Non-radiative recombination and efficiency of InGaN quantum well light emitting diodes.

The electroluminescence efficiency of InGaN LEDs is surprisingly high for structures which have high defect concentrations due to growth on mismatched substrates. We have measured the high-injection non-radiative lifetime (tau (nr)) in InGaN LEDs by analysis of the light current characteristics. We find that the values of tau (nr) decrease from 18ns at 200K to 5ns at 400K. This behaviour is thermally activated with an activation energy of 40meV which is compatible with the hypothesis that the temperature dependence is due to thermal delocalisation of carriers from potential minima caused by modest fluctuations in In composition in the quantum well. We determine the internal quantum efficiency to lie between 52% and 65% at room temperature over the current range employed.