Leakage of holes induced by Si doping in the AlGaN first barrier layer in GaN/AlGaN multiple-quantum-well ultraviolet light-emitting diodes

The electroluminescence characteristics of GaN/AlGaN multiple-quantum-well ultraviolet light-emitting diodes (LEDs) with different concentrations of silicon impurities in the first AlGaN barrier layer near the N-type GaN region is investigated numerically. It is found that the LED's electroluminescence spectrum blueshifts and its peak intensity increases first and then decreases, as the Si-doping concentration increases. This is because that the effective potential height and width of the first barrier layer is reduced due to the screening effect by the ionization of silicon impurities. As a result, more electrons can be injected into the active region, enhancing the luminescence efficiency. However, when the impurity concentration is too high, the leakage of holes may become severe, leading to a reduction of the luminescence intensity for the most heavily doped sample at the injection current of 20 mA.