Modified Shockley Equation for GaInN-Based Light-Emitting Diodes: Origin of the Power- Efficiency Degradation Under High Current Injection

As an attempt to elucidate the origin of the power-efficiency (PE) degradation at high current injection for GaInN-based light-emitting diodes, the injection current is quantitatively separated to radiative and nonradiative current components as a function of applied voltage. It is found that the conventional Shockley equation for the current-voltage curve of a Si pn diode is not adequate for the LED since the carrier transport and recombination processes are quite different from those of the Si pn diode. Hence, we propose a diode equation for an LED where the radiative and nonradiative currents are separately expressed as a function of applied voltage. By analyzing the proposed diode equation, it is concluded that the PE degradation at high injection currents is due to the increase of the junction voltage and the decrease of the internal quantum efficiency at the same time. The phenomena can be understood by the insufficient recombination rate in the active quantum wells.