti(300 Å)/Pt(500 Å)/Ti(300 Å)/Pt(500 Å) and Cr(300 Å)/Pt(500 Å)/Au(12,000 Å) were deposited by electron beam evaporation at a pressure of 1 × 10-6 Torr to serve as the p-contact and bonding metal. After the metal deposition, the specimen was bonded to the Si substrate with Cr(300 Å)/Pt(500 Å)/Au(12,000 Å) at 220°C for 30 min. Through a wafer bonding technique, the substrate is transferred into a highly thermal conductive silicon substrate to provide great thermal dissipation, and this new substrate can potentially provide a platform for light-emitting devices to achieve high brightness operation. Then, the sapphire substrate was removed by an LLO process. A KrF excimer laser at a wavelength of 248 nm with a pulse width of 25 ns was used for the LLO process. The laser with a beam size of 0.3 mm × 0.3 mm was incident from the backside of the substrate onto the sapphire/n-GaN interface to decompose GaN into Ga and N. After the sapphire substrate removal, the specimen was dipped into a HCl solution to get rid of the residual Ga on the n-GaN. The details of the LLO process are described in [16]. To eliminate the possible UV absorption caused by laser damage in the n-GaN target layer, this layer was removed by inductively coupled plasma (ICP) dry etching. Additionally, in order to enhance light extraction, a 40% KOH solution at 90°C was used to create the surface roughness of the n-GaN epilayer under different time durations: (a) 1 min and (b) 2 min. As shown in Figure 1b,c, a multiple-layer structure of Ti(300 Å)/Al(1,500 Å)/Ni(1,000 Å)/Au(1.2 μm) was deposited on the surface of the n-GaN epilayer to serve as the n-contact. Finally, the UV-VLED chip was cut into square pieces with a dimension of 1.15 mm × 1.15 mm. In addition, a similar UV-VLED structure without the n-CBL and textured surface was also fabricated for comparison, denoted as conventional vertical LEDs (C-VLED). Note that the depth of the etched n-GaN of C-VLED is 2.2 μm. Figure 1 shows the schematic diagram of these UV-VLEDs.Figure 1


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)

Schematic diagram of UV-VLEDs. Schematic diagram of (a) C-VLED, (b) UV-VLED with n-CBL and larger pyramid textured surface (UV-VLED-1), (c) UV-VLED with n-CBL and smaller pyramid textured surface (UV-VLED-2), and (d) UV-VLED only with n-CBL (UV-VLED-3).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Fig1: Schematic diagram of UV-VLEDs. Schematic diagram of (a) C-VLED, (b) UV-VLED with n-CBL and larger pyramid textured surface (UV-VLED-1), (c) UV-VLED with n-CBL and smaller pyramid textured surface (UV-VLED-2), and (d) UV-VLED only with n-CBL (UV-VLED-3).
Mentions: Regular semiconductor processes are used to fabricate the devices. The multilayer metal systems Ni(5 Å)/Ag(1,000 Å)/Ti(300 Å)/Pt(500 Å)/Ti(300 Å)/Pt(500 Å) and Cr(300 Å)/Pt(500 Å)/Au(12,000 Å) were deposited by electron beam evaporation at a pressure of 1 × 10-6 Torr to serve as the p-contact and bonding metal. After the metal deposition, the specimen was bonded to the Si substrate with Cr(300 Å)/Pt(500 Å)/Au(12,000 Å) at 220°C for 30 min. Through a wafer bonding technique, the substrate is transferred into a highly thermal conductive silicon substrate to provide great thermal dissipation, and this new substrate can potentially provide a platform for light-emitting devices to achieve high brightness operation. Then, the sapphire substrate was removed by an LLO process. A KrF excimer laser at a wavelength of 248 nm with a pulse width of 25 ns was used for the LLO process. The laser with a beam size of 0.3 mm × 0.3 mm was incident from the backside of the substrate onto the sapphire/n-GaN interface to decompose GaN into Ga and N. After the sapphire substrate removal, the specimen was dipped into a HCl solution to get rid of the residual Ga on the n-GaN. The details of the LLO process are described in [16]. To eliminate the possible UV absorption caused by laser damage in the n-GaN target layer, this layer was removed by inductively coupled plasma (ICP) dry etching. Additionally, in order to enhance light extraction, a 40% KOH solution at 90°C was used to create the surface roughness of the n-GaN epilayer under different time durations: (a) 1 min and (b) 2 min. As shown in Figure 1b,c, a multiple-layer structure of Ti(300 Å)/Al(1,500 Å)/Ni(1,000 Å)/Au(1.2 μm) was deposited on the surface of the n-GaN epilayer to serve as the n-contact. Finally, the UV-VLED chip was cut into square pieces with a dimension of 1.15 mm × 1.15 mm. In addition, a similar UV-VLED structure without the n-CBL and textured surface was also fabricated for comparison, denoted as conventional vertical LEDs (C-VLED). Note that the depth of the etched n-GaN of C-VLED is 2.2 μm. Figure 1 shows the schematic diagram of these UV-VLEDs.Figure 1

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