Investigation into the Distribution of Built-in Electric Fields in LED Heterostructures with Multiple GaN/InGaN Quantum Wells by Electroreflectance Spectroscopy

Abstract

Electric-field nonuniformity in the active region of a LED (light-emitting diode) heterostructure based on five identical GaN/InGaN quantum wells is investigated by the electroreflectance method. The energies of band-to-band transitions in the quantum wells and barriers are determined from the analysis of electroreflectance spectra using the Kramers–Kronig transforms. The procedure for estimating the electric-field strength in separate quantum wells of the active region by the position of spectral lines is proposed. It is found that the energies of the main transition in quantum wells of the active region with zero bias of the p–n junction differ by a magnitude on the order of 140 meV, which corresponds to a difference in the electric-field strengths of 0.78 MV/cm. It is shown that the nonuniformity of the electric field in the active region depends on the p–n junction bias.