Abstract
We demonstrate a highly-efficient, large-area (1x1 mm2) GaN slab light-emitting diode using a vertically directional emitter produced from constructive interference. The vertical radiation can be coupled effectively into leaky modes from the beginning and thus a high-extraction efficiency can be expected with reduced material absorption. The far-field measurements show that the desired vertical emission profiles are obtained by varying the thickness of the dielectric layer between the emitter and bottom silver mirror. With the combination of a light extractor of a randomly textured surface, the output power was increased approximately 1.4 fold compared to a non-patterned device at a standard current of 350 mA without electrical degradation.
Highlights
Light-emitting diodes (LEDs) have made rapid inroads into the classical lightning market owing to energy efficiency and reliable lifetime [1,2,3]
We demonstrate a highly-efficient, large-area (1x1 mm2) GaN slab light-emitting diode using a vertically directional emitter produced from constructive interference
The vertical radiation can be coupled effectively into leaky modes from the beginning and a high-extraction efficiency can be expected with reduced material absorption
Summary
Light-emitting diodes (LEDs) have made rapid inroads into the classical lightning market owing to energy efficiency and reliable lifetime [1,2,3]. By introducing a light extractor, such as a photonic crystal pattern on the top surface of the vertical LEDs, the photons can be coupled efficiently into a leaky medium before they are absorbed by the material [15,16,17,18,19,20]. Such a light extractor cannot render all existing guided modes with different wavevectors to satisfy the phase matching conditions for diffraction [8,9,10]. A significant change in the emission profiles was achieved by appropriately positioning a highreflectivity mirror below the active medium, which resulted in a large extraction efficiency without increasing the operating voltage
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