Cubic GaN and InGaN/GaN quantum wells
Cubic GaN and InGaN/GaN quantum wells
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DOI：
10.1063/5.0097558
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发表时间：
2022-12
影响因子：
15
通讯作者：
D. Binks;P. Dawson;R. Oliver;D. Wallis
中科院分区：
文献类型：
--
作者：
D. Binks;P. Dawson;R. Oliver;D. Wallis
基于六边形InGaN/GaN量子威尔斯阱的LED是用于许多照明应用的主导技术。然而，它们对于绿色和琥珀色发射以及在高驱动电流下的发光效率仍然有限。相反，在立方相中生长量子威尔斯是一种有前途的替代方案，因为与六方GaN相比，它受益于减小的带隙，并且没有可能降低辐射复合率的强极化场。在20世纪90年代，生长立方GaN的最初尝试采用分子束外延，但现在，也可以使用金属有机化学气相沉积。尽管如此，高相纯度需要仔细注意生长条件和任何不需要的六方相的定量。与六方GaN相比，其中穿透位错是关键，在其目前的成熟状态下，立方GaN中最重要的扩展结构缺陷是堆垛层错。这些改变立方GaN膜的光学性质并传播到有源层中。在量子威尔斯和电子阻挡层中，观察到合金元素在层错处的偏析，导致量子线和极化发射的形成。这一观察形成了对立方InGaN量子威尔斯阱的光学性质的不断发展的理解的一部分，立方InGaN量子阱也提供了比其极性六方对应物更短的复合寿命。在p型掺杂方面也有越来越多的专业知识，包括通过退火激活掺杂剂。总体而言，立方GaN已经从学术好奇心迅速转变为器件应用的真实的前景，与极性六方材料相比，具有提供特定性能优势的潜力。
LEDs based on hexagonal InGaN/GaN quantum wells are dominant technology for many lighting applications. However, their luminous efficacy for green and amber emission and at high drive currents remains limited. Growing quantum wells instead in the cubic phase is a promising alternative because, compared to hexagonal GaN, it benefits from a reduced bandgap and is free of the strong polarization fields that can reduce the radiative recombination rate. Initial attempts to grow cubic GaN in the 1990s employed molecular beam epitaxy, but now, metal-organic chemical vapor deposition can also be used. Nonetheless, high phase purity requires careful attention to growth conditions and the quantification of any unwanted hexagonal phase. In contrast to hexagonal GaN, in which threading dislocations are key, at its current state of maturity, the most important extended structural defects in cubic GaN are stacking faults. These modify the optical properties of cubic GaN films and propagate into active layers. In quantum wells and electron blocking layers, segregation of alloying elements at stacking faults has been observed, leading to the formation of quantum wires and polarized emission. This observation forms part of a developing understanding of the optical properties of cubic InGaN quantum wells, which also offer shorter recombination lifetimes than their polar hexagonal counterparts. There is also growing expertise in p-doping, including dopant activation by annealing. Overall, cubic GaN has rapidly transitioned from an academic curiosity to a real prospect for application in devices, with the potential to offer specific performance advantages compared to polar hexagonal material.