Competing processes in nitride alloys in MQWs of LEDs

The nature of competing processes leading to narrowing and broadening of the electroluminescence spectra width at half maximum under the injection current in nitride LEDs emitting at wavelengths of 270–280 nm and 530–540 nm  has been studied. It was found out that there may be local regions with disturbed stoichiometry of random alloy fluctuations, enriched in excited defects (“deep center + local vibrations”) in nitride MQWs with random alloy fluctuations.  The capture of injected charge carriers by such defects in MQWs located in the space charge region of the pn junction was shown to lead to their coordination rearrangement in the lattice. This also results in a more equilibrium state  of random alloy fluctuations and is accompanied by a narrowing of the full width at half maximum electroluminescence spectrum. However, this mechanism is a source of carrier loss that reduces the external quantum efficiency of  LEDs at the maximum. It was shown experimentally that the higher the level of disorder in random alloy fluctuations, the lower the external quantum efficiency values. The nonequilibrium filling of the lateral random allow fluctuation by  charge carriers in MQWs located outside the space charge region causes the broadening of the full width at half maximum electroluminescence spectrum in LEDs. This mechanism leads to a drop in external quantum efficiency at current densities j > 30 A/cm².