Boosting external quantum efficiency of AlGaN-based deep-ultraviolet LEDs enabled by heuristic optimization-based inverse design

Abstract

In this study, with the aim of concurrently enhancing the internal quantum efficiency (IQE) and light extraction efficiency (LEE) of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs), thus boosting the external quantum efficiency (EQE), a novel method for the inverse design of step-like quantum wells (QWs) and superlattice electron blocking layers (SL EBLs) based on intelligent optimization algorithms is put forward. Initially, an optimization problem aimed at maximizing EQE regarded as the product of IQE and LEE is formulated. The Al composition and thickness gradient of the step-like QWs, along with the Al composition gradient of the SL EBL, are set as decision variables. An intelligent optimization algorithm is then utilized to address this optimization problem. The results demonstrate that, based on the optimized structure, the overlap of the carrier wave functions in the active region of the DUV LED is significantly increased, which can effectively mitigate electron leakage and promote hole injection, thus enhancing the IQE. Moreover, the optimized structure increases the TE-polarization percentage, which results in an improved LEE. As a result, the optimized structure shows a 32 % and 9.7 % increase in IQE and LEE, respectively, at an injection current density of 200 A/cm², and the EQE exhibits a remarkable 45 % improvement.