The Experts below are selected from a list of 120 Experts worldwide ranked by ideXlab platform

Seongju Park - One of the best experts on this subject based on the ideXlab platform.

  • effect of Injection Current Density on electroluminescence in silicon quantum dot light emitting diodes
    Applied Physics Letters, 2009
    Co-Authors: Baek Hyun Kim, R F Davis, Changhee Cho, Seongju Park
    Abstract:

    We report the effect of Injection Current Density on the electroluminescence (EL) from silicon quantum dot (QD) light-emitting diodes. The EL spectra as a function of Injection Current Density were blueshifted and broad. These results are attributed to both the increase in the contribution of small Si QDs in the silicon nitride film due to the increase in the Injection Current Density and the recombination of electron-hole pairs between excited states in the Si QDs due to band bending under high bias.

  • effect of electron blocking layer on efficiency droop in ingan gan multiple quantum well light emitting diodes
    Applied Physics Letters, 2009
    Co-Authors: Sangheon Han, Dongyul Lee, Sangjun Lee, Chuyoung Cho, Minki Kwon, Samdong Lee, Do Young Noh, Dongjoon Kim, Yong Chun Kim, Seongju Park
    Abstract:

    The effect of an electron blocking layer (EBL) on the efficiency droop in InGaN/GaN multiple quantum well light-emitting diodes (LEDs) is investigated. At low Current Density, the LEDs with a p-AlGaN EBL show a higher external quantum efficiency (EQE) than LEDs without an EBL. However, the EQE of LEDs without an EBL is higher than LEDs with an EBL as Injection Current Density is increased. The improved EQE of LEDs without an EBL at high Current Density is attributed to the increased hole Injection efficiency.

Shooujinn Chang - One of the best experts on this subject based on the ideXlab platform.

  • gan based multiquantum well light emitting diodes with tunnel junction cascaded active regions
    IEEE Electron Device Letters, 2015
    Co-Authors: Shooujinn Chang, Chunta Yu
    Abstract:

    We report the fabrication of GaN-based multiquantum well light-emitting diode (LED) with tunnel-junction (TJ)-cascaded active region. It was found from X-ray diffraction spectra that crystal quality of the TJ LED was almost identical to that of the conventional LED. Compared with the conventional LED, it was found that we could achieve 35% higher output power from the TJ LED due to the repeated use of electrons and holes for photon generation. It was also found that the external quantum efficiency drooped by 26.3% and 18.7% for the TJ LED and the conventional LED, respectively, as we increased the Injection Current Density to 80 A/cm $^{\mathrm {\mathbf {2}}}$ . Furthermore, it was found that forward voltages measured with an Injection Current Density of 20 A/cm $^{\mathrm {\mathbf {2}}}$ were 8.94 V for the TJ LED. The large forward voltage observed from the TJ LED should be attributed to the large TJ resistance.

  • gan based multiquantum well light emitting diodes with tunnel junction cascaded active regions
    IEEE Electron Device Letters, 2015
    Co-Authors: Shooujinn Chang, Weiheng Lin
    Abstract:

    We report the fabrication of GaN-based multiquantum well light-emitting diode (LED) with tunnel-junction (TJ)-cascaded active region. It was found from X-ray diffraction spectra that crystal quality of the TJ LED was almost identical to that of the conventional LED. Compared with the conventional LED, it was found that we could achieve 35% higher output power from the TJ LED due to the repeated use of electrons and holes for photon generation. It was also found that the external quantum efficiency drooped by 26.3% and 18.7% for the TJ LED and the conventional LED, respectively, as we increased the Injection Current Density to 80 A/cm $^{\mathrm {\mathbf {2}}}$ . Furthermore, it was found that forward voltages measured with an Injection Current Density of 20 A/cm $^{\mathrm {\mathbf {2}}}$ were 8.94 V for the TJ LED. The large forward voltage observed from the TJ LED should be attributed to the large TJ resistance.

Chunta Yu - One of the best experts on this subject based on the ideXlab platform.

  • gan based multiquantum well light emitting diodes with tunnel junction cascaded active regions
    IEEE Electron Device Letters, 2015
    Co-Authors: Shooujinn Chang, Chunta Yu
    Abstract:

    We report the fabrication of GaN-based multiquantum well light-emitting diode (LED) with tunnel-junction (TJ)-cascaded active region. It was found from X-ray diffraction spectra that crystal quality of the TJ LED was almost identical to that of the conventional LED. Compared with the conventional LED, it was found that we could achieve 35% higher output power from the TJ LED due to the repeated use of electrons and holes for photon generation. It was also found that the external quantum efficiency drooped by 26.3% and 18.7% for the TJ LED and the conventional LED, respectively, as we increased the Injection Current Density to 80 A/cm $^{\mathrm {\mathbf {2}}}$ . Furthermore, it was found that forward voltages measured with an Injection Current Density of 20 A/cm $^{\mathrm {\mathbf {2}}}$ were 8.94 V for the TJ LED. The large forward voltage observed from the TJ LED should be attributed to the large TJ resistance.

Weiheng Lin - One of the best experts on this subject based on the ideXlab platform.

  • gan based multiquantum well light emitting diodes with tunnel junction cascaded active regions
    IEEE Electron Device Letters, 2015
    Co-Authors: Shooujinn Chang, Weiheng Lin
    Abstract:

    We report the fabrication of GaN-based multiquantum well light-emitting diode (LED) with tunnel-junction (TJ)-cascaded active region. It was found from X-ray diffraction spectra that crystal quality of the TJ LED was almost identical to that of the conventional LED. Compared with the conventional LED, it was found that we could achieve 35% higher output power from the TJ LED due to the repeated use of electrons and holes for photon generation. It was also found that the external quantum efficiency drooped by 26.3% and 18.7% for the TJ LED and the conventional LED, respectively, as we increased the Injection Current Density to 80 A/cm $^{\mathrm {\mathbf {2}}}$ . Furthermore, it was found that forward voltages measured with an Injection Current Density of 20 A/cm $^{\mathrm {\mathbf {2}}}$ were 8.94 V for the TJ LED. The large forward voltage observed from the TJ LED should be attributed to the large TJ resistance.

Nelson Tansu - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of Internal Quantum Efficiency and Current Injection Efficiency in III-Nitride Light-Emitting Diodes
    Journal of Display Technology, 2013
    Co-Authors: Hongping Zhao, Guangyu Liu, Jing Zhang, Ronald A. Arif, Nelson Tansu
    Abstract:

    Current Injection efficiency and internal quantum efficiency (IQE) in InGaN quantum well (QW) based light emitting diodes (LEDs) are investigated. The analysis is based on Current continuity relation for drift and diffusion carrier transport across the QW-barrier systems. A self-consistent 6-band k ·p method is used to calculate the band structure for InGaN QW structure. Carrier-photon rate equations are utilized to describe radiative and non-radiative recombination in the QW and the barrier regions, carrier transport and capture time, and thermionic emission leading to carrier leakage out of the QW. Our model indicates that the IQE in the conventional 24-Å In0.28Ga0.72 N -GaN QW structure reaches its peak at low Injection Current Density and reduces gradually with further increase in Current due to the large thermionic carrier leakage. The efficiency droop phenomenon at high Current Density in III-nitride LEDs is thus consistent with the high-driving-Current induced quenching in Current Injection efficiency predicted by our model. The effects of the monomolecular recombination coefficient, Auger recombination coefficient and GaN hole mobility on the Current Injection efficiency and IQE are studied. Structures combining InGaN QW with thin larger energy bandgap barriers such as AlxGa1-xN, lattice-matched AlxIn1-xN, and lattice-matched AlxInyGa1-x-y N have been analyzed to improve Current Injection efficiency and thus minimize droop at high Current Injection in III-nitride LEDs. Effect of the thickness of the larger energy bandgap barriers (AlGaN, AlInN and AlInGaN) on Injection efficiency and IQE are investigated. The use of thin AlGaN barriers shows slight reduction of quenching of the Injection efficiency as the Current Density increases. The use of thin lattice-matched AlInN or AlInGaN barriers shows significant suppression of efficiency-droop in nitride LEDs.

  • Current Injection efficiency induced efficiency-droop in InGaN quantum well light-emitting diodes
    Solid-State Electronics, 2010
    Co-Authors: Hongping Zhao, Guangyu Liu, Ronald A. Arif, Nelson Tansu
    Abstract:

    Abstract Current Injection efficiency and its impact on efficiency-droop in InGaN single quantum well (QW) based light-emitting diodes (LEDs) are investigated. The analysis is based on Current continuity relation for drift and diffusion carrier transport across the QW-barrier system. A self-consistent 6-band k  ·  p method is used to calculate the band structure for InGaN QW. The analysis indicates that the internal quantum efficiency in the conventional 24-A In 0.28 Ga 0.72 N–GaN QW structure reaches its peak at low Injection Current Density and reduces gradually with further increase in Current due to the large carrier thermionic emission. Structures combining 24-A In 0.28 Ga 0.72 N QW with 15-A Al 0.1 Ga 0.9 N barriers show slight reduction in quenching of the Injection efficiency as Current Density increases. The use of 15-A Al 0.83 In 0.17 N barriers shows significant reduction in efficiency-droop (10% reduction of the internal quantum efficiency at Current Density of 620 A/cm 2 ). Thus, InGaN QWs employing thin layers of larger bandgap AlInN barriers suppress the efficiency-droop phenomenon significantly.