U-shape phenomenon in the efficiency-versus-current curves in AlGaN-based deep-ultraviolet light-emitting diodes

The efficiency of an AlGaN deep-ultraviolet light-emitting diode with peak emission wavelength of 285nm is investigated as a function of current over a wide range of temperatures (110K to 300K). We find that the efficiency-versus-current curve exhibits unique and distinct features over the entire temperature range including three points of inflection, a u-shape phenomenon which the efficiency increases again after the minimum, and higher low-temperature efficiency than room-temperature efficiency at high-current density regime.