Browsing by Subject "Current-spreading Layer"

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    InGaN/GaN light-emitting diode with a polarization tunnel junction
    (American Institute of Physics, 2013) Zhang Z.-H.; Tan S.T.; Kyaw, Z.; Ji Y.; Liu W.; Ju, Z.; Hasanov N.; Sun, X. W.; Demir, Hilmi Volkan
    We report InGaN/GaN light-emitting diodes (LED) comprising in situ integrated p(+)-GaN/InGaN/n(+)-GaN polarization tunnel junctions. Improved current spreading and carrier tunneling probability were obtained in the proposed device architecture, leading to the enhanced optical output power and external quantum efficiency. Compared to the reference InGaN/GaN LEDs using the conventional p(+)/n(+) tunnel junction, these devices having the polarization tunnel junction show a reduced forward bias, which is attributed to the polarization induced electric fields resulting from the in-plane biaxial compressive strain in the thin InGaN layer sandwiched between the p(+)-GaN and n(+)-GaN layers. (C) 2013 AIP Publishing LLC.
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    On the effect of N-GaN/P-GaN/N-GaN/P-GaN/N-GaN built-in junctions in the n-GaN layer for InGaN/GaN light-emitting diodes
    (Optical Society of America, 2014-01-07) Kyaw, Z.; Zhang, Z. H.; Liu, W.; Tan, S. T.; Ju, Z. G.; Zhang, X. L.; Ji, Y.; Hasanov, N.; Zhu, B.; Lu, S.; Zhang, Y.; Sun, X. W.; Demir, Hilmi Volkan
    N-GaN/P-GaN/N-GaN/P-GaN/N-GaN (NPNPN-GaN) junctions embedded between the n-GaN region and multiple quantum wells (MQWs) are systematically studied both experimentally and theoretically to increase the performance of InGaN/GaN light emitting diodes (LEDs) in this work. In the proposed architecture, each thin P-GaN layer sandwiched in the NPNPN-GaN structure is completely depleted due to the built-in electric field in the NPNPN-GaN junctions, and the ionized acceptors in these P-GaN layers serve as the energy barriers for electrons from the n-GaN region, resulting in a reduced electron over flow and enhanced the current spreading horizontally in the n-GaN region. These lead to increased optical output power and external quantum efficiency (EQE) from the proposed device. (C) 2014 Optical Society of America
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    ItemOpen Access
    On the mechanisms of InGaN electron cooler in InGaN/GaN light-emitting diodes
    (Optical Society of America, 2014) Zhang, Z. H.; W. L.; Tan, S. T.; Ju, Z.; Ji, Y.; Kyaw, Z.; Zhang, X.; Hasanov, N.; Zhu, B.; Lu, S.; Zhang, Y.; Sun, X. W.; Demir, Hilmi Volkan
    Electron overflow limits the quantum efficiency of InGaN/GaN light-emitting diodes. InGaN electron cooler (EC) can be inserted before growing InGaN/GaN multiple quantum wells (MQWs) to reduce electron overflow. However, detailed mechanisms of how the InGaN EC contributes to the efficiency improvement have remained unclear so far. In this work, we theoretically propose and experimentally demonstrate an electron mean-free-path model, which reveals the InGaN EC reduces the electron mean free path in MQWs, increases the electron capture rate and also reduces the valence band barrier heights of the MQWs, in turn promoting the hole transport into MQWs. (C) 2014 Optical Society of America