Investigation of Key Technologies on Sapphire-Free Light Emitting Diodes for High-Power Blue/White Lighting

 

       We have been working in the area of compound semiconductors, III-Nitrides, II-V, II-VI and IV-IV, nano-structures and quantum structure systems, metalorganic chemical vapor deposition (MOCVD) growth, LEDs and some other related issues.  We have made a significant contribution to a few fields whose impacts affect all parts of the semiconductor, such as light-emitting diodes (LEDs), laser-diodes (LDs), energy-saving light sources, high-resolution displays, and high-power wireless transmitters.  The research activities to advance this technology will assuredly benefit the semiconductor industries on a future scope.  Two major (not all) research accomplishments have been achieved, covering the epitaxial growth and characterization of advanced materials, process and device application, and physics/mechanism investigation.

These 2 research accomplishments include:

(i)        A novel near-UV InGaN LED of laterally overgrown InGaN/AlGaN on a GaN/patterned sapphire template has been fabricated using a combination of a patterned sapphire substrate (PSS) and epitaxial lateral overgrowth (ELOG) techniques.  The ELOG-PSS LED exhibited a 30% enhancement in light output power as compared with that of the conventional GaN/sapphire LED sample. An intensive decrease in dislocation density to a level of 105 cm−2 in the active layer was achieved.

(ii)       A novel chip structure for LED structure/mirror/Cu LEDs without an additional chip-dicing process have been proposed and developed by a combination of wafer bonding, substrate-removing, backside photolithography, and electroplating techniques.  This structure due to Cu substrate having a low turn-on voltage and low resistance produces a novel high-power/high-efficiency LED light source and has high potential in future high-power solid-state lighting.

 

 

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