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Growth and characterization of InGaN-based light-emitting diodes on patterned sapphire substrates

Growth and characterization of InGaN-based light-emitting diodes on patterned sapphire substrates. 陳詠升. W.K. Wang, D.S. Wuu, S.H. Lin, S.Y. Huang, K.S. Wen, R.H. Horng. Journal of Physics and Chemistry of Solids 69 (2008) 714–718. Outline. Introduction Experimental details

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Growth and characterization of InGaN-based light-emitting diodes on patterned sapphire substrates

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  1. Growth and characterization of InGaN-based light-emitting diodes on patterned sapphire substrates 陳詠升 W.K. Wang, D.S. Wuu, S.H. Lin, S.Y. Huang, K.S. Wen, R.H. Horng Journal of Physics and Chemistry of Solids 69 (2008) 714–718

  2. Outline • Introduction • Experimental details • Results and discussion • Conclusions • References

  3. Introduction • Highdislocation density will influence the device characteristics,such as device lifetime, electronmobility, and the quantumefficiency of radiative recombination. • In this work, we propose a new approach for growing a high-quality GaN film using the patterned sapphire substrates(PSSs) with different depth of grooves (Dg). This technique eliminates the dislocations and increases the emitted light extraction efficiency.

  4. Experimental details 1.0μm 0.5 μm 0 μm Schematic diagram of the LED structure grown on grooved sapphire substrate. The atomic-force-microscopy micrograph shows thepatternedsubstrate after dry etching.

  5. Results and discussion Cross-section TEM image of GaN epilayer grown on (a)conventional sapphire substrate and (b) patterned sapphire substrate(Dg =1.0 mm).

  6. X-ray rocking curves of (0 0 0 2) reflections for GaN grownon PSSwith different etching depths (Dg =0, 0.5, 1.0 μm).

  7. Output power as a function of injection current for PSS InGaNLEDs with different etching depths (Dg =0, 0.5, 1.0 μm).

  8. Trace-Pro simulated ray extraction ratio of PSS LEDs withvarious Dg values.

  9. Reliability test of relative luminous intensity of PSS InGaN LEDswith different etching depths (Dg = 0, 0.5, 1.0 μm).

  10. PSS LED (Dg =1.0 μ m) (22%) conventional LED (28%) Light output patterns of the PSS LEDs with various groovedepths. The forward current was driven at 20 mA.

  11. Conclusions • As much as 33% increased light emission intensity of the PSS LED was obtained at a forward current of 20 mA. • The output power and external quantum efficiency of the PSS LED at 20mA were measured to be 7.1mW and 10.1% • From the TEM study, the use of PSS was confirmed to be an efficient way to reduce the TDs in the GaN microstructure.

  12. References • Y.D. Wang, K.Y. Zang, S.J. Chua, S. Tripathy, H.L. Zhou, C.G.Fonstad, Improvement of microstructuraland optical properties ofGaN layer on sapphire bynanoscale lateral epitaxial overgrowth,Appl. Phys.Lett. 88 (2006) 211908. • W.K. Wang, D.S. Wuu, S.H. Lin, P. Han, R.H. Horng, T.C. Hsu,D.T.C. Huo, M.J. Jou, Y.H. Yu, A. Lin, Efficiencyimprovement ofnear-ultraviolet InGaN LEDs using patterned sapphiresubstrates,IEEE J. Quantum Electron. 41 (2005) 1403–1408.

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