Unusual temperature dependence of electroluminescence intensity in blue InGaN single quantum well diodes

Abstract

Temperature dependence of electroluminescence (EL) spectral intensity of the super-bright blue InGaN single quantum well (SQW) light emitting diodes (LEDs) has been carefully investigated over a wide temperature range (T=15–300 K) and as a function of injection current level (0.1–10 mA) in comparison with high quality GaAs SQW–LEDs. When T is slightly decreased to 180 K, the EL intensity efficiently increases in both cases due to the reduced non-radiative recombination processes. However, further decreasing T below 100 K, striking differences exist in EL intensity as well as injection current dependences between the two types of diodes. That is, the EL efficiency at lower T is found to be quite low for the blue diode in strong contrast to that of red GaAs SQW–LED where significant enhancement of the EL efficiency persists down to 15 K. These results indicate that the carrier capture efficiency of the blue SQW diode is unusually worse at lower T than at T=180–300 K, reflecting the unique radiative recombination processes under the presence of high-density dislocation (1010cm−2).