Study of polarization field in GaN-based blue LEDs on Si and sapphire substrate by electroluminescence

The electroluminescence spectra of GaN-based light-emitting diodes on Si and sapphire substrate have been investigated as a function of the current density. The experimental results on dependence of the electroluminescence peak wavelength on operating current density can be explained in terms of the competition mechanism between polarization field, carrier screening, band-filling and thermal effect. The polarization field in the active layer of InGaN/GaN multiple quantum wells was estimated to be 105 V/cm by means of carriers screening the polarization field.