High Power Vertical-structure GaN-based LEDs with Improved Current Spreading and Blocking Designs

Conference Paper · July 2007with5 Reads
DOI: 10.1109/DRC.2007.4373661 · Source: IEEE Xplore
Conference: Device Research Conference, 2007 65th Annual
Based on experimental results which reveal that the contact of indium-zinc-oxide (IZO) and IZO/Ti to n-GaN layer is Schottky and ohmic, respectively, localized Ti deposition associated with a transparent IZO layer is proposed to serve as both current blocking and current spreading layer. In addition, an anisotropic mesa etching on the surface layer (n-GaN) of regular vertical-conducting metal-substrate GaN-based light-emitting diodes (VM-LEDs) is also proposed to further decrease the resistance difference between the outside path and the inner one. The effectiveness of the proposed schemes were verified by a two-dimensional device simulator (ISE-TCAD), which indicates that significant immune of current crowding under cathode contact pad would be possible once an optimal combination of the n-GaN layer etching depth and width, IZO thickness, and Schottky blocking width has been achieved. In experiments, 40-mil LEDs with an anisotropic mesa etching of 400 mum in width and 2 mum in depth, 200 mum in Schottky blocking width, and a 300-nm-thick IZO layer have been successfully fabricated. Typical improvement in light output power by about 25% at an injection current of 350 mA as compared to the regular VM-LEDs has been obtained.
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April 2007 · IEEE Photonics Technology Letters · Impact Factor: 2.11
    Through the use of selective nickel (Ni) electroplating, patterned laser liftoff technique, and surface roughing of the top n-GaN epilayer, a novel process for the fabrication of vertical-structured metal-substrate GaN-based light-emitting diodes (VM-LEDs) to avoid difficulties in Ni substrate dicing and improve device yield was proposed and demonstrated. In conjunction with a sidewall... [Show full abstract]
    June 2006 · IEEE Photonics Technology Letters · Impact Factor: 2.11
      In this study, the performance of vertical-structured high-power GaN-based light-emitting diodes (VM-LEDs) with a transparent and low-resistant indium-zinc oxide (IZO) film as a current spreading layer (CSL) was investigated. Nickel electroplating and patterned laser liftoff techniques were employed for the transfer of sapphire substrate to nickel substrate. The novel IZO CSL atop n-side-up... [Show full abstract]
      October 2009 · Japanese Journal of Applied Physics · Impact Factor: 1.13
        The performance of vertical-structure metallic-substrate GaN-based light-emitting diodes (VM-LEDs) with a patterned SiO2 film as the current-blocking layer (CBL) was investigated. From theoretical calculations of current and light distributions and experimental results on current-voltage (I-V) and light output power-current (L-I) characteristics, we found that SiO2 CBL inserted under the n-pad... [Show full abstract]
        June 2006
          An anisotropic laser etching to the surface layer (n-GaN) of vertical-structured GaN-based light-emitting diodes (LEDs) associated with a transparent conducting layer (TCL) to release current crowding effect (CCE) for better light emission uniformity and higher optical efficiency is proposed and demonstrated. The theory behind the proposed scheme was verified by a two-dimensional device... [Show full abstract]
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