Degradation behavior of deep ultraviolet LEDs: the role of polarization induced doping in p-AlGaN layer

Abstract Polarization-induced doping in p-aluminum gallium nitride (p-AlGaN) consisting of composition gradient AlGaN has been widely utilized in AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) to enhance hole injection. Yet the presence of polarization doping on the degradation behavior of DUV-LED still remains largely unexplored. In this work, the time-dependent electrical, optical properties and degradation mechanisms of 273 nm AlGaN-based DUV-LEDs with and without polarization doping were comprehensively investigated. Compared to DUV-LED incorporating bulk p-AlGaN, polarization-doped DUV-LED reveals lower leakage current, higher output power and longer lifetime due to its unique compositionally graded structure. The external quantum efficiency versus current density ( J ) curves before and after electrical stress was fitted by the ABC + f(n) model. A four-times enhancement in Auger recombination coefficient was obtained for conventional LEDs after aging, while a 185% increase in non-radiative recombination coefficient was identified in polarization doped DUV-LEDs, suggesting different roles played between bulk and polarization-doped p-AlGaN during the device aging process.