Browsing by Subject "Ingan"

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    On the effect of step-doped quantum barriers in InGaN/GaN light emitting diodes
    (IEEE, 2013) Zhang Z.-H.; Tan S.T.; Ju, Z.; Liu W.; Ji Y.; Kyaw, Z.; Dikme, Y.; Sun, X. W.; Demir, Hilmi Volkan
    InGaN/GaN light-emitting diodes (LEDs) make an important class of optoelectronic devices, increasingly used in lighting and displays. Conventional InGaN/GaN LEDs of c-orientation exhibit strong internal polarization fields and suffer from significantly reduced radiative recombination rates. A reduced polarization within the device can improve the optical matrix element, thereby enhancing the optical output power and efficiency. Here, we have demonstrated computationally that the step-doping in the quantum barriers is effective in reducing the polarization-induced fields and lowering the energy barrier for hole transport. Also, we have proven experimentally that such InGaN/GaN LEDs with Si step-doped quantum barriers indeed outperform LEDs with wholly Si-doped barriers and those without doped barriers in terms of output power and external quantum efficiency. The consistency of our numerical simulation and experimental results indicate the effects of Si step-doping in suppressing quantum-confined stark effect and enhancing the hole injection, and is promising in improving the InGaN/GaN LED performance.
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    ItemOpen Access
    Strain analysis of InGaN/GaN multi quantum well LED structures
    (John Wiley and Sons, 2012-06-22) Cetin, S. S.; Ozturk, M. K.; Ozcelik, S.; Özbay, Ekmel
    Five period InGaN/GaN multi quantum well (MQW) light emitting diode (LED) structures were grown by a metalorganic chemical vapor deposition (MOCVD) system on c-plane sapphire. The structural characteristics as a strain-stress analysis of hexagonal epilayers MQWs were determined by using nondestructive high resolution x-ray diffraction (HRXRD) in detail. The strain/stress analysis in AlN, GaN, and InGaN thin films with a variation of the In molar fraction in the InGaN well layers was conducted based on the precise measurement of the lattice parameters. The a- and c-lattice parameters of the structures were calculated from the peak positions obtained by rocking the theta axis at the vicinity of the symmetric and asymmetric plane reflection angles, followed by the in-plane and out-of-plane strains. The biaxial and hydrostatic components of the strain were extracted from the obtained a- and c-direction strains values.