Performance enhancement of 254 nm DUV LEDs utilizing tunnel junction contact layer and asymmetric...

Deep ultraviolet light-emitting diodes (DUV LEDs) operating at 254 nm face significant challenges in achieving efficient hole injection, resulting from the low p-type doping efficiency of high-Al-content AlGaN and the consumption of holes caused by severe electron leakage. To address these issues, a 45-nm-thick tunnel junction (TJ) contact layer (CL) is introduced to enhance hole generation. Furthermore, an asymmetric polarization-induced doping (PID) electron blocking layer (EBL) is proposed to suppress electron leakage. The performance of a conventional DUV LED, a DUV LED with 25-nm-thick TJ CL, a DUV LED with 45-nm-thick TJ CL, a DUV LED with 45-nm-thick TJ CL and V-shaped EBL, a DUV LED with 45-nm-thick TJ CL and symmetric PID EBL, and a DUV LED with 45-nm-thick TJ CL and asymmetric PID EBL is simulated using the advanced physical model of semiconductor devices (APSYS) software. The results indicate that incorporating a 45-nm-thick TJ CL enhances hole generation and reduces turn-on voltage. However, without an optimized EBL, severe electron leakage persists in the DUV LED with a 45-nm-thick TJ CL. The utilization of an asymmetric PID EBL increases the effective barrier height in the conduction band for electrons while reducing it in the valence band for holes. As a result, electron leakage is effectively suppressed, and hole injection is enhanced. Due to the increased carrier injection, the DUV LED with a 45-nm-thick TJ CL and an asymmetric PID EBL exhibits the highest radiative recombination and spontaneous emission rate. At an injection current of 75 mA, the internal quantum efficiency (IQE) reaches 25.1%, while the output power increases to 6.0 mW. In conclusion, the combination of a 45-nm-thick TJ CL and an asymmetric PID EBL offers a theoretically effective approach to mitigating the issue of insufficient hole injection in 254 nm DUV LEDs.