| Summary: | 碩士 === 國立中興大學 === 精密工程研究所 === 93 === For blue LEDs, due to the lack of native substrates, the GaN crystal structures are commonly grown on sapphire substrates. When blue LEDs driven on high current, the huge joule heating could inhibit LED performance because of the poor thermal conductivity of sapphire. In this work, a vertical type structure for GaN/mirror/Si LED is developed by a combination of wafer bonding and laser lift-off (LLO) techniques.
In the electricity characteristic, the I-V curves of the GaN/mirror/Si and original GaN/sapphire LED samples are nearly the same. This suggests that the LLO and Wafer bonding processes do not adversely affect the LED performance. In the optical characteristic, the luminance intensity of GaN/mirror/Si LED (1456 mcd at 350 mA) is 2.6 times than that of original planar GaN/Sapphire LED (570 mcd at 350 mA). In the heat sink characteristic, as the forward current increase from 20 to 350mA, the junction temperature of Si substrates increases from 23 to 151 C. This junction temperature is lower than sapphire substrate (37C to 246 C at 350mA). Therefore, the heat can be valid transfer from LED junction to heat sink across the Si substrate. It is evident that the device performance of the GaN/mirror/Si LED is better than that of the conventional GaN/sapphire LED. These results indicate that the GaN/mirror/Si LED presents the better performance due to the Si heat sink.
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