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InGaN/GaN multi-quantum-well blue (461±4 nm) light emitting diodes with higher electroluminescence intensity are obtained by postgrowth thermal annealing at 720 °C in O2-ambient. Based on our first-principle total-energy calculations, we conclude that besides dissociating the Mg–H complex by forming H2O, annealing in O2 has another positive effect on the activation of acceptor Mg in GaN. Mg can be further activated by the formation of an impurity band above the valence band maximum of host GaN from the passivated MgGa–ON complex. Our calculated ionization energy for acceptor Mg in the passivated system is about 30 meV shallower than that in pure GaN, in good agreement with previous experimental measurement. Our model can explain that the enhanced electroluminescence intensity of InGaN/GaN MQWs based on Mg-doped p-type GaN is due to a decrease in the ionization energy of Mg acceptor with the presence of oxygen. [ABSTRACT FROM AUTHOR]

InGaN/GaN multi-quantum-well blue (461±4 nm) light emitting diodes with higher electroluminescence intensity are obtained by postgrowth thermal annealing at 720 °C in O2-ambient. Based on our first-principle total-energy calculations, we conclude that besides dissociating the Mg–H complex by forming H2O, annealing in O2 has another positive effect on the activation of acceptor Mg in GaN. Mg can be further activated by the formation of an impurity band above the valence band maximum of host GaN from the passivated MgGa–ON complex. Our calculated ionization energy for acceptor Mg in the passivated system is about 30 meV shallower than that in pure GaN, in good agreement with previous experimental measurement. Our model can explain that the enhanced electroluminescence intensity of InGaN/GaN MQWs based on Mg-doped p-type GaN is due to a decrease in the ionization energy of Mg acceptor with the presence of oxygen. [ABSTRACT FROM AUTHOR]

Green InGaN/GaN multiple quantum wells light-emitting diodes with graded superlattice (GSL) AlGaN/GaN inserting layer are investigated numerically and experimentally. Our simulation results indicate that GSL inserting layer can decrease the effective barrier height of holes by 57 meV, which makes holes more easily inject into the quantum wells. The piezoelectric polarization field near the last barrier is suppressed effectively by introducing of the GSL inserting layer. As a result, the efficiency droop radio is improved from 35.8% to 19.4% at current density of 100 A/cm-2. [ABSTRACT FROM AUTHOR]