Ultrahigh-Responsivity Ultraviolet Phototransistor Enabled by Ferroelectric Gating Enhancement Based on an AlGaN/GaN HEMT

The development of high-performance ultraviolet (UV) photodetectors is often constrained by a fundamental tradeoff between responsivity, response speed, and power consumption, limiting their overall performance. Here, we demonstrate a device paradigm that addresses this challenge by integrating a Bi ${}_{{3}.{25}}$ La ${}_{{0}.{75}}$ Ti₃O₁₂ (BLT) ferroelectric gate dielectric with an AlGaN/GaN high-electron-mobility transistor (HEMT). The design leverages a nonvolatile polarization field of the ferroelectric material in tandem with an external electric field to modulate the 2-D electron gas (2DEG) channel, offering a unique mechanism for fine-tuning optoelectronic performance. Benefiting from this ferroelectric gating enhancement, the BLT-gated phototransistor exhibits outstanding and well-balanced characteristics, including an ultrahigh responsivity of $2.13\times 10^{{6}}$ A/W, a specific detectivity of $9.36\times 10^{{14}}$ Jones, and rise/fall times of 0.38/2.84 s. The device can also detect weak UV light at 360nm with an illumination intensity as low as $2~\mu $ W/cm². This work demonstrates a novel approach for electrically tuning responsivity via ferroelectric poling, offering a promising pathway toward high-performance UV phototransistors. These findings advance the design of UV photodetectors with balanced performance for a wide range of practical optoelectronic applications.