In order to improve the hole injection efficiency of GaN based multiple quantum wells LED by utilizing V-pits,mini-LEDs with different structures of last quantum barrier(LQB)layer were fabricated.The LQB structures of the four samples are GaN(10 nm),AlN(10 nm),Al0.14Ga0.86N(10 nm),and GaN(8.6 nm)/AlN(1.4 nm),re-spectively.The recombination mechanisms were studied in these samples with low-temperature electroluminescence spectra,and further validations were carried out through current voltage characteristics testing.The results indicate that a larger proportion of holes transported to deeper quantum wells in samples with AlGaN or GaN/AlN LQB.Exper-imental results show that the main reason of this improvement is the increasing proportion of holes injected through sidewall quantum wells of V-pits due to the suppression of hole injection through the c-plane MQWs,thereby enhanc-ing hole injection efficiency.LEDs with GaN/AlN LQB exhibit lower forward voltage and higher luminous efficiency.On the other hand,a larger V-pits transport ratio can increase the non-radiative recombination rate,whereas limits the efficiency of samples with AlGaN LQB.We conducted a detailed study on the carrier transport mechanisms and the roles of V-pits in GaN based LED devices.
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