A scattered volume emitter micropixel architecture for ultraefficient light extraction from DUV LEDs

Abstract

Deep ultraviolet light-emitting diodes (DUV LEDs) typically suffer from strong parasitic absorption in the p-epitaxial layer and rear metal contact/mirror. This problem is exacerbated by a significant portion of the multiquantum well (MQW) emissions having a strong out-of-plane dipole component, contributing to emission in widely oblique directions outside the exit cone of the emitting surface. Here, an architecture that exploits heavy oblique emission is proposed by using scattered volume emitter micropixels that are spaced apart and embedded in a low-index dielectric buffer film with a patterned top surface. This approach significantly increases the surface-to-volume ratio of the semiconductor and does not require a high-index (e.g., sapphire) substrate or a lens to achieve high extraction efficiency. Depending on the assumed epilayer absorption, the hybrid wave and ray optical simulations demonstrated a 3- to 6-fold increase in light extraction efficiency compared to that of a conventional planar design with a sapphire substrate reference. An extraction efficiency three times greater than that of a recent nanotextured DUV LED design was also demonstrated. This architecture paves the way for DUV LEDs to have a plug efficiency comparable to that of mercury lamps while still being significantly smaller.