The School of Electrical Engineering, Korea University , Seoul 136-701, Korea.
ACS Appl Mater Interfaces. 2016 Mar 2;8(8):5453-7. doi: 10.1021/acsami.5b12127. Epub 2016 Feb 17.
We report performance improvements in near-ultraviolet (NUV) light-emitting diodes (LEDs) using various metal-doped indium tin oxide (ITO/metals). Metals with an orbital energy gap greater than that of an In atom (e.g., Ti, Ga, Ge, and Al) are deposited on ITO, and subsequent annealing is performed to improve optical transmittance of ITO due to effective bandgap increase via the linear combination of atomic orbitals, as well as electrical conductivity; thus, current spreading via metal-doping effect at the surface of ITO. As a result, the ITO/metals (annealed at 550 °C, 1 min) exhibit 90.5-94.7% transmittance at 385 nm and a specific contact resistance of 2.1-3.0 × 10(-3) Ω cm(2), whereas the reference ITOs exhibit 76.5-89.5% and 3.2-4.5 × 10(-3) Ω cm(2), respectively. Compared to NUV LEDs using conventional ITO (60 nm), the InGaN/AlGaInN NUV LED using ITO (110 nm)/metal (3 nm) on average exhibits a 70% increase in light output power at 100 mA and a 2% decrease in forward voltage at 20 mA, with more uniform and brighter emission images. We also identified the origin for the improvement by analyzing the surface of ITO/metals using X-ray photoelectron spectroscopy and Auger electron spectroscopy. This approach could offer a simple, effective way to enhance the overall efficiency of conventional NUV LEDs using ITO.
我们报告了使用各种金属掺杂氧化铟锡（ITO/金属）的近紫外（NUV）发光二极管（LED）的性能改进。将轨道能隙大于铟原子的金属（例如 Ti、Ga、Ge 和 Al）沉积在 ITO 上，然后进行退火，由于原子轨道的线性组合导致有效能带隙增加，以及导电性提高，从而提高 ITO 的光透过率；因此，通过 ITO 表面的金属掺杂效应实现电流扩展。结果，ITO/金属（在 550°C 下退火 1 分钟）在 385nm 处表现出 90.5-94.7%的透过率和 2.1-3.0×10(-3) Ω cm(2)的特定接触电阻，而参考 ITO 则分别表现出 76.5-89.5%和 3.2-4.5×10(-3) Ω cm(2)的透过率和特定接触电阻。与使用传统 ITO（60nm）的 NUV LED 相比，使用 ITO（110nm）/金属（3nm）的 InGaN/AlGaInN NUV LED 在 100mA 时的光输出功率平均增加了 70%，在 20mA 时的正向电压降低了 2%，同时具有更均匀和更亮的发射图像。我们还通过分析 X 射线光电子能谱和俄歇电子能谱来确定 ITO/金属表面的改善原因。这种方法可以为使用 ITO 的传统 NUV LED 提供一种简单有效的提高整体效率的方法。
