Efficiency droop in InSb/AlInSb quantum-well light-emitting diodes Appl. Phys. Lett. 102, 011127 (2013); 10.1063/1.4773182Reduction in efficiency droop, forward voltage, ideality factor, and wavelength shift in polarization-matched GaInN/GaInN multi-quantum-well light-emitting diodes Blue multi-quantum-well light-emitting diodes ͑LEDs͒ with GaInN quantum wells and polarization-matched AlGaInN barriers are grown by metal-organic chemical vapor deposition. The use of quaternary alloys enables an independent control over interface polarization charges and bandgap and has been suggested as a method to reduce electron leakage from the active region, a carrier loss mechanism that can reduce efficiency at high injection currents-an effect known as the efficiency droop. The GaInN / AlGaInN LEDs show reduced forward voltage, reduced efficiency droop, and improved light-output power at large currents compared to conventional GaInN / GaN LEDs.

We report on a significant decrease in the diode-ideality factor of GaInN/GaN multiple quantum well light-emitting diodes (LEDs), from 5.5 to 2.4, as Si-doping is applied to an increasing number of quantum barriers (QBs). The minimum ideality factor of 2.4 is obtained when all QBs are doped. It is shown that polarization-induced triangular band profiles of the undoped QBs are the major cause of the high ideality factors in GaInN/GaN LEDs. Numerical simulations show excellent agreement with the measured ideality factor value and its dependence on QB doping.

Blue light-emitting diodes ͑LEDs͒ with polarization-matched GaInN/GaInN multi-quantum-well ͑MQW͒ active regions are grown by metal-organic vapor-phase epitaxy. The GaInN/GaInN MQW structure reduces the magnitude of polarization sheet charges at heterointerfaces in the active region. The GaInN/GaInN MQW LEDs are shown to have enhanced light-output power, reduced efficiency droop, a lower forward voltage, a smaller diode ideality factor, and decreased wavelength shift, compared with conventional GaInN/GaN MQW LEDs.

Recently, photoluminescence studies using resonant optical excitation in GaInN layers have been used to investigate the physical origin of efficiency droop in GaInN/GaN light-emitting diodes. In these studies, it has been assumed that in the case of resonant excitation, where electron-hole pairs are generated in the GaInN layers only, carrier transport effects play no role. We report that in contrast to this assumption, carrier escape from quantum wells does take place and shows strong dependence upon the duration of excitation and bias conditions. We also discuss the time scales required to reach steady-state conditions under pulsed optical excitation.

III-V nitrides form the backbone of light-emitting diode (LED) technology. However, the relevance of the very strong polarization fields in III-V nitride LEDs remains unclear. Here, we demonstrate the tuning of polarization fields by mechanical force. For compressive strain in a GaInN LED epitaxial layer, we find: (i) redistribution of intensity within the electroluminescence spectrum; (ii) a decrease in the peak efficiency at low current densities; and (iii) an increase in light-output power at high current densities. These findings show the relevance of transport effects in the efficiency droop. V

Optical emission resulting from 405 nm selective photoexcitation of carriers in the GaInN/GaN quantum well ͑QW͒ active region of a light-emitting diode reveals two recombination channels. The first recombination channel is the recombination of photoexcited carriers in the GaInN QWs. The second recombination channel is formed by carriers that leak out of the GaInN QW active region, self-bias the device in forward direction, induce a forward current, and subsequently recombine in the GaInN active region in a spatially distributed manner. The results indicate dynamic carrier transport involving active, confinement, and contact regions of the device.

GaInN/GaN light-emitting triodes having two anodes for promoting the injection of holes into the active region were fabricated and characterized. It was found that the anode-to-anode bias modulates not only the hole-injection efficiency but also the effective light-emitting area and hence the current density through the active region. As the anode-to-anode bias increases, the efficiency at the same current density increases, whereas the efficiency droop decreases substantially, indicating that the limited hole-injection efficiency is one of the dominant mechanisms responsible for the efficiency droop in GaN-based light-emitting diodes.