Bidimensional Carrier Modulation in Nanocolumn‐Array AlGaN p‐i‐n Ultraviolet Photodiodes: Achieving External Quantum Efficiency Over 1000%

Abstract High‐sensitivity, low‐power ultraviolet (UV) detection remains a major challenge in optoelectronics, with complex physical mechanisms requiring exploration as devices transition from thin‐film to low‐dimensional structures. Herein, a high‐performance AlGaN p‐i‐n ultraviolet photodetector featuring a vertical nanocolumn‐array architecture is presented. The device demonstrates an exceptional external quantum efficiency of 1090% and a high responsivity of 3 A W −1 at 0 V, significantly showcasing bidimensional carrier modulation capability. In the longitudinal dimension, the polarization field boosts carrier impact ionization within the confined AlGaN nanocolumns, achieving substantial linear gain. In the transverse dimension, acceptor surface states induce Fermi‐level pinning, forming a surface electron barrier that directs more electrons into the bulk nanocolumn while facilitating hole migration to the surface. This mechanism significantly enhances the separation and extraction of photogenerated carriers. Leveraging excellent linear response, single‐pixel UV imaging capabilities are successfully realized. This novel UV photodetector, with its bidimensional carrier modulation mechanism, paves the way for the development of advanced electronic devices.