Abstract
GaN-based light emitting diodes (LEDs) fabricated on sapphire substrates were successfully transferred onto silicon substrates using a double-transfer technique. Compared with the conventional LEDs on sapphire, the transferred LEDs showed a significant improvement in the light extraction and thermal dissipation, which should be mainly attributed to the removal of sapphire and the good thermal conductivity of silicon substrate. Benefited from the optimized wafer bonding process, the transfer processes had a negligible influence on electrical characteristics of the transferred LEDs. Thus, the transferred LEDs showed a similar current–voltage characteristic with the conventional LEDs, which is of crucial importance for practical applications. It is believed that the double-transfer technique offers an alternative way to fabricate high performance GaN-based thin-film LEDs.
Highlights
As one of the most important light source in nextgeneration solid-state lighting, GaN-based light emitting diodes (LEDs) have been extensively developed in past few years
A comparison shows that the transferred LEDs have a higher concentrated brightness with no spreading of light, indicating an efficient enhancement of the light extraction efficiency
In summary, GaN-based LEDs fabricated on sapphire substrates were transferred onto silicon substrates using a double-transfer technique
Summary
As one of the most important light source in nextgeneration solid-state lighting, GaN-based light emitting diodes (LEDs) have been extensively developed in past few years. GaN-based LEDs have already been used extensively in traffic signals, full-color displays, and backlight units for liquid crystal displays. To further extend the application arm of GaN-based LEDs to general lighting, further improvement on heat dissipation and light extraction efficiency are eagerly required. The poor thermal conductivity of sapphire prevents efficient dissipation of heat generated from the active area during operation, inducing seriously junction heating and the subsequent reduction of internal quantum efficiency. High light extraction, and superior thermal dissipation were demonstrated in the fabricated devices
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