Enhanced Carrier Injection in AlGaN-Based Deep Ultraviolet Light-Emitting Diodes by Polarization Engineering at the LQB/p-EBL Interface

The external quantum efficiency (EQE) of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) is still far from satisfactory due to the main issues of electron leakage and insufficient hole injection. The positive sheet charges generated by polarization at the interface between the last quantum barrier (LQB) and the p-type electron blocking layer (p-EBL) can induce electron accumulation and hole depletion in the vicinity of this interface, leading to electron leakage and hindering the hole injection. In this paper, we propose an Al-composition-increasing AlGaN layer (ACI-AlGaN) inserted between the LQB and p-EBL to enhance the carrier injection ability of DUV LEDs via modulating the sheet charges generated by polarization at the LQB/EBL interface and the underlying mechanism was analyzed by numerical calculation. The inserted structure can eliminate the positive sheet charges at the p-side interface of LQB and induce hole accumulation in the vicinity of the n-side interface of p-EBL, which can subsequently reduce electron leakage and favor hole injection respectively. The proposed DUV LED structure with an ACI-AlGaN layer exhibited enhanced EQE by 45.7% and its forward voltage maintained undegraded. This design scheme can provide an alternative way to promote the performance of DUV LEDs with a variety of applications.