| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 103 === GaN-based light-emitting diodes (LEDs) are typically grown on c-plane sapphire, or even patterned sapphire substrates (PSSs). In the same growth condition, we adopt wet etching to fabricate our PSSs with structure depth about 0.5µm instead of dry etching with depth up to 1.6µm. However, we find that the quantum-confined Stark effect (QCSE) can be reduced by changing the geometry of PSSs. Moreover, we have found a probable key parameter which dominates the QCSE magnitude, so that we can predict a probable range to further minimize the QCSE.
In the device level, we demonstrate that by reducing QCSE, the optical performance of LED devices such as internal quantum efficiency (IQE) and external quantum efficiency (EQE) can be enhanced, but efficiency droop is larger. After our analysis through the differential of EQE, the efficiency droop should be attributed to the consequence of increasing IQE. In the end, in comparison to the LED devices grown on conventional PSSs, our light output power (LOP) and EQE can reach up to 95% of the conventional one. Therefore, the reduction of QCSE is effective to enhance the performance of LEDs, and it’s potential to be an alternative to fabricate LEDs without changing the crystal growth conditions.
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