Stacked GaN/AlN last quantum barrier for high-efficiency InGaN-based green light-emitting diodes
Guoyi Tao, Xiaoyu Zhao, Shengjun Zhou
Abstract
Realization of efficient InGaN-based green light-emitting diodes (LEDs) is highly desirable in solid-state lighting industry. Here, we propose a stacked last quantum barrier (SLQB) GaN/AlN layer for green ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mo>∼</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>550</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">n</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> ) LEDs grown on patterned sapphire substrate to improve the device performance. A green LED with a SLQB achieves a light output power (LOP) of 13 mW at 15 mA, which is 35% higher than that of LEDs with a conventional last quantum barrier (CLQB) GaN layer. In addition, the forward voltage of the green LED with the SLQB is reduced by 0.16 V compared with green LEDs with the CLQB. Simulation results demonstrate that the AlN layer in the SLQB increases the effective barrier height for electrons and alleviates the electron leakage effect. It also enables an intraband tunneling process for holes to inject into the active region, promoting the hole injection efficiency. As a result, we successfully obtain InGaN-based green LEDs with remarkably improved carrier injection efficiency by adopting the SLQB structure.