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On the Importance of the Polarity for GaN/InGaN Last Quantum Barriers in III-Nitride-Based Light-Emitting Diodes

In this paper, we investigate the electron injection efficiency in terms of different polarities and different polarization charge densities at the GaN/InGaN interface. We find that the growth orientation for the GaN/InGaN-type last quantum barrier is essentially vital, i.e., the GaN/InGaN-type last quantum barrier is not able to effectively reduce the electron leakage and will degrade the light-emitting diode (LED) performance when the GaN/InGaN interface is [000-1] polarized. However, a suppressed electron leakage and enhanced optical power can be obtained for III-nitride LEDs grown along the [0001] orientation when the GaN/InGaN interface possesses polarization-induced negative charges. We conclude that the polarization-induced negative charges at the [0001] oriented GaN/InGaN interface facilitate the surface depletion in the GaN region, i.e., the conduction band of the GaN region is bent in the way of favoring electron depletion and contributes to an enhanced conduction band barrier height for electrons.