Dislocation-related trap levels in nitride-based LEDs

Deep Level Transient Spectroscopy was performed on InGaN/GaN multiple quantum well (MQW) light emitting diodes (LEDs) in order to determine the effect of the dislocation density on the deep intragap electronic levels. The LEDs were grown by Metalorganic Vapor Phase Epitaxy (MOVPE) on GaN templates with a high dislocation density (HDD) of 8x109 cm-2 and a low dislocation density (LDD) of 3x108 cm-2. Three trapping levels for electrons were revealed, named A, A1 and B, with energies EA ≈ 0.04 eV, EA1 ≈ 0.13 eV and EB ≈ 0.54 eV, respectively. The trapping level A has a much higher concentration in the LEDs grown on the template with a high density of dislocations. The logarithmic dependence of the peak amplitude on the bias pulse width for traps A and A1 identifies the defects responsible for these traps as associated with linearly arranged defects. We conclude that traps A and A1 are dislocation-related intragap energy levels.