Energy Diagram and Recombination Mechanisms in InGaN/AlGaN/GaN Heterostructures with Quantum Wells

Electroluminescence spectra of GaN based LEDs are analyzed quantitatively using a model of 2D density of states with band tails. Calculations take into account an energy diagram with given band offsets between AlGaN, InGaN and GaN layers. The model describes spectral shapes with four fitting parameters in a wide range of currents and intensities with a good accuracy. Fluctuations of well thickness (heterointerface roughness), of In content, of charged impurities and piezoelectric fields are discussed for an evaluation of the exponential tail parameter of 2D density of states in the active region. Spectral maxima move with current changes due to the filling of the band tails and redistribution of current carriers between regions with a larger probability of radiative recombination. 2D concentrations and lifetimes of minority carriers in active layers are evaluated from the parameters of the model.