Current and optical low-frequency noise of GalnN/GaN green light emitting diodes

摘要

We report on the low-frequency current and light noise in 515 nm green GalnN/GaN quantum well LEDs. The current noise was the superposition of the 1/fand the generation-recombination (GR) noise. The characteristic time of the GR process was found to be proportional to the reciprocal current for the entire current range. This dependence is the characteristic for the monomolecular non-radiative recombination.The dominance of the nonradiative recombination is in agreement with the measured low external quantum efficiency (EQE) < 10%. Hence, the noise measurements point out that a low EQE is caused by the low internal quantum efficiency and not by an inefficient light extraction. The noise spectra of light intensity fluctuations were close to the 1/f noise and correlated with the LED quantum efficiency and with the recombination current. Higher noise corresponded to a smaller quantum efficiency and to a higher non-radiative recombination current. The relative spectral noise densities of the light intensity fluctuations within the LED spectral line increase with the wavelength decrease. Fluctuations at different wavelengths are found to be correlated.