By increasing the Mg-doping level and hence the hole concentration in the p-AlGaN electron-blocking layer, 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 pre-flow 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. 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. Based on this technique, the high performance of an LED with the total p-type thickness as small as 38 nm is demonstrated. The surface plasmon coupling effects, including the enhancement of internal quantum efficiency, increase of output intensity, reduction of efficiency droop, and increase of modulation bandwidth, among the thin p-type LED samples of different p-type thicknesses are compared. These advantageous effects are stronger as the p-type layer becomes thinner. With a circular mesa size of 10 micron in radius, we achieve the record-high modulation bandwidth of 625.6 MHz among c-plane GaN-based LEDs.
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