Origin of Operating Voltage Increase in InGaN-based Light-emitting Diodes under High Injection: Phase Space Filling Effect on Forward Voltage Characteristics

As an attempt to further elucidate the operating voltage increase in InGaN-based light-emitting diodes (LEDs), the radiative and nonradiative current components are separately analyzed in combination with the Shockley diode equation. Through the analyses, we have shown that the increase in operating voltage is caused by phase space filling effect in high injection. We have also shown that the classical Shockley diode equation is insufficient to comprehensively explain the I-V curve of the LED devices since the transport and recombination characteristics of respective current components are basically different. Hence, we have proposed a modified Shockley equation suitable for modern LED devices. Our analysis gives a new insight on the cause of the wall-plug-efficiency drop influenced by such factors as the efficiency droop and the high operating voltage in InGaN LEDs.