Unprecedented high-temperature operational stability of interfacial silicide-free ultraviolet-A multiple-quantum- disk AlGaN nanowire-based light-emitting diodes on metal is achieved and investigated. Reasonable variations in device operational parameters across a wide range of temperatures demonstrate the high quality of the layer interfaces and efficient carrier injection. We previously presented ultraviolet-A quantum-confined Al<sub>x</sub>Ga<sub>1-x</sub>N/Al<sub>y</sub>Ga<sub>1-y</sub>N nanowire-based light-emitting diodes and studied their steady-state electro- and photo- luminescent characteristics at room temperature. Herein, we significantly expand the scope of our previous work by investigating the operational stability of the device across a wide range of temperatures (-50-100°C) with conformal parylene-C deposition, forming a nanowire forest as a polymer/nanowire three-dimensional composite material. This work constitutes part of a larger study into the operational stability of ultraviolet light-emitting diode chemical sensors at a wide range of temperatures for operation in harsh environments such as in downhole oil exploration.
AlGaN-based UV-C LEDs (260-300 nm) remain inefficient compared to InGaN visible LEDs due to optically absorptive layers limiting light extraction, optical polarization, and poor material quality. Sapphire, the most popular substrate material, is transparent and inexpensive but has many disadvantages in material quality and device performance. In contrast, SiC has small lattice mismatch with AlN (~1%), similar crystal structure, more chemically stable and contains no oxygen, which degrades the IQE and compensates holes. We report low threading dislocations density (TDD) AlN on SiC (TDD < 7x10<sup>8</sup>cm<sup>-2</sup>) by metalorganic chemical vapor deposition (MOCVD). We demonstrate innovative thin-film flipchip (TFFC) LEDs with 7.8 mW at 95 mA at 278.5 nm grown on AlN/SiC with TDD~1x10<sup>9</sup> cm<sup>-2</sup>. (Respectively, EQE and WPE are 1.8% and 0.6%.) We also demonstrate that KOH roughening does not impact the IV voltage of TFFC LED. KOH roughening enhanced the light extraction efficiency (LEE) by 100% and ~180% for UV LEDs with 10 nm p-GaN and 5 nm p-GaN, respectively.