Enhanced injection efficiency and light output in bottom tunnel-junction light-emitting diodes
Enhanced injection efficiency and light output in bottom tunnel-junction light-emitting diodes
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DOI：
10.1364/oe.384021
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发表时间：
2020-02-17
期刊：
影响因子：
3.8
通讯作者：
Turski, Henryk
中科院分区：
文献类型：
--
作者：
Bharadwaj, Shyam;Miller, Jeffrey;Turski, Henryk
最近，在LED中使用底部TJ几何结构，其实现了在常规金属极性取向中的偏振场的N极性样对准，由于改进的注入效率，使得能够增强LED性能。在这里，我们阐明背后的根本原因，通过采用成熟的激光二极管结构与优化的异质结GaN/In0.17Ga0.83N/GaN的TJ和UID GaN间隔物分离的光模式从重掺杂的吸收p-包覆区增强注入效率。在这样的激光器结构中，在电子阻挡层、间隔物和量子势垒界面处的偏振偏移在载流子输运中起着可辨别的作用。通过将顶部TJ结构与底部TJ结构进行比较，并将电致发光、电容-电压和电流-电压特性中的特征与能带图模拟中的N-和Ga-极性极化异质界面的独特特征相关联，我们确定了在低电流下改善的空穴注入和在高电流下改善的电子阻挡，在5个数量级的电流密度（0.015-1000 A/cm（2））下，导致底部TJ器件的更高的注入效率和更高的输出功率。此外，即使添加UID GaN间隔物，差分电阻也是最先进的，低于7 × 10（-4）Ω cm（2）。这些结果突出了底部TJ几何结构用于高效率激光二极管的优点。(C)2020年美国光学学会根据OSA开放获取出版协议的条款
Recently, the use of bottom-TJ geometry in LEDs, which achieves N-polar-like alignment of polarization fields in conventional metal-polar orientations, has enabled enhancements in LED performance due to improved injection efficiency. Here, we elucidate the root causes behind the enhanced injection efficiency by employing mature laser diode structures with optimized heterojunction GaN/In0.17Ga0.83N/GaN TJs and UID GaN spacers to separate the optical mode from the heavily doped absorbing p-cladding regions. In such laser structures, polarization offsets at the electron blocking layer, spacer, and quantum barrier interfaces play discernable roles in carrier transport. By comparing a top-TJ structure to a bottom-TJ structure, and correlating features in the electroluminescence, capacitance-voltage, and current-voltage characteristics to unique signatures of the N- and Ga-polar polarization heterointerfaces in energy band diagram simulations, we identify that improved hole injection at low currents, and improved electron blocking at high currents, leads to higher injection efficiency and higher output power for the bottom-TJ device throughout 5 orders of current density (0.015-1000 A/cm(2)). Moreover, even with the addition of a UID GaN spacer, differential resistances are state-of-the-art, below 7 x 10(-4) Omega cm(2). These results highlight the virtues of the bottom-TJ geometry for use in high-efficiency laser diodes. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement