Observation of applied bias-dependent dot-like luminescence in GaInN-based light-emitting diodes

• Forward and reverse bias-induced dot-like luminescence would be affected by crystal defect-related leakage currents.
• The intensity of reverse dot-like luminescence increases with the reverse leakage current.
• The region of forward dot-like luminescence is in a very different place to that of reverse dot-like luminescence.
• The region of reverse dot-like luminescence is related to screw dislocations as an NRCs.

Forward and reverse bias-induced dot-like luminescence was investigated by evaluating the X-ray rocking curve, micro-photoluminescence (PL), and micro-electroluminescence (EL) of GaN-based light-emitting diodes (LEDs) grown on a normal sapphire substrate (NSS) and a patterned sapphire substrate (PSS). The current–voltage (I–V) characteristics indicated that the forward and reverse leakage currents of the PSS-based LEDs were lower than those of the NSS-based LEDs, which was consistent with the forward and the reverse bias-induced dot-like luminescence densities. These results show that both types of dot-like luminescence are affected by crystal defect-related leakage currents. The micro-PL intensity of the reverse bias-induced dot-like emission region was lower than that of the normal region, whereas the PL intensity of the forward bias-induced dot-like emission region was equal to that of other normal region. In particular, the forward and reverse bias-induced dot-like luminescence was observed in different regions, indicating that the evolutions of the dot-like luminescence under the reverse and the forward bias originated from defect-related leakage paths as nonradiative and radiative recombination centers, respectively.

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