A large-area (1 x 1 mm) vertical conductive GaN-mirror-Cu light-emitting diode (LED) fabricated, using the laser liftoff and electroplating techniques is demonstrated. Selective p-GaN top area. was first electroplated by the thick copper film, and then an excimer laser was employed to separate the GaN thin film from the sapphire substrate. The luminance, intensity of the vertical conductive p-side-down GaN-mirror-Cu LED presented about 2.7 times in magnitude as compared with that of the original GaN-sapphire LED (at 20 mA). The light output power for the GaN-mirror-Cu LED was about twofold stronger (at 500 mA). A more stable peak wavelength shift under high current injection was also observed

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An n-side-up GaN/mirror(Pd/Au)/Si light-emitting diode (LED) with surface texturing has been fabricated by a combination of wafer-bonding, laser lift-off, and surface texturing techniques. Two concentrations of KOH solution were used to roughen the n-GaN surface. In order to obtain a uniformly roughened surface, the solution was heated instead of being subjected to photoirradiation. The GaN/Pd/Au/Si LEDs with surface texturing exhibited a maximum luminance intensity of 130 mcd (at 20 mA) with a forward voltage of 3.2 V. The luminance intensity is over two times larger than that of the original planar GaN/ sapphire LEDs (at 20 mA). Under high current injection, the surface textured GaN/Pd/Au/Si LEDs also showed a more stable luminance intensity. This feature is attributed to the Si substrate providing a good heat sink and surface roughening enhancing the external quantum efficiency. Furthermore, the n-side-up GaN/mirror(Pd/Au)/Si LEDs with surface texturing have been demonstrated to have high reliability.

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