Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, CO, United States of America.
Nanotechnology. 2019 Jun 7;30(23):234001. doi: 10.1088/1361-6528/ab07ed. Epub 2019 Feb 18.
Ultraviolet light-emitting diodes fabricated from N-polar AlGaN/GaN core-shell nanowires (NWs) with p-i-n structure produced electroluminescence at 365 nm with ∼5× higher intensities than similar GaN homojunction LEDs. The improved characteristics were attributed to localization of spontaneous recombination to the NW core, reduction of carrier overflow losses through the NW shell, and elimination of current shunting. Poisson-drift-diffusion modeling indicated that a shell Al mole fraction of x = 0.1 in Al Ga N effectively confines electrons and injected holes to the GaN core region. AlGaN overcoat layers targeting this approximate Al mole fraction were found to possess a low-Al-content tip and high-Al-content shell, as determined by scanning transmission electron microscopy. Photoluminescence spectroscopy further revealed the actual Al mole fraction to be NW diameter-dependent, where the tip and shell compositions converged towards the nominal flux ratio for large diameter NWs.
采用 N 极性 AlGaN/GaN 核壳纳米线 (NWs) 制成的紫外发光二极管具有 p-i-n 结构，在 365nm 处产生电致发光，其强度比类似的 GaN 同质结 LED 高出约 5 倍。改进的特性归因于自发复合局域到 NW 核，通过 NW 壳减少载流子溢出损耗，以及消除电流分流。泊松-漂移-扩散建模表明，AlGaN 壳中 Al 摩尔分数 x = 0.1 的 Al 有效地将电子和注入的空穴限制在 GaN 核区。通过扫描透射电子显微镜发现，针对这个近似 Al 摩尔分数的 AlGaN 覆盖层具有低 Al 含量的尖端和高 Al 含量的壳。光致发光光谱进一步表明，实际的 Al 摩尔分数与 NW 直径有关，在大直径 NWs 中，尖端和壳的组成趋于名义通量比。
