Effects of optical absorption in deep ultraviolet nanowire light-emitting diodes

We report our study on the effect of optical absorption in nanowire ultraviolet light-emitting diodes (LEDs) using three-dimensional finite difference time domain simulation. Utilizing nanowire structures can avoid the emission of guided modes inside LED structure and redirect the trapped light into radiated modes. The optical loss due to material absorption can be decreased by reducing light propagation path inside the LED structure, and consequently enhance the light extraction efficiency (LEE). Nanowire form factors including size, and density play important roles on the LEE of ultraviolet (UV) nanowire LEDs. In this paper, the nanowire spacing and diameter are considered in simulation to reach maximum LEE. Our results show an unprecedentedly high LEE of ∼34% can be achieved for deep UV emission at 240 nm. Moreover, UV nanowire LEDs with random structure can exhibit LEE of ∼19% which is comparable or higher than that of high efficiency UV thin-film LEDs.