Alleviated built-in electric field in the active region of AlGaN deep-ultraviolet light-emitting diodes with locally embedded p-i-n junctions

Abstract

The strong polarization-induced electric field in the multi-quantum well region reduces the radiative recombination rates by separating the electron and hole wave functions, which is one of the most detrimental factors that is to blame for the low luminous efficiency of AlGaN deep-ultraviolet light-emitting diodes (DUV LEDs). In this work, we redesigned the active region by incorporating Si and Mg doping at the vicinity of the quantum wells, forming a series of embedded p − i − n junctions in the multi-quantum well region. The additional electric field induced by the fixed charges from the embedded doping-induced junctions can effectively compensate for the intrinsic polarization-induced electric fields in the quantum well region and give rise to the improved overlap of hole and electron wave function, hence enhancing the radiative recombination rates and the external quantum efficiency and optical power of DUV LEDs. The mechanism behind the alleviated polarization electric field is comprehensively discussed and analyzed. The embedded p − i − n junctions can also alter the band diagram structure of the active region, decrease the effective barrier heights for holes, and diminish the electron leakage into the p -type region. In addition, different thicknesses and doping concentrations of the embedded p - and n - layers were designed, and their influence on the performance of DUV LEDs was numerically analyzed. The proposed structure with embedded p − i − n junctions provides an alternative way to achieve efficient DUV LEDs.