Enhanced hole injection in Ga-polar 290 nm AlGaN-based DUV LEDs with a p-n junction hole accelerator

Abstract

The limited kinetic energy of holes in AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) poses a challenge in their transportation into the active region across the Al-rich electron blocking layer (EBL) and significantly restricts the electrical and optical performance of DUV LEDs. In this work, we propose a hole accelerator structure composing a p-AlxGa1-xN/n-AlxGa1-xN junction to improve the hole injection efficiency and explore the mechanism behind the enhanced performance with the Advanced Physical Models of Semiconductor Devices software (APSYS). The built-in electric field of the p-n junction distributes along the [000-1] direction, which can enhance the hole drift velocity and improve the hole injection into the active region. Moreover, with an optimum Al composition of 50%, [000-1] oriented polarization-induced electric field can be generated at the vicinity of both the p-EBL/accelerator and accelerator/hole supplier interfaces, which further boosts the holes into the active region. Besides, the original steep barrier for holes at the EBL/hole supplier interface can be splited into a two-step barrier which is more favorable for hole transportation. As a result, an enhanced optical power by 49.4% and alleviated efficiency droop by 76.3% can be achieved with the proposed p-n junction-based hole accelerator. The results can pave the way for AlGaN-based DUV LEDs towards high-power and high-efficiency applications.