Analysis of parasitic cyan luminescence occurring in GaInN blue light-emitting diodes

GaInN blue light-emitting diodes (LEDs) emitting at 445 nm exhibit a spatially uniform cyan emission (480 nm) that dominates the emission spectrum at low injection current. Photoluminescence using resonant optical excitation shows that the cyan emission originates from the active region. The blue-to-cyan intensity ratio, which depends on the electrical and optical excitation density, reveals that the cyan emission is due to a transition from the conduction band to a Mg acceptor having diffused into the last-grown quantum well of the active region. The Mg in the active region provides an additional carrier-transport path, and therefore can explain the high subthreshold forward leakage current that is measured in these LEDs.