摘 要
本研究是針對具電洞注入層(hole injection layer, HIL)之氮化鎵系列(GaN-based)藍光發光二極體(light-emitting diodes, LEDs)的光電特性進行探討。HIL分別以730、750與780 ℃的溫度成長於最後一層位障(last barrier, LB)與電子阻擋層(electron blocking layer, EBL)之間，其厚度為16 nm且為p型氮化鎵(p-GaN)。實驗結果顯示，HIL成長溫度為730、750與780 ℃之LED，在120 mA下的光輸出功率分別為114.6、112.5與110.5 mW，而效率衰減(efficiency droop)幅度則分別為24.6、25.0與23.5%。730 ℃之HIL LED具較佳光輸出功率，這是因為此樣本之HIL具有較多的電洞濃度，且增加電洞的注入效率。也因此此樣品在低溫EL之光強度衰減與Vf變化都較其他兩者小。相對地，780 ℃之HIL LED具較低efficiency droop，這是因為此樣本的電流散佈較佳，且電洞分佈在主動區中較為均勻。也因此此樣品在Vf、hot/cold factor與抗靜電能力皆具有較佳的結果。
關鍵詞：氮化鎵、發光二極體、電洞注入層
Abstract
In this study, the electrical and optical properties of GaN-based blue light-emitting diodes (LEDs) with hole injection layer (HIL) were investigated. A 16-nm-thick p-GaN HIL inserted between last barrier (LB) and electron blocking layer (EBL) was grown at 730, 750, and 780 ℃. The light output powers of LEDs for HIL grown at 730, 750, and 780 ℃ were 114.6, 112.5, and 110.5 mW, respectively. The efficiency droop ratios of LEDs for HIL grown at 730, 750, and 780 ℃ were 24.6, 25.0, and 23.5%, respectively. The LED with HIL grown at 730 ℃ has a better light output power. This is because this sample has more hole concentrations, and the injection efficiency of the hole increases. Therefore, the light intensity decay and Vf variation of this sample for the low-temperature electroluminescence (EL) were smaller than for other samples. In contrast, the LED with HIL grown at 780 ℃ has a lower efficiency droop. This is attributed to the better current spreading and more uniform hole distribution in the active region. Thus, the Vf, hot/cold factors, and Electrostatic Discharge (ESD) ability of this sample show better performance.
Keywords: GaN, LEDs, hole injection layer