Characteristics of GaN‐based light emitting diode grown on circular convex patterned sapphire substrate

Abstract

We report the characteristics of GaN‐based light‐emitting diode (LED) grown on a circular convex patterned sapphire substrate (CCPSS) and conventional LEDs on a non‐patterned sapphire substrate (PSS) by metal‐organic chemical vapor deposition. A near field scanning optical microscope (NSOM) and micro Raman spectroscopy were employed to investigate the crystalline properties. In NSOM image and spectra of LED on CCPSS, an improved crystalline quality with emission fluctuation feature on the trench region was obtained. However, stress relaxation in this trench region was not achieved due to the presence of voids, indicating a stress concentration at the coalescence region. Compared to conventional LED on non‐PSS, increased internal quantum efficiency (IQE) (41.8%) and reduced leakage currents (40 nA at ‐10 V) were observed in the LED fabricated on CCPSS. The light output power of the LED on CCPSS was approximately two times higher than that of a conventional LED. This enhancement of output power is contributed to increase of IQE and the effective suppression of leakage current by reduction of dislocation density, as well as enhanced light scattering via the circular convex facets. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Enhanced Performance of GaN-Based Light-Emitting Diodes by Using Al Mirror and Atomic Layer Deposition-TiO2/Al2O3Distributed Bragg Reflector Backside Reflector with Patterned Sapphire Substrate

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High-Performance GaN-Based Light-Emitting Diodes on Patterned Sapphire Substrate with a Novel Patterned SiO2/Al2O3Passivation Layer

“…However, when the light is directed to fall within c , it can freely escape from the LED to air. Therefore, several recent studies have focused on improving LEE by changing light trajectories in devices, using different approaches, such as the application of distributed Bragg reflector (DBR) backside reflector, [4][5][6][7] integration of two-dimensional photonic crystal structures, [8][9][10] preparation of patterned sapphire substrate (PSS), [11][12][13][14][15][16] and control of surface textures. [17][18][19][20] In recent years, a surface passivation layer has been introduced to improve the optical and electrical performances of the LEDs both theoretically and experimentally.…”