This chapter systematically examines AlN-based devices, focusing on UV-LEDs and power electronics. Despite significant advancements in disinfection, curing, and phototherapy, among others, critical challenges such as low EQE, high driving voltages, and thermal management issues persist due to material defects and inefficient carrier injection. Notably, progress has been achieved through the development of UV-transparent single crystal AlN substrates with nano-photonic light extraction structures and Mg-doping strategies aimed at enhancing p-type conductivity. In power electronics, AlN’s superior properties are demonstrated via lateral and vertical Schottky diodes exhibiting ultra-low leakage currents and high on/off ratios. While early-stage implementations show promise, substrate quality limitations, doping challenges, and scalability issues remain. Commercialization will ultimately depend on holistic optimization of material defects, device architecture, and thermal management to enable reliable operation across applications.