The authors report on the achievement of full-color nanowire light-emitting diodes (LEDs), with the incorporation of InGaN/AlGaN nanowire heterostructures grown directly on the Si (111) substrates by molecular beam epitaxy. Multiple color emission across nearly the entire visible wavelength range can be realized by varying the In composition in the InGaN quantum dot active region. Moreover, multiple AlGaN shell layers are spontaneously formed during the growth of InGaN/AlGaN quantum dots, leading to the drastically reduced nonradiative surface recombination, and enhanced carrier injection efficiency. Such core–shell nanowire structures exhibit significantly increased carrier lifetime and massively enhanced photoluminescence intensity compared to conventional InGaN/GaN nanowire LEDs. A high color rendering index of ∼98 was recorded for white-light emitted from such phosphor-free core–shell nanowire LEDs.
In this paper, we
report our study on high-performance III-nitride
nanowire light-emitting diodes (LEDs) on copper (Cu) substrates via
the substrate-transfer process. Nanowire LED structures were first
grown on silicon-on-insulator (SOI) substrates by molecular beam epitaxy.
Subsequently, the SOI substrate was removed by combining dry- and
wet-etching processes. Compared to conventional nanowire LEDs on Si,
the nanowire LEDs on Cu exhibit several advantages, including more
efficient thermal management and enhanced light-extraction efficiency
(LEE) because of the usage of metal reflectors and highly thermally
conductive metal substrates. The LED on Cu, therefore, has stronger
photoluminescence, electroluminescence intensities, and better current–voltage
characteristics compared to the conventional nanowire LED on Si. Our
simulation results further confirm the improved device performance
of LEDs on Cu, compared to LEDs on Si. The LEE of the nanowire LED
on Cu is nine times higher than that of the LED on Si at the same
nanowire radius of 60 nm and spacing of 130 nm. Moreover, by engineering
the device-active region, we achieved high-brightness phosphor-free
LEDs on Cu with highly stable white-light emission and high color-rendering
index of ∼95, showing their promising applications in general
lighting, flexible displays, and wearable applications.
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