Optical Polarization Modulation for AlGaN-Based Far-UVC MQWs by Built-in Electric Field Regulation

AlGaN-based deep ultraviolet (DUV) light-emitting diodes with peak wavelengths below 250 nm (far-UVC) have attracted significant attention. The issue of reduced light extraction efficiency (LEE), mainly caused by predominant transverse magnetic polarized light emission, still remains unresolved. Here, we propose regulating the light-emission polarization property of far-UVC multi-quantum-wells (MQWs) using built-in electric fields. By doping Si into the MQW barriers, the built-in electric field in the wells is modified, achieving an adjustable degree of polarization from 0.26 to 0.42. It is observed that as the built-in electric field increases, the heavy hole subband in the wells approaches the valence band edge related to the crystal field split-off hole (CH) subband, but the wave function overlap between conduction band electrons and HH subband holes decreases related to that between CBEs and CH subband holes. As the electric field in the wells lifts, the transverse electric emission proportion initially rises and then falls. It is because the built-in electric field can alter the quantum confinement effect and the carrier spatial distribution. This work provides a novel method for controlling the optical polarization of AlGaN-based far-UVC MQWs, thereby enhancing LEE.