Quenching of the Efficiency Droop in Cubic Phase InGaAlN Light-Emitting Diodes

We show that the coexistence of strong internal polarization and large carrier (i.e., electron and hole) effective mass accounts for ~51% of the efficiency droop under high current densities in traditional (hexagonal-phase) indium-gallium-aluminum-nitride (InGaAlN) light-emitting diodes (h-LEDs) compared to cubic-phase InGaAlN LEDs (c-LEDs). Our analysis based on variational technique on c-LEDs predicts an enhancement of the current density at the onset of the droop, inherently present in green c-LEDs. These effects are a consequence of the polarization-free nature and small carrier effective mass of c-LEDs. Our analysis indicates that, by overlooking the electron-hole wave function overlap, the well-known ABC model is suspected to overestimate the Auger coefficient, leading to questionable conclusions on the efficiency droop. In turn, it shows that the c-LED efficiency droop is much immune to the Auger electron-hole asymmetry, the increase in the Auger coefficient, and, thus, efficiency degradation mechanisms.