Estimation of the internal electric field inside (11-22) semipolar GaN/Al_(0.5)Ga_(0.5)N nanostructures and the radiative efficiency at low temperature

摘要

We report on time-integrated and resolved photoluminescence data on self-assembled semipolar (11-22) GaN nanostructures embedded in Al_(0.5)Ga_(0.5)N. It is confirmed that the internal electric field is reduced for semipolar (11-22) orientation. It is shown in particular that the value of the electric field is 450-500 kV/cm for this orientation. The photoluminescence decay time of excitons is used as a probe of the reduction of the internal electric field in the case of semipolar GaN nanostructures. The measured decays are not only controlled by radiative lifetimes, which depend on the fields inside GaN nanostructures, but also on the nonradiative escape of carriers through barriers. The correspondent decay time is found equal to 330 ps. By the study of the decay time as a function of the emission energy, we can determine the evolution of the internal quantum efficiency as a function of the nanostructures height (energy) and to have access to the nonradiative lifetime at low temperature.