GaN-Based Multiquantum Well Light-Emitting Diodes With Tunnel-Junction-Cascaded Active Regions

We report the fabrication of GaN-based multiquantum well light-emitting diode (LED) with tunnel-junction (TJ)-cascaded active region. It was found from X-ray diffraction spectra that crystal quality of the TJ LED was almost identical to that of the conventional LED. Compared with the conventional LED, it was found that we could achieve 35% higher output power from the TJ LED due to the repeated use of electrons and holes for photon generation. It was also found that the external quantum efficiency drooped by 26.3% and 18.7% for the TJ LED and the conventional LED, respectively, as we increased the injection current density to 80 A/cm². Furthermore, it was found that forward voltages measured with an injection current density of 20 A/cm² were 8.94 V for the TJ LED. The large forward voltage observed from the TJ LED should be attributed to the large TJ resistance.