We have studied the design, epitaxy, and performance characteristics of deep ultraviolet (UV) AlGaN light emitting diodes (LEDs). By combining the tunnel junction and polarization-engineered AlGaN electron blocking layer, a maximum external quantum efficiency and wall-plug efficiency of 0.35% and 0.21%, respectively, were measured for devices operating at ∼245 nm, which are over one order of magnitude higher than previously reported tunnel junction devices at this wavelength. Severe efficiency droop, however, was measured at very low current densities (∼0.25 A/cm²), which, together with the transverse magnetic (TM) polarized emission, is identified to be the primary limiting factors for the device performance. Detailed electrical and optical analysis further shows that the observed efficiency droop is largely due to an electrical effect instead of an optical phenomenon. Our studies suggest that AlGaN deep UV LEDs with efficiency comparable to InGaN blue-emitting quantum wells can be potentially achieved if issues related to electron overflow and TM polarized emission are effectively addressed.

中文翻译：

---

AlGaN深紫外发光二极管的电子溢出

我们研究了深紫外 (UV) AlGaN 发光二极管 (LED) 的设计、外延和性能特性。通过结合隧道结和极化设计的 AlGaN 电子阻挡层，对于在 ~245 nm 下工作的器件测量到的最大外部量子效率和壁塞效率分别为 0.35% 和 0.21%，这超过一个数量级在该波长下高于先前报道的隧道结器件。然而，在非常低的电流密度 (~0.25 A/cm ²)，它与横向磁 (TM) 极化发射一起被认为是器件性能的主要限制因素。详细的电学和光学分析进一步表明，观察到的效率下降主要是由于电效应而不是光学现象。我们的研究表明，如果与电子溢出和 TM 极化发射相关的问题得到有效解决，则有可能实现效率与 InGaN 蓝光发射量子阱相当的 AlGaN 深紫外 LED。