Improving light extraction efficiency by <i>p</i>-orbital tuning in multifaceted AlGaN multiple quantum wells

In this work, a multifaceted AlGaN multiple quantum well (MQW) structure with a record-breaking quasi-internal quantum efficiency of 93.9% was achieved. Carrier localization was achieved by engineering the bandgap and optimizing the epitaxial growth of compositionally graded Ga-rich quantum wells on semipolar microfacets, thereby enhancing carrier diffusion toward these active regions and inducing spatially localized deep ultraviolet (DUV) emission. Concurrently, light extraction in the direction perpendicular to the semipolar plane was significantly improved, resulting in dominant transverse electric (TE)-polarized emission. The uniform angular distribution of TE-mode photons was elucidated via first-principles calculations, revealing a donut-shaped p-orbital configuration in the semipolar MQWs. This MQW configuration demonstrates significant potential for revolutionizing high-efficiency DUV optoelectronics through the synergistic carrier localization and controlled polarized emission.