在本論文中，我們成功展示出在520nm波段，利用串接的方式來改善大型化後發光二極體的輸出功率以及外部量子效率。我們將串聯的數目從一顆提升到四顆，在相同操作電流下，輸出功率和單顆發光二極體比較確實可以達到四倍的改善。之後，我們進行串接式發光二極體在調變速度上的表現，在相同操作電流下，四顆和單顆有相似的3-dB頻寬約90MHz。 從以上量測結果，我們推論串接的方式確實可以擁有增強外部量子效率的優點，降低發光二極體大型化後面臨到電流壅塞的問題和3-dB頻寬的衰減，雖然串接式發光二極體驅動電壓相對線性地增加，但我們可以將元件運用在特殊操作電壓的系統上，像是車用電力系統方面等。 We demonstrate a linear cascade GaN based Light Emitting Diode (LED) arrays at a wavelength around ~520nm for improving the output power and differential efficiency of a single LED. Arrays with up to four LEDs connected in series, we can achieve four times improvement of output power under the same bias current (differential quantum efficiency) compared with the control, which is a single LED. We have also measured their modulation-speed performance and both devices show similar 3-dB bandwidth (90MHz) under the same bias currents. The measurement results indicate that the cascade connection has the advantages of greatly enhanced external differential efficiency and the ability to be driven by the constant-voltage power supply directly. The current crowding problem and degradation of RC-limited bandwidth in large active area LED can also be minimized through the use of such connection.
