Department of Electrical and Computer Engineering, McGill University , 3480 University Street, Montreal, Quebec H3A 0E9, Canada.
Department of Electrical Engineering and Computer Science, Center for Photonics and Multiscale Nanomaterials, University of Michigan , Ann Arbor, Michigan 48109, United States.
Nano Lett. 2017 Feb 8;17(2):1212-1218. doi: 10.1021/acs.nanolett.6b05002. Epub 2017 Jan 18.
To date, semiconductor light emitting diodes (LEDs) operating in the deep ultraviolet (UV) spectral range exhibit very low efficiency due to the presence of large densities of defects and extremely inefficient p-type conduction of conventional AlGaN quantum well heterostructures. We have demonstrated that such critical issues can be potentially addressed by using nearly defect-free AlGaN tunnel junction core-shell nanowire heterostructures. The core-shell nanowire arrays exhibit high photoluminescence efficiency (∼80%) in the UV-C band at room temperature. With the incorporation of an epitaxial Al tunnel junction, the p-(Al)GaN contact-free nanowire deep UV LEDs showed nearly one order of magnitude reduction in the device resistance, compared to the conventional nanowire p-i-n device. The unpackaged Al tunnel junction deep UV LEDs exhibit an output power >8 mW and a peak external quantum efficiency ∼0.4%, which are nearly one to two orders of magnitude higher than previously reported AlGaN nanowire devices. Detailed studies further suggest that the maximum achievable efficiency is limited by electron overflow and poor light extraction efficiency due to the TM polarized emission.
迄今为止，由于存在高密度的缺陷和传统 AlGaN 量子阱异质结构中极低效的 p 型传导，工作在深紫外 (UV) 光谱范围内的半导体发光二极管 (LED) 的效率非常低。我们已经证明，使用几乎无缺陷的 AlGaN 隧道结核壳纳米线异质结构可以潜在地解决这些关键问题。核壳纳米线阵列在室温下的 UV-C 波段表现出高的光致发光效率（约 80%）。通过引入外延 Al 隧道结，与传统的纳米线 p-i-n 器件相比，p-（Al）GaN 无接触纳米线深紫外 LED 的器件电阻降低了近一个数量级。未封装的 Al 隧道结深紫外 LED 表现出>8 mW 的输出功率和>0.4%的峰值外量子效率，比之前报道的 AlGaN 纳米线器件高近一到两个数量级。详细的研究进一步表明，由于 TM 偏振发射，最大可实现的效率受到电子溢出和光提取效率差的限制。
