Radiative and nonradiative recombination processes in ultraviolet light-emitting diode composed of an In0.02Ga0.98N active layer

Radiative and nonradiative recombination processes have been studied in ultraviolet In0.02Ga0.98N light-emitting diodes (LEDs), by employing photoinduced voltage, electroreflectance, and time-resolved photoluminescence spectroscopy. It was found that excitons in the In0.02Ga0.98N active layer are weakly localized at low temperature, and delocalized above about 70 K, showing a three-dimensional feature in the temperature dependence of the radiative lifetime. The external quantum efficiency (ηext) of this LED is about ten times higher than the LED whose active layer is composed of GaN. Improvement of the ηext value by the addition of a small amount of In to the active layer is attributed to the suppression of the density of the nonradiative recombination center (NRC), as well as possibly to where the origin of the NRC is changed.