Efficient and droop-free AlGaN-based UV-C LED using the inverted linearly graded active region and engineered hole source layer

Abstract

The poor efficiency of the aluminum gallium nitride (AlGaN)-based ultraviolet (UV)-C light emitting diode (LED) remains as the major hindrance towards its commercialization. Thus, to enhance the internal quantum efficiency (IQE) and light output power (LOP) and to mitigate the efficiency droop of AlGaN-based UV-C LED, this simulation work proposes and examines a new engineering strategy, i.e., inverted linearly graded quantum wells along with quantum barriers over a series of samples A, B and C. To further improve the characteristics of AlGaN-based UV-C LED, an engineered linearly graded p-AlGaN layer has been proposed in the device structure. This increases the electron and hole concentrations by ∼2-fold and ∼8-fold, respectively. The 1.2-fold reduction in hole effective potential barrier height improves the hole injection. Also, the 1.5-fold increase in electron effective potential barrier height limits electron spill-off from the active region. The proposed structural-engineering reduces quantum confined stark effect (QCSE) confirmed by the reduction of quantum well slopes. Reducing carrier spill-off and QCSE increases average radiative recombination rate by ∼8-fold. The maximum IQE is improved by ∼44 % and the efficiency droop is also reduced to a promising level of ∼2 % in case of the sample under consideration. Finally, the LOP increases 10-fold, promisingly. Thus, the proposed structure is supposed to be highly potential for improving the UV-C LED performance. The electroluminescence spectra show that despite the gradual differences introduced in the structure, all the samples emit at ∼276 nm with similar full width at half maximum providing a reference for the comparison.