The efficiency droop in GaInN/GaN multiple-quantum well (MQW) light-emitting diodes (LEDs) is investigated. Measurements show that the efficiency droop, occurring under high injection conditions, is unrelated to junction temperature. Furthermore, the photoluminescence output as a function of excitation power shows no droop, indicating that the droop is not related to MQW efficiency but rather to the recombination of carriers outside the MQW region. Simulations show that polarization fields in the MQW and electron blocking layer (EBL) enable the escape of electrons from the MQW region and thus are the physical origin of the droop. It is shown that through the use of proper quaternary AlGaInN compositions, polarization effects are reduced, thereby minimizing droop and improving efficiency. The GaInN LED structures investigated here are grown on n-type conducting c-plane GaN substrates by metal-organic vapor-phase epitaxy. After the pretreatment of GaN substrates in NH3 and H2 ambient at 1100 °C, a 3-μm-thick n-type GaN layer is deposited, followed by a 5 MQW active region. The MQW consists of 3-nm-thick Ga0.8In0.2N wells and 18-nm-thick GaN:Si barriers. Subsequently, a p-type Al0.13Ga0.87N:Mg electron blocking layer (EBL) is grown, followed by a p-type GaN cladding layer. Vertical LED structures 1×1 mm2 in size are fabricated; the unencapsulated devices emit at λ=450 nm and have an output power of 250 mW at a current of 350 mA (J=35 A/cm2). To establish the possible dependence of efficiency droop on junction temperature, temperature-dependent light-output-power-versus-current measurements are performed. The LED chips—mounted directly on a hot plate—are operated in pulsed current-injection mode to eliminate Joule heating. The relative output power is measured for heat-sink temperatures ranging from 25 to 150 °C using a Si photodetector. The absolute output power of the devices is measured by using an integrating sphere. The simulations reveal that polarization fields in the MQW active region and the EBL enhance the leakage of injected electrons into the p-type GaN cladding layer, and thus cause the efficiency droop. Theoretical considerations show that quaternary AlGaInN quantum barriers and EBL can be polarization matched to the QWs and GaN, respectively, to reduce carrier escape as well as efficiency droop while strongly enhancing the device efficiency at high current levels.The efficiency droop in GaInN/GaN multiple-quantum well (MQW) light-emitting diodes (LEDs) is investigated. Measurements show that the efficiency droop, occurring under high injection conditions, is unrelated to junction temperature. Furthermore, the photoluminescence output as a function of excitation power shows no droop, indicating that the droop is not related to MQW efficiency but rather to the recombination of carriers outside the MQW region. Simulations show that polarization fields in the MQW and electron blocking layer (EBL) enable the escape of electrons from the MQW region and thus are the physical origin of the droop. It is shown that through the use of proper quaternary AlGaInN compositions, polarization effects are reduced, thereby minimizing droop and improving efficiency. The GaInN LED structures investigated here are grown on n-type conducting c-plane GaN substrates by metal-organic vapor-phase epitaxy. After the pretreatment of GaN substrates in NH3 and H2 ambient at 1100 °C, a 3-μm-thick n-type GaN layer is deposited, followed by a 5 MQW active region. The MQW consists of 3-nm-thick Ga0.8In0.2N wells and 18-nm-thick GaN:Si barriers. Subsequently, a p-type Al0.13Ga0.87N:Mg electron blocking layer (EBL) is grown, followed by a p-type GaN cladding layer. Vertical LED structures 1×1 mm2 in size are fabricated; the unencapsulated devices emit at λ=450 nm and have an output power of 250 mW at a current of 350 mA (J=35 A/cm2). To establish the possible dependence of efficiency droop on junction temperature, temperature-dependent light-output-power-versus-current measurements are performed. The LED chips—mounted directly on a hot plate—are operated in pulsed current-injection mode to eliminate Joule heating. The relative output power is measured for heat-sink temperatures ranging from 25 to 150 °C using a Si photodetector. The absolute output power of the devices is measured by using an integrating sphere. The simulations reveal that polarization fields in the MQW active region and the EBL enhance the leakage of injected electrons into the p-type GaN cladding layer, and thus cause the efficiency droop. Theoretical considerations show that quaternary AlGaInN quantum barriers and EBL can be polarization matched to the QWs and GaN, respectively, to reduce carrier escape as well as efficiency droop while strongly enhancing the device efficiency at high current levels.