Growth and characterization of InGaNbased light-emitting diodes on patterned
sapphire substrates
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
陳詠升
Outline
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Introduction
Experimental details
Results and discussion
Conclusions
References
Introduction
• High dislocation density will influence the device
characteristics,such as device lifetime, electron mobility,
and the quantum efficiency 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.
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 the patterned substrate after
dry etching.
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).
X-ray rocking curves of (0 0 0 2) reflections for GaN grown on
PSS with different etching depths (Dg =0, 0.5, 1.0 μm).
Output power as a function of injection current for PSS InGaN LEDs with
different etching depths (Dg =0, 0.5, 1.0 μm).
Trace-Pro simulated ray extraction ratio of PSS LEDs with various Dg
values.
Reliability test of relative luminous intensity of PSS InGaN LEDs with
different etching depths (Dg = 0, 0.5, 1.0 μm).
PSS LED (Dg =1.0 μ m) (22%)
conventional LED (28%)
Light output patterns of the PSS LEDs with various groove depths. The
forward current was driven at 20 mA.
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.
References
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Y.D. Wang, K.Y. Zang, S.J. Chua, S. Tripathy, H.L. Zhou, C.G.Fonstad,
Improvement of microstructural and optical properties of GaN layer on
sapphire by nanoscale 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, Efficiency improvement of near-ultraviolet InGaN
LEDs using patterned sapphire substrates,IEEE J. Quantum Electron. 41 (2005)
1403–1408.