Enhancing the Hole-Injection Efficiency of a Light-Emitting Diode by Increasing Mg Doping in the p-AlGaN Electron-Blocking Layer

By increasing the Mg-doping level and hence the hole concentration in the p-AlGaN electron-blocking layer (EBL), particularly around the interface between the EBL and the top quantum barrier (QB), of a light-emitting diode (LED), the polarization field in this layer can be screened for reducing the potential barrier of hole and hence enhancing the hole-tunneling efficiency such that the overall LED emission efficiency is increased. The increase of Mg-doping level is implemented based on an Mg preflow growth technique, in which Mg source is supplied into the metalorganic chemical vapor deposition chamber for several minutes before the growth of p-AlGaN or p-GaN. It is found that by increasing the Mg-doping level by ~20 times near the interface between the EBL and the top QB, LED emission intensity can be enhanced by ~9.4 times. Based on a simulation study, we observe that the energy difference between the valence band edge and the quasi-Fermi level of hole in the EBL is reduced by increasing the Mg-doping level in this layer such that the total hole density in the quantum wells is increased for enhancing the LED emission efficiency.