Freestanding Oxide-Based UV Photodetectors with Mechanically Tunable Performance.

Abstract

Ultraviolet (UV) detectors based on Schottky junctions offer advantages such as high detectivity, low noise, and suppressed dark current. Enhancing the Schottky barrier height (SBH) is critical for reducing the dark current and boosting the overall device performance. While the flexoelectricity effect has recently emerged as a promising strategy for SBH modulation in 2D material-based detectors, its application to oxide-based devices is limited by substrate-induced mechanical constraints. Here, we demonstrate a freestanding ZnO Schottky photodetector that exploits electromechanical coupling─including both piezoelectric and flexoelectric contributions─to modulate the SBH and enhance the UV detection performance. As the applied force increases, the SBH is elevated from 0.48 to 0.57 V, leading to a substantial enhancement in responsivity from 10 mA·W^-1 to 678 mA·W^-1 and detectivity from 3.7 × 10⁹ Jones to 7.9 × 10¹¹ Jones. These findings highlight the potential of strain engineering in freestanding oxide semiconductors for developing high-performance, mechanically tunable UV photodetectors.