InGaN/GaN多量子阱中由于存在极化效应导致能带弯曲, 并由此导致电子和空穴在空间上被分离, 因此严重降低了GaN基LED的发光效率. 针对此问题, 我们设计了一种组分渐变的量子阱结构, 利用组分与能带的关系对量子阱进行能带调控, 使得量子阱中的能带弯曲减弱. 该方法有效增加了LED的光功率和外量子效率. 电致发光谱测试显示, 在注入电流为35 A/cm2时, 具有能带调控量子阱的LED其外量子效率比传统结构的LED提高了10.6%, 发光功率提高了9.8%. 能带模拟显示, 能带调控后的量子阱中能带倾斜现象减弱, 且空穴浓度明显增加, 因此电子空穴波函数在空间中的重叠面积得到有效提高, 最终提高了辐射复合效率.
国家自然基金委自然基金项目(61306008)
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图1
具有能带调控量子阱的GaN/InGaN多量子阱发光二极管结构示意图
图2
(网络版彩图)具有能带调控量子阱的LED与传统结构的LED光电性能比较. (a) 两种LED样品的IV曲线. 插图: 模拟得到的LED IV曲线; (b) 光输出功率和外量子效率与注入电流的关系曲线; (c) EL发光峰的峰值能量随注入电流的变化曲线
图3
(网络版彩图)传统结构的LED (a)和具有能带调控量子阱的LED (b)的PL发光峰的光子能量与反向偏压的关系曲线. 插图为两种结构的LED样品在不同反向偏压下的PL 发光谱
图4
(网络版彩图)传统结构的LED和具有能带调控量子阱的LED的理论模拟结果. (a) 注入电流为35 A/cm2时, 两种LED样品的量子阱能带图. 插图: 局部能带放大图; (b) 传统结构的LED和具有能带调控量子阱的LED量子阱中空穴浓度对比图
图5
(网络版彩图)计算得到的传统结构的LED和具有能带调控量子阱的LED的模拟结果. (a) 传统结构LED最靠近p型层的量子阱中的电子和空穴波函数; (b) 具有能带调控量子阱的LED最靠近p型层的量子阱中的电子和空穴波函数; (c) 在注入电流为35 A/cm2时, 传统结构的量子阱中和能带调控后的量子阱中的辐射复合效率
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