Color-Tunable and Phosphor-Free White-Light Multilayered Light-Emitting Diodes

• Published in: IEEE transactions on electron devices Vol. 60; no. 1; pp. 333 - 338
• Main Authors: Cheung, Y. F., Choi, H. W.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2013; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Chips; Color; Color tuning; Design. Technologies. Operation analysis. Testing; Devices; Electronics; Emittance; Exact sciences and technology; Image color analysis; Indium gallium nitrides; Integrated circuits; Invariants; Light emitting diodes; light-emitting diode (LED); Microelectronic fabrication (materials and surfaces technology); Optical imaging; Optical mixing; Optoelectronic devices; Semiconductor device measurement; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Three dimensional; Wire; Wires; Ternary compound; Performance evaluation; Tunable circuit; Color tuning; White light; Stacking; Luminescent material; light-emitting diode (LED); Micromachine; Gallium nitride; Microelectronic fabrication; III-VI compound; Wire bonding; Optoelectronic device; Indium nitride; Thermal characteristic; Aluminium oxide; Micromachining; Multiple layer; III-V compound; Light emitting diode; Temperature measurement; Interconnection; Integrated circuit; Color temperature
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2012.2228866

A tightly integrated 3-D RGB light-emitting diode (LED) stack is demonstrated. Chips of identical dimensions are stacked on top of each other, with wire bonds embedded within. This is achieved by integrating laser-micromachined channels onto the sapphire face of InGaN LEDs, serving to accommodate wire bonds from the chip beneath. The resultant structure eliminates leakage of monochromatic light from individual chips, producing optimally mixed emission through the top aperture. The device can emit a wide range of colors and is an efficient phosphor-free white-light LED as well. When emitting at correlated color temperatures (CCTs) of 2362 K, 5999 K, and 7332 K, the device generates ~ 20 lm/W, exhibiting performance invariant of CCT. Thermal characteristics of this multilayered device are investigated via infrared thermometry.