Aluminum Plasmonics Enriched Ultraviolet GaN Photodetector with Ultrahigh Responsivity, Detectivity, and Broad Bandwidth.

Abstract

Plasmonics have been well investigated on photodetectors, particularly in IR and visible regimes. However, for a wide range of ultraviolet (UV) applications, plasmonics remain unavailable mainly because of the constrained optical properties of applicable plasmonic materials in the UV regime. Therefore, an epitaxial single‐crystalline aluminum (Al) film, an abundant metal with high plasma frequency and low intrinsic loss is fabricated, on a wide bandgap semiconductive gallium nitride (GaN) to form a UV photodetector. By deliberately designing a periodic nanohole array in this Al film, localized surface plasmon resonance and extraordinary transmission are enabled; hence, the maximum responsivity (670 A W−1) and highest detectivity (1.48 × 1015 cm Hz1/2 W−1) is obtained at the resonance wavelength of 355 nm. In addition, owing to coupling among nanoholes, the bandwidth expands substantially, encompassing the entire UV range. Finally, a Schottky contact is formed between the single‐crystalline Al nanohole array and the GaN substrate, resulting in a fast temporal response with a rise time of 51 ms and a fall time of 197 ms. To the best knowledge, the presented detectivity is the highest compared with those of other reported GaN photodetectors.