Browsing by Author "Bi, W."

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    A charge inverter for III-nitride light-emitting diodes
    (American Institute of Physics Inc., 2016) Zhang Z.-H.; Zhang, Y.; Bi, W.; Geng, C.; Xu S.; Demir, Hilmi Volkan; Sun, X. W.
    In this work, we propose a charge inverter that substantially increases the hole injection efficiency for InGaN/GaN light-emitting diodes (LEDs). The charge inverter consists of a metal/electrode, an insulator, and a semiconductor, making an Electrode-Insulator-Semiconductor (EIS) structure, which is formed by depositing an extremely thin SiO2 insulator layer on the p+-GaN surface of a LED structure before growing the p-electrode. When the LED is forward-biased, a weak inversion layer can be obtained at the interface between the p+-GaN and SiO2 insulator. The weak inversion region can shorten the carrier tunnel distance. Meanwhile, the smaller dielectric constant of the thin SiO2 layer increases the local electric field within the tunnel region, and this is effective in promoting the hole transport from the p-electrode into the p+-GaN layer. Due to the improved hole injection, the external quantum efficiency is increased by 20% at 20 mA for the 350 × 350 μm2 LED chip. Thus, the proposed EIS holds great promise for high efficiency LEDs.
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    ItemOpen Access
    On the hole accelerator for III-nitride light-emitting diodes
    (American Institute of Physics Inc., 2016) Zhang Z.-H.; Zhang, Y.; Bi, W.; Geng, C.; Xu S.; Demir, Hilmi Volkan; Sun, X. W.
    In this work, we systematically conduct parametric studies revealing the sensitivity of the hole injection on the hole accelerator (a hole accelerator is made of the polarization mismatched p-electron blocking layer (EBL)/p-GaN/p-AlxGa1-xN heterojunction) with different designs, including the AlN composition in the p-AlxGa1-xN layer, and the thickness for the p-GaN layer and the p-AlxGa1-xN layer. According to our findings, the energy that the holes obtain does not monotonically increase as the AlN incorporation in the p-AlxGa1-xN layer increases. Meanwhile, with p-GaN layer or p-AlxGa1-xN layer thickening, the energy that the holes gain increases and then reaches a saturation level. Thus, the hole injection efficiency and the device efficiency are very sensitive to the p-EBL/p-GaN/p-AlxGa1-xN design, and the hole accelerator can effectively increase the hole injection if properly designed.